René Redzepi and Lars Williams at UCLA - Photo by Amy Scattergood at LA Weekly

Monday May 7, René Redzepi from noma and our Lars Williams presented a lecture at UCLA – The Exploration of Deliciousness. It is part of the Science and Food Lecture Series at UCLA

For those of us not present, these events naturally causes envy. However, you can all get a peak into what went on thanks to LA weekly blogs, that gives a vivid impression of the enthusiasm the presenters and audience showed. Enjoy.

This is a copy of the Nordic Food Lab’s first scientific article, accepted in the fantastic publication, Flavour Journal (flavourjournal.com)  Take a look at the other articles, covering a wide breadth of topics, all fascinating. We were in London last week for the launch, and would like to thank Ben, Nandita and the whole Biomed staff for a great event. We are currently working on a few articles (beyond our normal ravings) with the requisite academic rigor for upcoming publication- stay tuned.

Seaweeds for umami flavour in the New Nordic Cuisine

Flavour 2012, 1:4 doi:10.1186/2044-7248-1-4

The electronic version of this article is the complete one and can be found online at:http://www.flavourjournal.com/1/1/4

© 2012 Mouritsen et al; licensee BioMed Central Ltd.

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Use of the term ‘umami’ for the fifth basic taste and for describing the sensation of deliciousness is finding its way into Western cuisine. The unique molecular mechanism behind umami sensation is now partly understood as an allosteric action of glutamate and certain 5′-ribonucleotides on the umami receptors. Chefs have started using this understanding to create dishes with delicious taste by adding old and new ingredients that enhance umami. In this paper, we take as our starting point the traditional Japanese soup broth dashi as the ‘mother’ of umami and demonstrate how dashi can be prepared from local, Nordic seaweeds, in particular the large brown seaweed sugar kelp (Saccharina latissima) and the red seaweed dulse (Palmaria palmata), possibly combined with bacon, chicken meat or dried mushrooms to provide synergy in the umami taste. Optimal conditions are determined for dashi extraction from these seaweeds, and the corresponding glutamate, aspartate and alaninate contents are determined quantitatively and compared with Japanese dashi extracted from the brown seaweed konbu (Saccharina japonica). Dulse and dashi from dulse are proposed as promising novel ingredients in the New Nordic Cuisine to infuse a range of different dishes with umami taste, such as ice cream, fresh cheese and bread.

Keywords:

umami; seaweed; dashi; glutamate; kelp; dulse; New Nordic Cuisine

Authors’ summary for chefs

Herein we review the concept of umami and deliciousness in a historical context and describe recent advances in the scientific understanding of the sensory perception of umami and the involved taste receptors. The primary stimulatory agent in umami is the chemical compound glutamate, which is found in large amounts in the Japanese seaweed konbu, which is used to prepare the soup broth dashi. We have explored the potential of local Nordic seaweeds, in particular sugar kelp and dulse, for dashi production and have discovered that dulse is high in free glutamate and hence a good candidate for umami flavouring. We describe methods by which to optimise the umami flavour using sous-vide techniques for extraction of the seaweeds, and we demonstrate how dulse dashi can be used in concrete recipes for ice cream, fresh cheese and sourdough bread.

Background

Although umami was suggested as a basic taste in 1908 by the Japanese chemist Kikunae Ikeda[1], umami only caught on very slowly in the Western world [2-5]. Being a verbal construction to describe the essence of delicious taste (‘umai’ (旨い) is delicious, and ‘mi’ (味) is essence, inner being or taste), the term ‘umami’ was coined by Ikeda to signify a unique and savoury taste sensation that should be ranked as the fifth basic taste along with the four classical basic taste modalities: sour, sweet, salty and bitter. In the past couple of decades, along with the globalisation of the Asian kitchen, and in particular the Japanese kitchen, umami is being used more commonly in a culinary context among chefs [6,7] and food scientists [8]. The term has now entered the diverse world of cooking recipes and has been the main topic of a couple of cookbooks [9,10] and most recently a popular science book [11].

Ikeda based his suggestion of umami as a specific taste on the discovery of a particular substance, monosodium glutamate (MSG), which he found in large quantities in free chemical form in one of the key ingredients that enters dashi, the soup stock behind all Japanese soups.Dashi is made by a warm extract of the large brown Japanese seaweed konbu (Saccharina japonica). This extract is called konbu dashi. To the konbu dashi is then added a particular, highly processed fish product, katsuobushi, leading to the so-called first dashi (ichiban dashi). Ikeda discovered that konbu contains about 2 to 3 g of free MSG per 100 g dry weight of konbu [1]. Whereas a lot of processed foods, in particular fermented products, can contain as much MSG as, and even more than, konbu [3,12-16], no other unprocessed, raw organic material is known to contain more free MSG than konbu. In addition to linking MSG to umami, Ikeda immediately realised the technological importance of his discovery as a means to produce artificial flavouring agents to foodstuff, leading the way to the establishment of the international company Ajinomoto (Tokyo, Japan) [17]. MSG is now used across the world as a flavouring enhancer, potentiator and additive in a wide variety of foodstuff [14]. In Europe, it has to be declared as E621 on food product labels.

There are several reasons for the slow acceptance of umami as a basic taste in the Western world. First, in contrast to Japanese cuisine, there is no single common ingredient in Western cuisines that provides as clean a sensation of umami as dashi, whereas Western cuisine has kitchen salt (sodium chloride) for salty, ordinary table sugar (sucrose) for sweet, quinine for bitter and acid for sour. Second, cultural differences imply fundamental differences in taste description and codability of taste [18]. Third, the taste sensation of pure MSG appears to be different in different individuals, probably because umami interacts strongly with sweet and salty [19,20]. This has led to confusion regarding MSG’s being the source of a unique taste or simply a taste enhancer [21]. Fourth, a shear resistance to accept a new basic taste without a scientifically established sensational physiological basis probably also has played a role, certainly among food scientists and neurophysiologists.

A breakthrough came in 2000 when the first umami receptor was discovered [22]: the metabotropic glutamate receptor taste-mGluR4, which is a special dimeric G protein-coupled receptor [23] located in the membranes of the taste cells in the taste buds. Taste-mGluR4 is a truncated version of the well-known glutamate receptor mGluR4 in the brain, and it is selectively sensitive to L-glutamate. Since then, two other umami receptors have been found: T1R1/T1R3[24,25] and a special mGlu receptor [26] that is related to the brain glutamate receptor mGluR1. It remains unclear whether the different umami receptors use different signalling pathways[27,28].

The T1R1/T1R3 receptor is particularly interesting for an informed, molecularly based use of umami in the kitchen. In contrast to taste-mGluR4, which is sensitive only to L-glutamate, T1R1/T1R3 is also strongly stimulated by certain 5′-ribonucleotides, in particular inosinate (inosine-5′-monophosphate, IMP) and guanylate (guanosine-5′-monophosphate, GMP), which in a synergistic fashion potentiate the receptor’s sensitivity to glutamate. This type of synergy in umami taste has been known phenomenologically for centuries in Japanese cuisine, and the first scientific basis for it was provided in 1957 by the Japanese chemist Akira Kuninaka [29]. Building on earlier work by Shintaro Kodama [30], who had found inosinate in katsuobushi, Kuninaka discovered that guanylate from dried shiitake mushrooms or inosinate from katsuobushi enter a synergistic relationship with glutamate from konbu. These synergies underlie classic preparations of dashi [15]. The molecular basis for the synergy in umami sensation has recently been revealed as a cooperative, allosteric binding of glutamate and ribonucleotides on the Venus flytrap motif on the T1R1 part of the T1R1/T1R3 receptor complex ([31] and H Khandelia and OG Mouritsen, unpublished data). Umami also enters an interaction with other tastes, in particular sweet and salty but also bitter, and a particularly complex relationship has been found between the umami receptor and the receptors for sweet and bitter [32]. In addition to glutamate, L-aspartate (monosodium aspartate, MSA) has also been associated with umami, but with much less potency and a still unknown sensory mechanism [19,25].

Although in a much less pure form than in Japanese cuisine, umami also plays a key role in Western cuisine [11]. Many types of food contain large natural amounts of free MSG. The most well-known are Marmite, fish sauces, mature hard cheeses such as Parmesan cheese, blue cheeses, sun-dried tomatoes, anchovy paste, soy sauce, cured ham and so on. Similarly, synergy in umami sensation is used extensively in Western food pairing, such as tomatoes with anchovies, vegetables with meat, eggs with bacon, green peas with scallops, and so on.

The outline of the remaining part of the paper is as follows. First, we describe how dashitraditionally is made from konbu, then we move on to introduce some Nordic seaweed species that are candidates for dashi production. The main core of the paper that follows those sections describes improved methods of dashi production, including in particular production in controlled temperature conditions. Data regarding the content of free glutamate and other amino acids in different seaweed extracts is presented. Moreover, three concrete recipes are provided for dishes that take advantage of the dashi and umami flavours from the red seaweed species dulse that turns out to release large amounts of free glutamate. In the “Discussion” and “Conclusion” sections, we highlight the potential of using seaweed species from local Nordic waters in the New Nordic Cuisine.

Dashi from seaweeds

Classic Japanese cuisine [33] revolves around dashi made from konbu and katsuobushi. In the strictly vegetarian temple kitchen, shōjin ryōri, also known as ‘the enlightened kitchen’ [34], deriving from 12th-century Japan, katsuobushi is replaced by dried shiitake. Konbu provides glutamate and shiitake provides guanylate to replace inosinate from katsuobushi. The synergetic action in umami is even stronger in the pairing of glutamate with guanylate than with inosinate[31,35].

There are several variants of konbu, all of which belong to the algal order Laminariales, withSaccharina japonica being the most commonly used species for dashi. Konbu hence belongs to the same genus as sugar kelp (Saccharina latissima). The blades of konbu can grow to be several metres long and have a maximum width of 10 to 30 cm. Most of the konbu on the world market for human consumption is farmed at lines in the seas around Japan and China. After harvest,konbu is sun-dried and the best quality konbu is aged in cellars (kuragakoi) for from one to ten years, with the typical ageing period being two years. During ageing, the seaweed matures and obtains a milder flavour and a less strong taste and smell of the sea. The umami flavour in dashimade from aged and matured konbu appears to stand out more clearly.

Konbu contains large amounts of free amino acids, of which 80% to 90% are glutamic acid in the form of MSG [3]. Other important free amino acids are alanine and proline, which impart a sweet taste to the seaweed. Konbu does not contain any of the 5′-ribonucleotides that enter synergistically with glutamate in umami. Often some of the free MSG precipitates together with salt and mannitol to form a white layer on the surface of the dried and aged konbu blades. This layer should not be removed before the dashi is extracted from the konbu, because it dissolves readily in water and provides a combination of flavours: umami, salty and sweet. Mannitol is a sweet-tasting sugar alcohol which has about 60% of the relative sweetness of table sugar (sucrose). Mannitol is often found in the Saccharina family, in particularly large amounts in sugar kelp (hence its name). Konbu contains 2 to 3 g of free MSG per 100 g dry weight. With the exception of the pulp of mature tomatoes [36], konbu is possibly the kind of foodstuff that, with the least amount of processing, develops free glutamate in any appreciable amounts.

Of the many different variants of Japanese konbu, ma-konbu, rausu-konbu and rishiri-konbu are considered to be the best for extraction to dashi [10], and they lead to a very light dashi with a mild and somewhat complex taste. Ma-konbu is the konbu with the largest amount of free glutamate, 3,200 mg/100 g, whereas rausu-konbu has 2,200 mg/100 g and rishiri-konbu has 2,000 mg/100 g. The lower-quality hidaka-konbu has 1,300 mg/100 g [10,12]. The red seaweed laver (Porphyra yezoensis) used to produce nori has comparable amounts (1,378 mg/100 g), whereas wakame (Undaria pinnatifida) has very little (9 mg/100 g) [12].

A remarkable feature of dried and aged konbu, as well as a number of other seaweeds, is that the free glutamate in the tissues of the seaweed can be transferred to water by a rather mild, warm extraction process solely involving water. Although there is a substantial variation in the way different chefs prepare konbu dashi, the recipes used generally prescribe soaking the drykonbu in water at room temperature (typically using 10 g of dry konbu per litre of water) for about half an hour, heating it in an open pan to just below the water boiling point at 100°C and then quickly removing the konbu from the water before bitter-tasting compounds seep out. During this procedure, only a relatively small amount of the total free glutamate is released into the water. A typical konbu dashi or ichiban dashi prepared using the traditional Japanese recipe (K Ninomiya, unpublished data from the Umami Information Center, and [37]) contains about 20 to 30 mg of glutamate per 100 g of aqueous dashi extract. The extraction process can be optimised by varying conditions such as extraction temperature and possibly the quality (hardness) of the water used for the extraction. We shall address the optimisation of dashi preparation in this paper and show that by extracting the seaweeds at a lower temperature but for a longer time, a much more flavourful dashi characterised by significantly higher levels of glutamate as well as aspartate can be obtained.

Although konbu is the kind of seaweed that contains the largest percentage of free glutamate, other seaweeds can also provide some umami flavour despite their smaller glutamate content. Laver (Porphyra spp.) that is used to produce the paper-thin nori sheets well-known from maki-zushi [38] contains rather large amounts of free glutamate [12] in addition to some inosinate and guanylate, which enhances the umami flavour in sushi dishes. In fact, nori is the only kind of seaweed that contributes to both basic (glutamate) and synergetic (nucleotides) umami flavour.

Until now, little work has been reported on the use of seaweeds other than konbu for dashipreparations, although it is well-known that seaweeds in general impart delicious flavours to food[39,40]. Moreover, the use of seaweeds for human consumption is little developed in the Western world [41]. To investigate the potential of using local seaweeds from the waters around the Nordic countries for dashi preparations and umami flavouring, we have undertaken quantitative scientific and qualitative gastronomic investigations of dashi extracts from a brown seaweed, sugar kelp (Saccharina latissima), and a red seaweed, dulse (Palmaria palmata). Some preliminary work has also been done on the red seaweed graceful red weed (Gracilaria verrucosa). For comparison, we have simultaneously studied classic dashi prepared from various qualities of Japanese konbu(Saccharina japonica). Our investigations can be seen as an attempt to explore the gastronomic potential of local seaweeds [42] for use in the New Nordic Cuisine [43,44].

The seaweeds

Sugar kelp (Saccharina latissima)

The large, metre-long, brown seaweed (kelp) of the order Laminariales, sugar kelp (Saccharina latissima) is rich in iodine and minerals, in particular calcium, potassium, manganese and iron. It is very common in the sublittoral zones of the cold seas of the North Atlantic Ocean, and it has a strong flavour of the ocean. Its name derives from its distinct sweet taste caused by large amounts of the sugar alcohol mannitol. Sugar kelp can release significant amounts of extracellular polysaccharides, such as alginates, that easily seep out in water extracts, making these undesirably viscous for most gastronomical uses. The tissues of sugar kelp are tougher than those of konbu.

In the present work, we used sugar kelp farmed in Denmark. Both young and old specimens are harvested, and before use for dashi they are all subject to drying. Some samples were also stored and aged for a period of time before use. Specimens of dried, farmed sugar kelp are shown in Figure 1.

Dulse (Palmaria palmata)

Dulse (Palmaria palmata) is a red, intertidal seaweed well-known in the traditional cuisines of Ireland, Scotland and Iceland, as well as along the coasts of North America. It is common in the Atlantic Ocean, where it grows to a size of up to 50 cm. It has thin and delicate purple fronds with simpler polysaccharides than those found in the brown seaweeds, providing dulse with a more delicate flavour and soft texture. When dried, dulse develops hints of liquorice and smoke, and when toasted it has a nutty taste. Although dulse appears to be one of the seaweeds with the more interesting potential for gastronomical applications, it is surprisingly little used in modern cuisine.

In the present work, we used a variety of different supplies of dulse. Some were harvested in the wild in Iceland, and some were farmed in Denmark. All samples were dried before use. A specimen of dried, farmed dulse is shown in Figure 2. This particular specimen has an almost isotropic shape due to its being grown freely in a pool with constantly moving and swirling water. This is in contrast to dulse naturally grown by being anchored on a substrate at the bottom of the sea, which usually leads to a directional, treelike structure of the shape of a hand, as suggested by the Latin name palmata.

Graceful red weed (Gracilaria verrucosa)

This red and stringy seaweed, also called ‘sea moss’ because of its thread-thin fronds, has not been used to date in Western cuisine. It is traditionally used as a sea vegetable, for example, in Hawaii and Japan, where it is called ogonori. Gracilaria is a rich source of agar that is used as a thickening agent. In recent years, it has made its way into the Nordic waters, where it is considered one of the invasive species that threatens domestic marine life. In the present work, we used Gracilaria farmed in Denmark, and all samples were dried before use.

Konbu (Saccharina japonica)

Konbu is a large brown seaweed that is farmed in large quantities in China and Japan, amongst other countries. In these Asian countries it is a common staple in traditional cuisine as a sea vegetable and a source for dashi, and it is also used in a wide range of processed konbuproducts. Konbu is appreciated for its mild and umami flavour and has an interesting and soft texture, despite the considerable thickness of its fronds. Similarly to sugar kelp, konbu is high in iodine. It secretes much less polysaccharide than sugar kelp when extracted from water, and the resulting dashi is light in colour with a fluidity similar to that of pure water. In the present work, we used two commercial supplies of dried Japanese konbu of two distinct qualities: a first-qualityrausu-konbu and a second-quality hidaka-konbu.

Results

The dashi from the seaweeds is prepared as described in ‘Materials and methods’. Figure 3 shows photographic images of samples of dashi prepared from, respectively, konbu (konbu dashi),konbu and katsuobushi (ichiban dashi) and dulse (dulse dashi). The konbu dashi is very light in colour, the ichiban dashi is darker because of colouring from the fermented katsuobushi and the dulse dashi has a light purple colour.

The colours and flavours of the different types of dashi vary quite significantly. The colour and flavour of the sugar kelp dashi differed in relation to the age of the seaweeds and whether they were in a sorus stage. The sorus contains the sporophylls and is the reproductive organ of the seaweed. Dashi prepared from sorus had far less flavour and were lighter in colour than those not in a reproductive cycle. All of the sugar kelp dashi is viscous. With regard to the dulse, there is a distinct difference between dashi from fresher seaweed and that which has been aged. This is evident in the appearance of the original material. The aged seaweed precipitates more salts (including glutamate) on the surface of the fronds in a rather conspicuous manner, and the taste is far stronger and more complex. Therefore, we can conclude that this ageing process is critical for a superior taste and a method employed for producing high-quality konbu.

The difference in the dashi prepared from the two types of konbu is as visually dramatic as it is in taste. The hidaka-konbu produces a dashi with a somewhat greenish hue, with a smell evocative of the term ‘sea vegetable’. The taste is briny, with a slight metallic vegetable tone. In contrast, the rausu-dashi is golden in colour and tastes almost like the chicken bouillon it resembles, very meaty and intense. This taste was amplified when we gently reduced the rausu-dashi in a dehydrator at 60°C, and the stock eventually turned into crispy flakes, as shown in Figure 4. Biting in these flakes was almost as overpowering as biting into a bouillon cube. The konbu-dashiseemed to be the only dashi suitable for this process. The dehydrated dashi from the other types of seaweed became bitter, or unable to fully dry, and it remained sticky.

The different dashi preparations made from the different samples of dried seaweeds were analysed for their full amino acid content and profile, with a focus on glutamate and aspartate, which provide umami flavour, and alaninate, which provides a sweet flavour. The results are shown in Table 1. Figure 5 shows the full amino acid profiles for two types of dashi made fromrausu-konbu and dulse, respectively. We shall return to a discussion of these profiles in the ‘Discussion’ section below and to a comparison of dashi made from different seaweeds as opposed to the use of different extraction techniques.

The data in Table 1 refer to extractions by the techniques introduced in this paper and described in ‘Materials and methods’. It should be noted that the precise amount of amino acids can be very sample-dependent and that the error bars quoted in Table 1 reflect only the estimated uncertainties in the actual amino acid analysis. The data show that rausu-konbu releases very large amounts of free glutamate and aspartate, whereas the levels of alaninate are rather low. The hidaka-konbu provides for about half the amount of glutamate and aspartate compared torausu-konbu. These differences in the umami-producing amino acids reflect the qualitative taste sensations described above and explain why rausu-konbu is considered to be superior to hidaka-konbu for dashi production. In contrast to the differences in umami taste compounds, the two types of konbu release similar amounts of alaninate.

It turns out, somewhat surprisingly, that extraction temperatures of 60°C and 100°C led to similar results with respect to the concentrations of glutamate, aspartate and alaninate in konbu dashi. Also, the softness of the water seems to have had little influence on the concentration of the three amino acids in the dashi extracts studied.

Turning to the dashi prepared from sugar kelp, Table 1 shows that dashi from sugar kelp contains very little of any of the free amino acids analysed, and the results did not depend on whether we used extraction temperatures of 60°C or 100°C. Additionally, the measured amounts are so low that we can find no discernible dependence on the age of the kelp, whether it was matured or not or whether it contained the sorus or not. It is possibly that sugar kelp grown under other nutritional conditions with more nitrogen may contain more glutamic acid and free glutamate than the sugar kelp used for the present study. As noted above, dashi from sugar kelp displays an undesirable viscous behaviour that makes it less suitable as a soup stock.

In contrast to sugar kelp, the data for the dulse dashi in Table 1 show that this red seaweed has an exceptionally good potential for umami flavour. The farmed Danish dulse releases significantly more glutamate and aspartate than the wild Icelandic dulse. In the case of the Icelandic dulse, we measured both young dulse and aged dulse, but found no significant differences in the amount of released amino acids. For none of the dulse samples studied are we able discern any variation in amino acid concentrations for the two different extraction temperatures. Table 1 shows thatGracilaria is a poor source of umami flavours, similar to farmed Danish sugar kelp.

Examples of dishes flavoured by dulse

In this section, we provide some specific recipes using dulse for flavouring dishes developed for the New Nordic Cuisine. The recipes represent a range of novel experiments conducted at the Nordic Food Lab. Photographs of the resulting dishes are shown in Figure 6.

Ice cream with dulse

600 g of dulse-infused milk (infuse at 20 g of dulse/litre of milk)

100 g of cream

80 g of trimoline (inverted sugar syrup)

35 g of sugar

24 g of ColdSwell cornstarch (KMC, Brande, Denmark)

Place the dulse and milk in a plastic bag under vacuum and seal, leaving it in a refrigerator overnight to cold-infuse. Strain the dulse and blend it into a fine purée, and preserve to be added later. Dissolve the sugar and trimoline in a small amount of warmed milk. When cooled, add the milk to the rest of the components, mix thoroughly and freeze the mixture in Pacojet containers. Just before serving, the ice cream is prepared in the Pacojet by high-speed precision spinning and thin-layer shaving to produce a creamy consistency of the ice cream.

The dulse ice cream was conceived to demonstrate the culinary versatility of seaweed in an often unexpected fashion. We chose a low-fat base of almost all milk used, allowing the flavour to emerge. Although there was initial reluctance among some tasters to the idea of seaweed ice cream, the vast majority responded with satisfaction upon actually consuming the ice cream.

The colour of the dulse ice cream is a very pleasing light mauve. The flavour is delicate, light and floral. Some tasters have compared the dulse ice cream with Japanese green tea ice cream, which is indicative of a nuanced, acceptable flavour profile.

We also observed an improvement in texture of the dulse-infused ice cream, which is creamier and smoother than the same ice recipe without dulse. This change in texture is likely caused by the polysaccharides released from the dulse.

Fresh cheese with dulse

1,250 g of dulse-infused milk (infuse at 20 g of dulse/litre of milk)

60 g of cream

25 g of buttermilk

5 g of rennet

Place dulse and milk in a plastic bag under vacuum and seal, leaving it in a refrigerator overnight to cold-infuse. Strain the milk, heat it to 33°C and add the remaining ingredients, including the rennet. Pour the mixture into plastic containers, cover tightly and cook in an oven at 36°C for 45 minutes.

The result is a slightly acidic, fresh cheese with a light tofulike consistency. There is a bit more brininess and more of a rounder seaweed flavour than with the ice cream. Again, there is a desirable improvement in texture and a slightly more elastic, though very pleasant, mouthfeel. This more viscous texture is likely due to carrageenan released from the dulse, which also reduces the cooking time by half.

Bread with dulse

2,500 g of ølandshvede flour, a speltlike wheat species that is high in gluten and protein (13.5%)

500 g of spelt flour

2,200 g of dulse dashi, strained, dulse-minced and reserved

200 g of sourdough starter

50 g of fresh baker’s yeast

60 g of salt

Whisk dashi, starter, yeast and salt together. Add flour and mix at low speed for 5 minutes. Incorporate the minced dulse. Oil a suitable vessel, and proof in a 5°C refrigerator for 24 hours, folding every 8 hours. Shape and allow it to come to room temperature. Bake in an oven at 225°C for 45 minutes.

The dulse sourdough was considered to be a great success. The liquorice, almost fruity tones came forward and added a supportive savoury flavour. The tea tones steamed from a fresh piece of warm bream when torn apart. It was especially excellent with cheese, almost addictive according to many reports from tasters. The crumb seemed quite moist and had excellent texture. The mixing of the bread was quite different from normal, and some care had to be taken not to overmix the dough.

Discussion

The results presented herein provide some quantitative data for amino acid profiles in dashiprepared from Nordic seaweeds, which reveal their potential for providing umami taste. Clearly, the results show that among the studied species, dulse is a much more interesting candidate than sugar kelp and Gracilaria for umami flavouring and dashi. Moreover, the three recipes presented demonstrate in a concrete setting that dulse dashi has a versatile use in the kitchen.

To assess the relative potential of dulse in umami flavouring, we compared the amino acid composition of dashi prepared from dulse with classical dashi on the basis of Japanese konbu. This comparison is provided in Table 2, together with data for two types of chicken soup stock[45,46]. Caution should be exercised when comparing data for the same seaweed species from different sources, because the sample material can be vastly different and the methods of amino acid analysis used and reported in the literature can differ as well. The latter can be particularly troublesome for analysis of extracts of glutamate from brown seaweeds, because it is known that their alginate and salt contents can interfere with the derivation of the amino acids when using classic high-performance liquid chromatography (HPLC) methods [47]. Moreover, different workers have used different amounts of seaweed for their dashi preparations. In the present work, we used about twice the amount of dry seaweed per litre of water compared with many classic Japanese dashi recipes. Still, upon normalising to the same weight ratios, we generally found that the use of the extraction techniques described in the present paper released at least twice as much glutamate and aspartate and up to almost ten times as much alaninate compared to values reported in the literature for konbu (Table 2).

Notwithstanding the above-mentioned difficulties in comparing, on a quantitative basis, the amino acid contents in dashi quoted in reports from different workers, we can compare the contents indashi which we have prepared in the present work using the same weight ratios for seaweed and water and applying the same preparation techniques. As seen in Table 2, we found that dashiprepared by our extraction technique has substantially more umami capacity than dashi prepared by the classic Japanese recipe, which typically involves cold soaking of the konbu for 30 to 60 minutes, followed by warm extraction in a pan and increasing the temperature to just below boiling, then immediately straining the extract. It is well-known that keeping the konbu in the boiling dashi leads to an unpleasantly bitter flavour. More recently, the classic Japanese recipe has been optimised to provide a better flavour and a clearer dashi by heating the solution to only 60°C (as in the present work), but still in an open pan [37]. The many different recipes for preparing classical Japanese dashi probably reflect different preferences among the chefs with respect to the balance between bitter, sweet and umami notes of the extract. The comparison of data in Table 2 between dashi based on various seaweeds and traditional soup stock prepared from chicken meat and vegetables shows that seaweeds may be superior to these meat-vegetable soups with respect to providing compounds that induce umami.

The taste of the dulse dashi is found to be more sweet and complex than traditional konbu dashi. Part of the explanation may be found in the differences in the full amino acid profiles shown in Figure 5. Compared to konbu, dulse releases more of the sweet amino acids alanine, proline, glycine and serine. The dulse extracts also contain small amounts of the bitter-tasting amino acids such as isoleucine, leucine and valine, which may account for the more complex flavour of the dulse dashi. It is noteworthy that the farmed Danish dulse is a serious competitor with hidaka-konbu for umami flavour. One reason may be that the much thinner and delicate fronds of dulse are more susceptible to releasing their contents of free amino acids during extraction.

Often it is stated that the softness of water is important for dashi preparation [10]. This may be true for the total flavour of the extract, but we cannot discern any significant dependence on water hardness in terms of the actual amounts of free amino acids. Also, the amino acid contents and profiles did not depend on whether we used extraction temperatures of 60°C or 100°C. Hence it is not bitter amino acids that cause the bitter taste often found in a dashi which has been prepared close to boiling.

We found that sugar kelp with and without sorus did not lead to a different dashi in terms of amino acid composition. Still, it is well-known that the sorus of some seaweeds can be more flavourful than the other parts of the fronds. This is recognised particularly in the case of the brown seaweed wakame (Undaria pinnatifida), in which the reproductive organs, the sporophylls (mekabu), are appreciated for their mouth-filling flavour, which might be caused by their higher fatty acid contents compared to the fronds.

Traditional Japanese dashi recipes prescribe addition of the prepared fish product katsuobushi to the seaweed extract to provide for synergy compounds, specifically inosinate. In an attempt to find a suitable alternative to katsubushi to finish a dashi from dulse, we considered typical cured products that Scandinavians consume on a normal basis. Bacon was a delicious-sounding first thought. Pork bacon contains high levels of inosinate and glutamate [12] and would be an ideal starting point. The smokiness of the bacon, combined with the tealike dulse dashi, accounted for a surprisingly complex flavour profile. There was an obvious meatier taste, but it was very well balanced with a floral sweetness and slight mineral notes. We declared it a consummate success. We have also experimented with other sources to provide synergetic compounds for umami in Nordic dashi. Specifically, we have found that the inosinate contents in dried and salted chicken meat enhance the umami of the dulse dashi to some degree, whereas dried local mushrooms such as champignon seemingly contain too little guanylate to furnish anything interesting to pursue.

Conclusion

In a first attempt to explore the gastronomic potential of seaweeds from local waters to provide umami flavouring in the New Nordic Cuisine, we have undertaken a systematic study of a small selection of brown and red seaweeds and compared their umami flavouring amino acid contents with those of the traditional Japanese soup broth dashi prepared from the large, brown Japanese seaweed konbu.

Although there is a documented, historical tradition of using seaweeds in the diet of some of the Nordic countries, in particular Iceland and Greenland, seaweeds are practically absent in traditional and modern Nordic cuisine [41]. With the rise of the New Nordic Cuisine and the efforts to use local foodstuff ingredients for a New Nordic Diet, many of them almost forgotten, we have focused in particular on two seaweed species: the red seaweed dulse (Palmaria palmata) and the brown seaweed sugar kelp (Saccharina latissima). Both of these species are available in large amounts in the wild in Nordic waters and can be farmed under controlled conditions. The wild resources can be harvested in a sustainable fashion, and, because they grow in the cold, pristine Nordic waters, the seaweeds are very clean and suitable for human consumption.

We have investigated the gastronomical potential of these seaweed species by focusing on the flavouring potential of simple water extracts, similarly to the Japanese dashi that is the classic source of umami. Dashi owes its umami taste to the sodium salts of glutamic acid and aspartic acid, and any sweetness is predominantly due to free alanine. We have measured the concentration of these three amino acids in various extracts prepared under different well-controlled conditions, such as extraction temperature.

The main finding of the present work is that the use of well-controlled extraction techniques may release much more glutamate, aspartate and alaninate than the use of classic recipes involving cold-water soaking and subsequent heating in an open pan. Hence techniques involving extraction in a sealed plastic bag under vacuum pressure appear to have improved the extraction efficiency for free amino acids from seaweeds without compromising the flavour. Whereas the extraction temperature has a definite influence on the overall taste of the dashi, in particular the bitter notes developed at the higher temperatures, the amounts of glutamate, aspartate and alaninate appear to be little sensitive to whether the extraction temperature is 60°C or 100°C. Similarly, we could not detect any significant dependence of water hardness on the amount of released umami-flavouring free amino acids.

We believe that the findings of the present study may be of use for improving recipes for makingdashi, not least from konbu. Specifically, we found that whereas sugar kelp is a poor umami source, dulse is an excellent source with similar amounts of umami agents compared to Japanesedashi prepared from konbu in the classic way. Dashi from dulse also contains a significant amount of alaninate, which probably contributes to its mild, sweet taste.

The flavouring abilities of Nordic dulse dashi by its infusion in various dishes have been demonstrated in the case of three specific examples: ice cream with dulse infusion, fresh cheese infused with dulse and bread made from a sourdough infused with dulse. Subjective tasting experiments suggest that dulse is indeed an attractive flavouring agent and holds great promise for novel uses, not only in the New Nordic Cuisine but in general.

Materials and methods

Seaweed cultivation and harvesting

Sugar kelp (Saccharina latissima) was cultivated in the open coastal waters of Kattegat in Denmark. The sporophytes of sugar kelp are sawn on smaller ropes in a hatchery, and they attach to the rope with their holdfasts. The seeded and sprouted kelp ropes are fixed on cultivation longlines, cultivated for about 18 months and harvested when they reach a length of about 1.5 m. The controlled cultivation produces high quality with nearly no fouling. The harvested kelp is sun-dried immediately after harvest.

Dulse (Palmaria palmata) and graceful red weed (Gracilaria verrucosa) were grown in open tanks (pools) fed with seawater and by using air turbulence to move the seaweeds, to provide nutrition and to facilitate photosynthesis. The dulse grows by making new proliferations and then building new main tissues. The controlled cultivation in pools not only enables a fouling-free quality but also facilitates a highly red pigmentation and large protein content. The harvested dulse andGracilaria are sun-dried immediately after harvest.

Commercial seaweed supplies

Commercially available dried konbu was purchased in two different qualities: first-quality rausu-konbu from Sunaga village, Rausu District (Japan Fooding Ltd, London, UK) and second-qualityhidaka-konbu from Hokkaido, Japan (Wakou Corp, Shiga, Japan). Commercially available dried dulse was purchased from Íslensk hollusta ehf (Reykjavik, Iceland). The dulse is hand-harvested from wild Icelandic resources and subsequently dried.

Sous-vide water extracts from seaweeds

Two types of water were used for seaweed extracts: ordinary tap water (Copenhagen, Denmark; water hardness = 20°dH) and filtered, demineralised soft water. All extractions were based on 10 g of dry seaweed in 500 ml of water placed in a plastic bag sealed under vacuum pressure (sous-vide) at 98.5 kPa in a Komet Plus Vac 20 (KOMET Maschinenfabrik GmbH, Plochingen, Germany) and immersed over a period of 45 minutes in a water bath at the prescribed constant extraction temperature.

Sensory perception

Because the present paper is not intended to be a quantitative study of the sensory perception of umami flavour in the seaweed extracts and the dishes flavoured by the extracts, we have not used a formal panel of professional tasters but employed a subjective and qualitative measure of taste sensation by integrating statements from experimenters and colleague chefs who are very experienced in evaluating and describing taste. The subjective analysis was carried out by a minimum of five qualified chefs who are considered trained tasters. In the case of the dulse ice cream, the tasting was part of a master’s degree thesis on the complexity in food (Faculty of Life Sciences, University of Copenhagen, Copenhagen, Denmark) that was favourably received by a tasting panel of 60 persons. In addition, we registered responses from a large number of individual tasters on different occasions when the dulse-infused dishes were presented and tasted.

Amino acid analysis

All chemicals used were from Sigma-Aldrich (Copenhagen, Denmark) and of HPLC quality or better. Amino acid analysis was performed using the Biochrom 31+ Protein Hydrolysate System amino acid analyser (Biochrom, Cambridge, UK). Prior to analysis, proteins were precipitated by addition of trichloroacetic acid, and lipids were extracted with hexane. The amino acids were identified and quantified by comparison with pure amino acid standards with a major focus on glutamic acid, aspartic acid and alanine in their deprotonated states.

Abbreviations

GMP: guanosine-5′-monophosphate (guanylate); IMP: inosine-5′-monophosphate (inosinate); MSA: monosodium aspartate (aspartate); MSG: monosodium glutamate (glutamate).

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

OGM designed the study, suggested some of the pairing of ingredients for dashi production, took part in some of the dashi preparations, researched the literature on umami and composed and wrote the paper. LW designed procedures for optimal seaweed extraction to optimise umami flavour, designed the paring of ingredients for umami flavour, prepared dashi, exercised qualitative sensory evaluation of dashi and was a coinventor of dishes flavoured with dulse-baseddashi. RB designed and implemented production facilities for seaweed farming in Denmark and harvested and processed the sugar kelp, dulse and Gracilaria used in this paper. LD set up and performed the amino acid analyses and processed the data.

Acknowledgements

Dr Kumiko Ninomiya is thanked for useful correspondence regarding dashi preparations, for information on umami flavour of soup broths, and for making available to us unpublished data on glutamate content in ichiban dashi. Prof Stefan Vogel is thanked for providing access to an HPLC installation and Prof Peter Højrup for help with the amino acid analysis. Masami Suenaga of Japan Fooding Ltd is gratefully acknowledged for help in purchasing rausu-konbu. MEMPHYS was supported as a centre of excellence by the Danish National Research Foundation for the period from 2001 to 2011. Nordic Food Lab is an independent institution fuelled by finances from external funds, private companies and foundations, including NordeaFonden, as well as from government sources. This work was supported by a grant (J.nr. 3414-09-02518) from the Danish Food Industry Agency.

References

Jean Anthleme Brillat Savarin (1825)

Lactic acid bacteria (LAB) fermentation (F) plays a major part in traditional food processing technology all over the world. LAB produce lactic acid, a gentle tasting acid which can lower the pH of a food making it uninhabitable to other types of microorganisms. LAB F contributes to preservation, flavour and texture of foods. LAB is used to describe species from many genera, most commonly Lactobaccillus, Lactococcus, Leuconostoc and Streptococcus thermophillus. (de Vos, 2005).  Certain taxa of LAB are also responsible for the production of bacteriocins, chemicals that inhibit the growth of other bacteria, the example of this par excellence being nisin. Nisin and other LAB produced bacteriocins have been shown to be effective in the prevention of many pathogenic species (Ross 2002).

LAB is the type of F occurring in sauerkraut,  yogurt or kefir, cured meats, and  idli. It is also responsible for the gentle acidity of the Belgian lambic beers as well as the malolactic wines where harsh malic acids from the grape are converted into softer and more palatable lactic acid.

Importantly LAB are found naturally in dairy products and many species are able to continue life in the presence of salt meaning that salt can be used as a MO selection mechanism as it is in sauerkraut. Many high quality LAB fermentations typically found in a kitchen are made by ‘master artisans’ who work with these cultures on a daily basis. This is particularly clear with cheese and other products of the dairy industry. Scandinavia has long been a homeland for dairying. Although in early times being split into tribal groups, some of whom did, and some of whom did not milk their animals (especially reindeer), it appears that those communities which practiced milking of animals have been more successful, possibly due to their use of this very important food source. Frederik J. Simoons (1973), when tracing lactose tolerance (tolerance resulting from the production of the lactose hydrolyzing enzyme lactase) in populations found significant biological patterns which led the researcher to hypothesise that nomadic tribes in Eurasia and north Africa were among the first to practice dairying. Gary Nabhan (2004) suggests that around 10,000 BP a mutation occurred in the DNA of an isolated tribe of Northern Europeans which allowed them to take advantage of this rich source of nutrition, Nabhan goes on to suggest that within as little as 15 generations, the prevalence of this specific gene mutation could have become wide.

The success of those peoples in the Nordic countries may also be in relation to the increase in Vitamin D, which normally is produced by the human body in the presence of sunlight, but can also be gained from milk. In the Nordic winters, sunlight is very short, and so, any extra Vitamin D can be key in maintaining health. Nordic cultures were much more inclined to drink their milk soured as in the old times it not considered healthy to drink fresh milk.

“I know that in the old times they milked the cow in a jar and then they put the milk in bigger container for fermentation but used a sieve made by hay or fresh grass to get rid of insects and stuff. The grass, I think, would impart LAB into the milk, and of course, also from the cows teat and the human skin”

(Patrik Johansson, personal email exchange, 2012)

It is said that when the Romans arrived in Northern Europe they were taught to make butter by the Celts, Pliny the Elder commenting that butter was “the most delicate of foods among barbarous nations, and one which distinguishes the wealthy from the multitude at large.” (McGee, 2004) Sweden was the worlds largest butter producer from the middle-ages until 1898, when Demark took over (Johansson) and Denmark has been in the lead ever since. Below Johansson a Swedish master artisan creator of ‘virgin butter’, describes the specific qualities that make the butter key to the dining experience at Noma describes how he learned to make butter and developed the technique into the ‘unwashed’ product, ‘virgin butter’.

“My grandmother had small dairy during the 50s and 60s where she made only butter on a very small scale. She taught me how to make butter. Her method involved the traditional way of washing the butter, that is, removing as much of the buttermilk as possible by washing it with cold clean water. Washed butter has a higher fat content and keeps longer but we discovered that by washing the butter you take away flavour and also the really nice acidity present in the buttermilk (pH 4,5).  So rather than focus on the property of keeping longer we focused on the property of taste and how to maximize it. We maximize the butter aroma during the fermentation time, which usually lasts for 48 hours, but also during the churn by churning at a higher temp than what is usually considered normal in the butter industry. During the fermentation period we use a temp curve (the details are secret). The resulting butter has a more buttery taste but also a nice acidity due to more buttermilk present…

… Late one night I churned by hand and added salt before churning and decided to stop just when the first little butter grains formed. Normally I churn until the butter grains are as big as chickpeas and then I remove most of the butter-milk. When the first little butter grains form the separation between the fat and the water (butter milk) is just taking place and the process requires constant monitoring to the second. Virgin butter has a fat content of 40% as opposed to the regular butters fat content of 80 %. In virgin butter all the acidic buttermilk is present and retained I think thanks to the capillary effect. The result is a butter that is spreadable directly from the fridge with a pleasant acidic and buttery taste. It also has a unique grainy texture.”

(Patrik Johansson, personal email exchange, 2012)

Interestingly, a very old relative of Patrik recounted to him that washed butter was for the weekends as it had to look pretty, but the unwashed butter was for the weekdays and that he always preferred the unwashed one.

It is important to note that some LAB preparations can be easily made in the restaurant kitchen, giving the chef some ability to manipulate the organoleptic properties by changing variables within the process. For example LAB are also extremely important in bread making, especially when the natural levitation process of using a sourdough are involved. Bread made with natural leavening is much tastier, and this is in part, is due to the high levels of LAB in the mother dough – this will be covered in a later post.

One useful way to inoculate a ferment with LAB (e.g. fish sauce (see previous post titles ‘Umami from Salt rich Fermentation’) or cured meat (future post) is with the addition of whey, thus hastening the process of acidification due to both the presence of lactose and of LAB in the whey. Whey can be collected after making cheese, or by straining yogurt. At NFL adding a little whey proved very useful in a number of experiments. Lactic fermentation of thinly sliced root vegetables (carrot and beetroot) proved useful in making deep fried ‘crisps’, due to the LAB processing of sugars, there was considerably less caramelisation during the high temperature frying to try this, mix thinly sliced carrots with 2% Salt and a bit of whey, leave them weighted and submerged in their own juices until the sweetness has turned to a gentle lactic acidity, then dry ‘em and fry ‘em – yum.

In other dairy products, yogurt and yogurt whey are used a great deal in adding certain flavours and textures to foods. Marinating meat with yogurt has long been practiced by various societies, the recipes for yogurt and a yogurt-marinated leg of lamb is given below.

Yogurt

Better gel is obtained with skimmed milk

Heat to 90 °C and keep there for 10 minutes – again to help with gel formation

Cool to 42 °C and add around 5 % by weight of live natural yogurt

Keep at 42 °C for 6 hours

Cool to 5 °C

Use and use a little bit of this to inoculate the next batch

Yogurt Marinated Leg of Lamb with Juniper

Remove skin and fat from leg

Rub with 2% Sea Salt and 0.5% juniper powder

Leave uncovered, hung at 5°C for 6 Days

Put leg into a vacuum bag with 300ml yogurt and leave at 5°C for 2.5 Days

Cook sous vide with 60 g butter at 58 °C / 36 hours

Remove from sous vide bag, drain and pad dry

Separate the leg into its individual muscles

Rub each of these with neutral frying oil

Roast above very hot coals until golden

Rest for 15 minutes in a warm, humid place

Slice and serve with walnut sauce and bitter greens

Bibliography

De Vos, W.M. (2005) Diversity of lactic acid bacteria, in Nout, M.J.R., De Vos, W.M., Zwietering, M.H. (eds) Food Fermentation pp. 21-28, Wageningen Academic Publishers, The Netherlands.

Ross, R.P. et al (2002) Preservation and fermentation: past, present and future, International Journal of Food Microbiology 79 : 3.

Nabhan, G.P. (2004) Why some like it hot: food genes and cultural diversity Island Press, USA.

McGee, H. (2004) On food and cooking: an encyclopedia of kitchen science, history and culture, Hodder and Stoughton, UK.

Simoons, F.J. (1973) The determinants of dairying and milk use in the old world: ecological, physiological, and cultural, Ecology of Food and Nutrition 2 : 83.

About the author

My Name is Ben Reade, I’m a chef from Edinburgh, Scotland, and for the past 3.5 years I have been studying at The University of Gastronomic Sciences in Pollenzo, Italy. For my final thesis, I came to Nordic Food Lab to research many subjects where my varied interests inerlaced with those of the Lab. The research arose out of time spent at the Nordic Food Lab between 29 September and 22 December 2011. The aim is to describe NFL’s current research to both chefs and non-specialized readers, explaining and coding the creative and scientific methodologies employed during the research at NFL, exploring their application in food experimentation and innovation. Over the next month or so I will be breaking down this thesis into manageable blog-style chunks, this is chunk 13ish of around 25 I hope you find it interesting. If you want to ask me any questions directly, I’m contactable on Twitter @benreade.

The generally recognized method for making balsamic vinegar (BV) is based on a letter written in 1860 (Saccani, 1998). The most important production of balsamic vinegar happens in Modena, central north Italy. BV is characterized by high viscosity, very dark colour, high aroma and sweetness. BV has one of the highest levels of acidity in vinegar with a pH of around 2.3-2.8 (Masini & Giudici 1995). In Denmark this culture of balsamic vinegars (BV) has arrived in the last 12 years thanks to Andreas Harder  and Claus Meyers and is now starting to enter small-scale commercial production.

BV has four important production stages. (i) the grape juice must be reduced to around 1/3 of its original volume. (ii) alcoholic fermentation of sugars into ethanol by yeasts, (iii) the oxidation of ethanol into acetic acid by acetic acid bacteria (AAB)  and then (iv) the most defining feature of this style of vinegar, the aging process which, for Traditional Balsamic Vinegar (TBV) should be over 12 years. The basic process for making balsamic vinegar, starting with empty barrels is as follows.

Firstly the grape juice, which in TBV comes from, predominantly the Trebbiano grape, undergoes a reduction. This happens at atmospheric pressure[1] in an open pan. The juice is brought to the boil, at which point it is skimmed to remove foam and impurities. The must is then cooled and simmered at around 80 °C. This reduction process continues for many hours, until the darkening liquid thickens and reaches around 35-60 °Brix  (Solieri, Giudici, 2009).

In the alcoholic fermentation stage, sugars are converted into ethanol alcohol. In grape juice both fructose and glucose are available in very similar quantities. Fructose undergoes more changes during the heat treatment stage, is fermented more easily by sugar tolerant yeast species, such as Zygosaccharomyces spp. Glucose on the other hand is more stable in heat but is more easily converted into ethanol by S. cerevisiae and can be metabolized directly by some strains of AAB (Solieri et al, 2006).

The current practice is to ferment sugars to alcohol until 5-7 % by volume and then to proceed to the acetic oxidation of ethanol by AAB. Historically BV makers have thought that the alcoholic and acetic fermentations took place simultaneously. It is now generally accepted by the scientific community that both must happen separately due to the sensitivity of yeast strains to acetic acid, the vast majority of yeasts being inhibited at a concentration of 1% acetic acid. Yeasts fermenting the must are of a variety of genera, Solieri and Giudici (2005) report the dominance of genera Candida, Zygosaccharomyces, Hansensapora, Saccharomyces. The first two listed here are very efficient at fermenting fructose in a sugar rich environment, they prefer fructose and will leave all the glucose behind which can then be fermented by the other two genera (Landi et al 2005).

Acetic acid reaches a concentration of 3% to before yeast fermentation is completely inhibited. Genera of AAB commonly found are Gluconacetobacter and Acetobacter. The main problem for the AAB is the high sugar concentration of the must and the high osmotic pressure this exerts on the yeasts. The use of starter cultures that have been tested for sugar tolerance is suggested however very few or none of existent BV or TBV makes use of laboratory cultures. Therefore oxidation of ethanol into acetic acid occurs through autochthonous or naturally occurring AAB. The barrels are inoculated with a certain amount of bacteria from fresh unpasteurised vinegar used to prime the barrels as well as some which come from the wood itself. When starting a new barrel set, as well as from initial priming vinegar, barrel wood and air, it is common practice to use backslopping[2] to give preference to previously successful MO from an established chain of barrels. So each barrel is mixed with a small amount of vinegar from an analogous barrel of a parallel set that has already been up and running for some years.

To make BV, first the barrels must be selected. For TBV, the barrels should be of 50 L, 40 L, 30 L, 20 L or 15 L. These should be of a variety of different woods; we saw barrels of chestnut, oak, cherry, acacia and oak : they may also be of mulberry or juniper amongst others. To make non-traditional BV, smaller barrels can be used, which speeds up the processes of both oxidation of alcohol into acetic acid and that of extracting the flavour from the wood. There should also be a standard 225 L oak cask, which may have been previously used for winemaking – this will be used for storing must before it enters the barrel process.

Before being filled up with grape must to process into BV the barrels must be primed, or ‘deflavoured’ as it is also known. First they should be filled with water to allow the wood some time to swell up, if there are cracks then the barrels may need to have their hoops tightened or may need to be adjusted by a cooper.  Once satisfactorily watertight, the barrels should be emptied of water and primed for the F by AAB and others involved in making the BV. This is accomplished by filling all the barrels with strong unpasteurised vinegar, with acidity greater than 6 %. This should be left for 6 months. Following this, fresh, strong vinegar (above 6 % titratable acidity) should be mixed 1:1 with grape (or fruit of choice) juice reduced to one third of its original volume. This mixture should be put into the barrels and left for 6 months. The large storage barrel should also be primed for 6 months with a mix of 35 % strong live vinegar and 65 % reduced apple juice (if apple balsamic is desired).

Once the process of barrel priming has taken place, the manufacture process can begin. Each barrel should at this point have liquid removed until it is 2/3 full. At this point the yearly process starts. At the end of the year, the smallest barrel should have 1 L removed (1 L from a 2/3 full 15 L barrel is 10%), then the next barrel should be used to fill this one to 2/3 and so on until all but the largest barrel is full to the 2/3 mark. This process is known as rincalzo in Italian.

Rincalzo – freshly cooked must enters on the left, BV leaves on the right.

This largest barrel of the set is then filled from the storage cask, and then the storage barrel can be filled up with more reduced juice – so it can then slowly perform the required alcoholic fermentation (to around 7%) slowly over the coming year. This is what should be used to fill up the largest of the barrel set, again to 2/3 full during rincalzo. The process of moving the unfinished BV should be done in late winter/early spring before it starts to warm up and the bacteria go into a growth phase. This means that the vinegar is transferred after maximum sedimentation caused by winter’s cold temperatures.

This process is repeated every year for 10 years, taking only 1 L or 10 % of 2/3 of the 15 L barrel. At this point, in the 11^th year one can start removing 25 % of the final barrel (2.5 L). During the process of aging a number of chemical and physical changes take place within the vinegar. It can be said that it is the must reduction and this wood ageing process that gives BV its particular character.

The wood of the barrel acts like a semi-permeable membrane, so that a certain amount of water evaporates slowly. Due to the size of pores in the wood,  in theory no molecules larger than water, such as the alcohols, esters and other molecules can escape. They contribute to the sensory experience of the finished product and remain inside the barrel (some of these are lost, and are known as the ’angels’ share’). The tradition of leaving the small lids off the barrels, with muslin over the hole (to prevent flies entering) is now being questioned. When the barrel is left open, there is no longer the selective evaporation and much of the volatile molecules are lost to the air (Giudici et al. 2006), especially during the hot summers of Modena. Some traditionalists insist that the open, ‘lid off’ system is the best and the debate as to whether the lids should be left on or removed from the barrels lives on. Especially in the Padana Plain where the technique originates, the elevated temperatures of summer create a lot of evaporation of volatile molecules. Although acidic acid bacteria require oxygen to survive, some investigation is currently underway as to whether or not some beneficial part of the headspace is lost. One of the more noticeable effects of fermenting with the lid removed is higher reduction of water content by evaporation, so higher viscosity of the final product. As higher viscosity is associated with BV that has undergone longer aging and is seen by consumers as an indicator of quality: lowering viscosity can decrease consumer perception of product quality.  This problem of viscosity can be tackled by reducing the initial must to a higher °Brix. During the summer months, barrels should be checked for vinegar mother every two weeks. If a mother forms and is not removed, the vinegar can continue to reduce beneath the cellulose layer, leaving the mother attached to the sides of the barrel higher up, this then dries out and can grow mold. In this case the vinegar should be siphoned off from beneath the mother and the barrel cleaned thoroughly with pressurized steam.

Barrels are traditionally kept in the attic where extreme temperatures of both summer and winter take their effect. In summer the hot temperatures promote more acetic fermentation, and in winter the cold helps with clarifying through sedimentation of solid parts. So temperature variation is very important. Every four years the barrels should be cleaned to remove sediment.

At NFL, one experiment for which there is great hope, is the use of quince juice to make balsamic vinegar. More about this is found in the next section.

Experimental balsamic vinegar

While learning about balsamic vinegars we were inspired to try to make one from a different fruit, and one that identified more with the Nordic area. After experimenting with numerous juices, quince struck us as something that already had a fascinatingly multi-layered aromatic profile. We went about sourcing a set of balsamic barrels, after following the above procedure, and making various preliminary experiments with quince juice, we filled up the barrels. Of course, it will take a long time to know how successful it has been, but initial impressions are extremely promising.

Quince Balsamic

1.         Using a domestic freezer, freeze the quinces slowly

2.         Defrost the quinces, collecting any juice which forms

3.         Juice the quinces using a centrifugal juicer

4.         Squeeze the pomace to ensure maximum yield (around 55% of quince weight)

5.         Reduce at 90°C until 30°Brix

6.         Put into balsamic vinegar barrels using process explained above in Balsamic vinegar section.

Ripe and perfumed quinces (Cydonia rangiferina)

 Bibliography

Ok, rather embarrassingly, I seem to have been very bad about keeping record of all the bibliography, however, around half of the information comes from talking to our friend Andreas Harder, the other half comes from the following fantastic book, which is essential reading for anyone interested in vinegars:

Solieri, L. & Giudici, P. (eds), Vinegars of the World, pp. 41-60, Springer-Verlag Italia S.r.l. Milan, Italy

The most famous slow method of vinegar production is the old French technique, known as the Orleans method. In the Orleans method barrels are filled with wine and vinegar and fermentation is carried out slowly by the AAB, which will generally metabolise all the alcohol in a 9 % ethanol wine in 1 to 3 months. When fully acidified, the vinegar is racked off leaving around 12 L inside a 225 L barrel, which can then be filled up to around half full with fresh alcoholic ‘wine’. To make sure the AAB has enough oxygen available, holes are drilled through the ends of the barrel (then covered with muslin) and the barrel is only filled until half full, allowing the maximum surface area to be exposed to air.

Because in the Orleans method the mother of vinegar is left in the barrel for the next batch of wine, the fresh wine must be poured into the barrel very slowly. This is accomplished traditionally using a funnel and glass pipes with a ‘U’ bend at the end. This allows the vinegar maker to pour directly into the bottom of the barrel, thus leaving the floating ‘mother of vinegar’[1] and the residue on the bottom of the barrel undisturbed. It is very important that the mother is not disturbed as if it sinks to the bottom of the vinegar, the ABB within the mother will be deprived of O₂ and the mother will rot and ruin all the vinegar.

The joy of brewing vinegar in a small artisan environment is that the product does not have to be the same every time; the differences between batches should be celebrated. From year-to-year, orchard-to-orchard, tree-to-tree, fruits are different as will be the results of processing them in any way. Really no effort should be made to standardize but rather to celebrate the individuality of each crop.

Apple and pear vinegar, however high quality, tend to have little of their original fruit character. However red fruits, such as plums, cherries and blackcurrants seem to be capable of maintaining their character, and, analogous to many red wines, benefit from aging. They maintain their character and develop in time, mellowing out and becoming smoother and less ‘green’. All vinegars will benefit from an aging process in a dark and cool environment.

The strength and fermentation speed of the AAB is reliant on many things, but as a species/genera that can mutate and adapt so quickly (due to short life cycle) they become more efficient after they have been fermenting the same substrate for a longer time. They have become more adapted.

Technological Advances

The Orleans method, was then developed into a faster method, ‘submerged acidification’ which allows the AAB increased contact with oxygen and therefore permiting a faster acidification. The submerged acidification method has then been further developed by Frings Inc into the ‘Frings Acetator’. This is a relatively large piece of machinery which is only worth investing in after production reaches a certain level, it does however allow the production times of vinegar to go down to around 6 hours per batch. The acetator is formed of three tanks, the main central tank is where the second fermentation occurs, when alcohol is converted into acetic acid. The ‘Frings Acetator’ works quickly by pumping 1600 L of air per hour thorough a carbon filter and into a type of blender where it is “atomized’ into the alcohol substrate. The alcohol is acetated at 30 °C and the acetator is equipped to keep this temperature stable. Depending on the strength of the acetic acid bacteria one could expect to have the vinegar ready in a Frings machine anywhere between 20-8 hours and sometimes as low as 6 hours.

When one batch is ready, one third or more is siphoned off and this is replaced with fruit wine. This keeps the AAB culture happy with more food in the form of alcohol and allows this next batch of alcoholic liquor to be acetated. The vinegar is siphoned off when the alcoholmeter reads low enough to make the vinegar legal (ie less than 0.5% alcohol by volume).

At Meyer’s, the multifaceted food business of Claus Meyer, we were fortunate to spend some time with Andreas Harder, a vinegar maker. He was kind enough to explain many of his tricks and give us starter cultures with which to continue our own experiments. One particularly interesting strategy he explained was the problem of changing over from one fruit wine to another when acidifying with only one Frings Acetator. This is approached by always getting darker progressively so the order in which the wines pass into the acetator is apple-pear-plum-blackberry and not the other way around. When changing over the fruit 9/10ths of the 1^st vinegar are removed and the volume replaced with the new fruit. Legally the vinegar can still be called by the name of the fruit with the higher concentration, without mentioning the starter culture.

When the annual cycle is finished one must return to the first, apple wine (cider). In order to make this transfer easy a certain quantity of the last batch can be kept. Although the AAB will become dormant, due to a lack of alcohol to metabolise, the unpasteurised vinegar will continue to house this ‘sleeping’ state until the next year or the next apple brewing session.

Andreas also explained to us the measurements he must make before selling his vinegar, in order to ensure it is both legal and appealing. These are:

ð    Initial Alcohol content by volume: 6-9 % preferred

ð    Acidity by volume of starting liquid as high acidity of alcoholic culture will lead to a lower acidification.

ð    Sugar: the residual sugars are very important to predict taste.

ð    Final measurement taken is of acidity, which must by law be over 5 %. This is tested by titration using NaOH 1 M. If you put 6 ml of vinegar to titrate the number given by the burette will be exactly the concentration of the acidity in the final liquid.

Experimental Vinegars

At NFL we experimented with producing various novel vinegars. To experiment with flavours, single stage fermentation was carried out by adding alcohol directly into a juice or solution. This meant that the vinegar process could be accelerated considerably. This process, which gives a second quality product (traditional two stage alcoholic-acetic fermentation should always be carried out in the production of high quality products) proved useful in investigating which flavours should be further investigated. In order to further accelerate the process we designed the following process, using an air compressor (designed for an aquarium) to pump air through a bubbling stone into the alcoholic liquid. Using the apparatus illustrated below and with appropriate inoculation with live unpasterised vinegar, a 5 % (ethanol by volume) ‘wine’ could be fully acidified in 4-5 days. Four successful vinegar recipes are detailed in the following pages.

Mushroom vinegar

1.         Put frozen whole, washed button mushrooms into oven at 200°C

3.         Roast until dark through ‘toasting’, removing and keep liquid as it collects

5.         Fill a pressure cooker with roasted mushrooms, liquid collected, and water

6.         Pressure cook for 60 mins @ 15psi

8.         Cool and strain, squeezing the mushrooms well.

9.         For 95g of mushroom stock add 6g ethanol and 30g unpasteurised apple vinegar.

10.       Leave in a wide mouthed jar to acidify. Unfortunately it is not possible to use the bubbler system for this recipe as it creates a large amount of foam.

11.       When repeating the recipe, in step 9. Use 30 Parts of this recipe instead of apple vinegar to slowly fade out the apple.

Elderflower, elderberry, woodruff and liquorice vinegar

1.         Make a traditional dry, non-sparkling elderflower wine

2.         When they come into season add ripe elderberries and leave two weeks to macerate

3.         Strain and squeeze the berries from the liquid

4.         Add 80 g of powdered liquorice root per 1 liter water and bring to 80 °C for 1 hour. Strain and add this to the elder wine – quantity to taste

5.         Add a handful of dried Woodruff, and 1/3 by volume of suitable vinegar starter (perhaps apple the first year, and this recipe the second.

6.         Leave to acidify for 3 months in open topped jar covered with a piece of Muslin to keep flies away.

Celery vinegar

1.         Juice celery, straining through a fine sieve

2.         Add 5 parts pure alcohol and 10 parts starter vinegar to 95 parts celery juice

3.         Put the mix into the bubbler system and wait until alcohol has turned into acetic acid.

Many acetic acid bacteria (AAB) are fastidious, meaning that they can be difficult to culture in laboratory situations. For this reason, as well as the complexity, fast evolutionary rate and immense size of the group has made taxonomic classification difficult in the past. Recently however, techniques of culture independent methods, such as 16S rRNA and DNA-DNA hybridization studies as well as comparative studies of phylogenic trees, physiological and morphological characteristics are causing rapid developments in classification. (Gullo and Giudici, 2009, Giraffa and Carminati, 2008)

AAB fermentation produces acetic acid, colloquially known as vinegar. Until 1935 the Acetobacteraceae family was categorized by their ability to metabolize differing nutrients. AAB capable of oxidizing (breaking down) ethanol into acetic acid in aerobic conditions are the most ubiquitous and can be found airborne in most places. There are ten genera to be included in the family of Acetobacteraceae (AAB) They are, Acetobacter, Acidomas, Glucanacteoobacter, Glucanobacter, Granulibater, Kozakia, Frateuria, Neosaia, Saccharibacter and Swaminathania (Gullo and Giudici, 2009).

Simple European Vinegars

Classic vinegars as we know them in the West are made by a number of different methods. These can basically be divided into two groups: slow and traditional techniques where attaining a finished vinegar may take from one month to many years; innovative processes which make faster processes where vinegar may be ready from alcoholic vinegar stock in as little as six hours.

Before describing some of the commonly used methods, it is important to explain the basics of vinegar production. In sugar rich, easily fermentable fruits a two stage fermentation is employed, Firstly yeasts transform sugars within the juice into alcohol. The second stage of the process, and the first performed by AAB is the transformation of ethanol alcohol into acetic acid.

Ethanol + O₂ (arrow) Acetic Acid + Water

As the AAB requires oxygen to oxidize ethanol into acetic acid, the airlock used for alcoholic fermentation is no longer necessary and the presence of air, and oxygen contained within the air, becomes very important. AAB are facultative aerobes, meaning that they must have oxygen to thrive

Another factor to consider with AAB is that they produce acetic acid, as with most microorganisms, they are adapted to living in solutions rich in their metabolites. For this reason, AAB will proliferate much more easily if some vinegar is mixed in with the alcoholic ferment, thereby acidifying the ‘wine’. This is normally carried out using an older batch of vinegar made from the same source. If this is done with unpasteurised vinegar this is also a means by which to inoculate the ‘wine’ with the correct AAB strains.

Over the next few posts we’ll be looking at various methods to make vinegar, describing along the way a few successful experiments that you can try too.

 Bibliography

Diggs, L.J.  (1989) Vinegar, the user friendly standard text guide to appreciating, making and enjoying vinegar, iUniverse, USA.

Gullo, M. and Giudici, P. (2009) Acetic acid bacteria: taxonomy from early descriptions to molecular techniques, in Solieri, L. & Giudici, P. (eds), Vinegars of the World, pp. 41-60, Springer-Verlag Italia S.r.l. Milan, Italy.

Giraffa, G and Carminati, D. (2008) Molecular techniques in food fermentation: principles and applications, in Cocolin, L. and Ercolini, D. (eds) Molecular techniques in the microbial ecology of fermented foods, Springer Science and Business Media LCC, New York.

About the author

My Name is Ben Reade, I’m a chef from Edinburgh, Scotland, and for the past 3.5 years I have been studying at The University of Gastronomic Sciences in Pollenzo, Italy. For my final thesis, I came to Nordic Food Lab to research many subjects where my varied interests inerlaced with those of the Lab. The research arose out of time spent at the Nordic Food Lab between 29 September and 22 December 2011. The aim is to describe NFL’s current research to both chefs and non-specialized readers, explaining and coding the creative and scientific methodologies employed during the research at NFL, exploring their application in food experimentation and innovation. Over the next month or so I will be breaking down this thesis into manageable blog-style chunks, this is chunk 13ish of around 25 I hope you find it interesting. If you want to ask me any questions directly, I’m contactable on Twitter @benreade.

Glucose + O₂  (arrow)  CO₂ + H₂O + Energy

When without oxygen (anaerobic conditions) they can still (although less efficiently), produce chemical energy (ATP) but this time they produce CO₂ and alcohol as products. In alcoholic fermentation of beverages, the liquids are denied oxygen using airlock systems to ensure alcoholic fermentation. In bread, the yeasts first use up available oxygen then begins its anaerobic respiration where it produces CO₂ and ethanol, the CO₂ accounts for the bubbles in the bread and the ethanol evaporates during cooking.

Glucose  (arrow)  CO₂ + Ethanol + Energy

A certain amount of this happens in nature without intervention. Most of the skins from sugary fruits, grapes, apples, plums etc, are covered in a thin layer of wild yeasts (and other microorganisms). This means that as the fruit ripens, these yeasts will be using the available sugar. If we want to make a naturally fermented alcohol we can just leave the juices of sugar rich fruits in contact with their skins for a little while, and this small amount of contact should be enough to initiate alcoholic fermentation. The only thing to ensure if you want to use this natural fermentation method,  that once the must starts to bubble, i.e. the yeasts take hold and begin transforming the sugars, that you attach an airlock system, so that the CO₂ can escape without allowing oxygen to enter the container.

Airlocking systems which can easily be used are: (A) a classic shop bought airlock, not good for very vigourous fermentation (B) a tube leaving the top of the bottle enters into a container of water, good for vigorous fermentation (C) A balloon attached to the top of the bottle, bad for vigousous fermentation, but useful for slow fermentations, especially as the quantity of gas produced can be seen visually in the size of the balloon.

To look at this from a global perspective it is fascinating to remember that animals not only drink and enjoy alcohol, but some may even have something of a ‘culture’ of making it.

 It is evident from fossils that fruit has played a major role in primate diet for at least the last 45 million years (Dudley and Stephens, 2004). As ripe fruits commonly contain yeasts it is expected that alcohol concentrations can be high enough to make plumes of alcohol in the air, which, when detected by aroma, can lead a primate to the fruit food source. It is argued that this is a possible basis for a genetic predisposition by humans toward alcohol as a hunger stimulant and indicator of nutritional value (Dudley, 2004). Indeed around 1/3 of the enzymes found in the human liver are involved in creating energy from alcohol (McGovern, 2010). Indeed it has been shown, especially in societies with lower hygiene, that drinking alcohol provides many functions, including the killing of pathogenic microorganisms in the gut. In all alcohol consuming societies, alcohol has been known to increase relaxation and social cohesion as well as uninhibiting libido, thus causing proliferation of alcohol consuming communities.

It is a popular opinion (although certainly not a definitive one) of archaeology and other humanities that populations gave up their nomadic lifestyles to take advantage of newly emerging innovative food production systems that evolved during the Neolithic revolution. Intentional and encouraged FF may have been one of them. Taking the earlier accounts of brewing monkeys and alcohol searching frugiverous primates as a starting point, it is easy to imagine humans developing alcoholic fermentation very early on in their cultural evolution.

Fermented foods are faster to cook, saving both time and fuel, have more accessible nutrients, provide interesting tastes to otherwise monotonous grain staples and can be more microbiologically safe. In the 1950’s a debate flared amongst archaeologists over which came first in human society, bread or beer. It was even argued that man might have lived on beer alone (Braidwood, 1953). The truth of the matter is much more likely to be that the two evolved together with prototypes being much more a slurry than the clarified beer or well-kneaded bread that we know so well today. It should be noted that a primitive beer could be much more nutritious than early man’s bread (McGovern, 2010).

It is thought that wild barley (Hordeum spontaneum) and other grains were first domesticated around 10,000 BP on the ‘Hilly Flanks’[1] between the Tigris and Euphrates rivers.. This was the birth of western agriculture and also a time when a series of new food preparation techniques such as soaking, heating and spicing first appeared. During times of plenty, grains from wild or cultivated grasses, or juices from fruits that had been collected would have, in a matter of a couple of days, started to ferment on their own. This process, which would have been unpredictable at best, was slowly developed as early peoples began to work out the complex relationships between the ingredients of a mixture and the time and conditions in which it was left.

The Neolithic revolution was possibly the single most important period in the history of humanity; Neolithic peoples in the Fertile Crescent (11,000 BP); the Yangtze and Yello River Basins (9000 BP); the New Guinea Highlands (9000-6000 BP); Sub-Saharan Africa (5000-4000 BP) and Eastern USA (4000-3000 BP) and possibly other places (Diamond and Bellwood, 2003) are credited with the invention of agriculture and of many foods, which continue to be consumed as staple foods to the present  day, such as bread and beer. To start with, wet, and especially germinated grain would have started to ferment on its own, boiled grains and the juice of overripe fruits starting to bubble away  – it would not have taken long for people to realize that those which turned alcoholic could give them an exciting and desirable psychological journey as well as social and medical benefits. Successful fermentation techniques spread between neighboring communities, and were developed in terms of available resources.

In the Nordic tradition perhaps the most interesting of ancient alcoholic beverages were derived from mixes of ingredients – an archaeological approach allows us the analysis of a Bronze Age burial in Egtved, Denmark. In this grave, which dates approximately from 1400 BC, was found a coffin containing a 20-year-old girl clutching a burnt child and, interesting for our purposes, a birch-bark (Betula sp.) container. Upon close inspection analyst Bille Gram ascertained the vessel originally contained cowberries (Vaccinium vitus-idaea), wheat grains, filaments of bog myrtle (Myrica gale) and pollen from lime tree (Tilia sp), meadowsweet (Filipendula ulmaria) and white clover (Trifolium repens), indicating the presence of honey. All of these ingredients have a history of being used in alcoholic beverages: the conclusion that can be drawn is that this pot once contained a mixed alcoholic beverage, of cowberry fruit wine, wheat beer and honey mead. This practice of mixing many fermentable ingredients is typical of prototypical beverages that archaeologists have unearthed from ancient burials from around the world (McGovern, 2010). They have frequently found remnants of alcoholic beverages, which more often than not, have been made form a mixture of different ingredients. (McGovern, 2010, 144).

Mead is perhaps known as the Nordic brew of choice. Famously in the English poem Beowulf, the Danish warriors drank mead in great quantities. The drink appears numerous times in Nordic mythology (Sturluson, 1220). Mead has been developed over the years with countless variants available and text being readily available for the interested reader (for example Schramm, 2003).

One curiosity of the area is the Ancient Sami[2] culture of fermenting sap from the birch tree (Betula L.) to make a weak alcoholic beverage (approx 0.5-1% vol). The sap of the tree gives a marvelous bittersweet and floral flavour (similar but different to maple syrup) and is used in the brewing of Noma’s house beer.

Beer is well established in Nordic culture, Copenhagen being the birthplace of Carlsberg and other major breweries. A number of small, Danish artisan breweries, such as Fanoe Bryghus and Mikkeller are gaining market strength. Far from the purist influence of the German ‘Reinheitsgebot’ all sorts of extra spices and aromatics are being used, not only to increase the wealth and diversity of rich and aromatic finished beverages, but also to give expression of tradition and territory to the products (Fanoe brewery visit, 19/10/2011). In reality it can easily be argued that this is in fact a return to the origins of beer, originally a highly diverse culture of home brewing where many plants were added to the homemade brews, in the Nordic Countries; for example bog myrtle (Myrica gale) and labrador tea (Rhododendron groenlandicum) (Behre, 1999). [3]

As many people have dedicated their lives to experimenting with alcohol, most of our experiments have used alcohols, tinctures and distillates prepared by others. Which have come in diverse flavours such as tinctures made with the lichen, Iceland moss (Cetraria islandica). A typical Danish bitters, Gammel Dansk now appears on the Noma desert menu, it contains a mixture of 29 herbs and spices, and is comparable to the Italian Fernet Branca or German Jagermiester.

Bibliography

Behre, K.E. (1999) The history of beer additives in Europe – a review, Vegetation History and Archaeobotany 8: 35.

Boekout, T. and Samson, R. (2005) Fungal diversity and food, in Nout, M.J.R., De Vos, W.M., Zwietering, M.H. (eds) Food Fermentation pp. 29-44, Wageningen Academic Publishers, The Netherlands.

Braidwood, R.J. (1953) Symposium: did man once live by beer alone?, American Anthropologist New Series 55  : 515.

Diamond, J. and Bellwood, P. (2003) Farmers and their languages: the first expansions,  Science 300 :  597.

Dudley, R. (2004) Ethanol, fruit ripening, and the historical origins of human alcoholism in primate frugivory, Integrative & Comparative Biology 44: 315.

Dudley, R. and Stephens, D. (2004) The drunken monkey hypothesis, Natural History 113 : 40.

Huang, H.T. (2000) Biology and biotechnology, in Needham, J. (ed) Science and Civilisation in China: Volume 6, Biology and Biological Technology, Part 5, Fermentations and Food Science, p. 245, Cambridge University Press, Cambridge, UK.

Sturlson, S. (1220) Edda ,Translated by Faulkes, A (1995) Everyman, London

Watson, P.J. (2005) Robert John Braidwood, Proceedings of The American Philosophical Society 149: 233.

About the author

My Name is Ben Reade, I’m a chef from Edinburgh, Scotland, and for the past 3.5 years I have been studying at The University of Gastronomic Sciences in Pollenzo, Italy. For my final thesis, I came to Nordic Food Lab to research many subjects where my varied interests inerlaced with those of the Lab. The research arose out of time spent at the Nordic Food Lab between 29 September and 22 December 2011. The aim is to describe NFL’s current research to both chefs and non-specialized readers, explaining and coding the creative and scientific methodologies employed during the research at NFL, exploring their application in food experimentation and innovation. Over the next month or so I will be breaking down this thesis into manageable blog-style chunks, this is chunk 6ish of around 25 I hope you find it interesting. If you want to ask me any questions directly, I’m contactable on Twitter @benreade.

When talking of food, microorganisms have been used in a plethora of different ways and a comprehensive study of this would take many lifetimes. Microbial ecology differs drastically between locations and so fermented foods made in one place, if made with indigenous and autochtanous fermentation microorganisms are likely to taste very different to those foods made in another location: relatively short distances can have a huge effect. It is for this reason that microbial biogeography[1] offers those involved with food production a possibility to create foods which genuinely speak of the territory. Microbial cultures in food processing offer the gift of genuine expression of their geographical origin or ‘terroir’ alongside human intervention and processing technique  or ‘millieu’  better than anything else.

Over the next few posts I will introduce to fermentation as a principle and we will try to classify food fermentation and drinks into some of their major categories. There are myriad different ways to classify this huge base of human knowledge and microbial activity (eg. by ingredients, by geography or by human culture). We will try and give the most general overview using the fermenting microorganismss themselves as our defining factor. Often a food fermentation may be carried out by a number of different species, either at the same time, or in succession. With fermentations involving wild microorganisms this is almost invariably the case. The ecology of fermented foods is a hugely complex and enormous subject, worthy of many lifetimes of study, here we’ll try and break it down, into a few blog posts. Due to the extreme level of ecological complexity within the world of microorganisms, it must be remembered that the classification framework offered is exaggerated in its simplicity and that, although pure microbial cultures do occasionally exist in nature, they are rare.

In biotechnology, fermentation has been defined as an anaerobic cellular process in which organic compounds are converted into simpler molecules and chemical energy (ATP) is obtained. In colloquial language fermentation has a much broader meaning, which tends to encompass the complex of enzymatic and microorganism stimulated breakdown of macromolecules within the fermentation substrate.

Fermentation was not clearly understood, (although it was carried out in a myriad of forms, all over the world for millennia) until Louis Pasteur (1822-1895) demonstrated the direct link between viable yeast cells and alcoholic fermentation, which at the time was met with great controversy (especially by advocates of ‘equivocal generation’ the now obsolete theory on the origin of life forms). Since Pasteur the definition has been defined as the conversion of sugar by yeasts into alcohol, carbon dioxide and energy. Modern definitions have become broader – Walker (1988) defines fermentation as a “slow decomposition process of organic substances induced by microorganisms, or by complex nitrogenous substances (enzymes) of plant or animal origin” (United Nations Food and Agriculture Organization (FAO)). This is the definition adopted by the FAO – it is broad enough to include enzymatic activity, which means that examples such as salt rich fish sauces (which frequently in the earlier stages are hydrolyzed by enzymatic activity alone) can be included.

Fermentation, for the good of this text, will be broadly defined as bioprocessing using microorganisms (particularly bacteria yeasts and molds) and the chemicals they produce (particularly enzymes, acids, gasses and volatile compounds) to achieve desirable characteristics (Nout, 2005, 13).

At NFL, one major area of interest is the F of various foodstuffs especially with the aim of creating and transforming flavours which can be used to increase the “vocabulary in our culinary language” (Rene Redzepi, 2011). Microbes have been proven in both ancient and recent history to be useful in transforming food products. Microorganism’s mechanisms of food transformation are still in many ways mysterious, both to science, and by those who work with them on a daily basis – perhaps NFL’s position between science and craft puts us in an unique position to explore and innovate in this area.

Perhaps some of the information included in the following posts can be useful to home cooks, chefs and food industry professionals in creating new products which can benefit the deliciousness of the food which they produce. One premise of this research is that few master artisans who make, for example, leavened bread, really have a grasp of the metabolic pathways of the yeast which they use to make the bread rise, but this does not stop them making excellent bread. The hope is that without understanding the complex microbiology at a molecular level, but with a level of understanding of the specific conditions which can encourage one or another microorganism (i.e. nutrition and limiting factors, optimal temperature, presence or absence of O₂), it will be possible to make productive experiments within this broad field of food fermentation. This text is written in the hope that with a little more knowledge of these complex bioprocesses people, with patience and experimentation, can use a plethora of wild and cultivated MO to produce high quality traditional and novel foods.

At NFL the study of fermentation arose from a search for new flavours compatible with NNC. By using something like a kombucha mother[2] to transform a liquid; e.g. carrot juice; we are utilizing what is essentially an extremely complex bio-machinery to assemble many flavor compounds (microbial metabolites, products of macromolecule hydrolysis and chemical reactions) that are practically impossible to assemble in any other way. There is a compelling sense of locality about fermented products, an identity and flavour that, due to local MO biodiversity is singular to the place it is produced. For this reason it is felt at NFL that fermented products offer a unique possibility for gastronomic representation of local biogeography. For NFL there is also a pleasure in reworking techniques that have been used throughout history in the Nordic region for increasing of desirable characteristics and preservation of foods.

It is of vital importance to understand that fermentation is not a technique that humans have invented, it is a natural process performed by the invisible world of microorganisms which we as humans have learned, and are still learning, to manipulate. Seen from a larger perspective we are one drop in an ocean of species, living and enjoying the metabolites of microorganisms.

Many other species enjoy fermentation. Just to demonstrate that we as humans are not alone, here is one notable example: the Malaysian pen-tailed treeshrew (Ptilocercus lowii), for our purposes is a particularly interesting species for its behavior[3]. This tiny primate is a completely reliant on alcohol. Every night they can be found guzzling down the equivalent of multiple bottles of wine, in the form of alcoholically fermented nectar in the flowers of the bertam palm (Eugeissona spp.). The interesting thing is, that the bertam palm relies on the treeshrew’s penchant for alcohol for pollination, the primate unwittingly takes the pollen from one flower to the next as it carries out its nightly routine. But the inter-reliance goes further still, the yeasts fermenting the nectar sweetened water have to travel to each new flower to start their work fermenting, thereby proliferating and expanding their population. This is accomplished by traveling on the treeshew’s nose as it moves in its nightly routine, going from one alcohol source to the next. This is just one example demonstrating the highly inter-dependant and ecological role that plants, animals and MO have to each other; they need each other to exist (Weins et al, 2008).

Over time, mankind has evolved systems of preservation. Those which involve fermentative processes, may often have been fortunate accidental discoveries, where a food product mixed with a certain amount of (for example) water or salt, produced an interesting sour, alcoholic or otherwise desirable quality. Once the maker began to understand exactly what he had put in this specific mixture, they would have tried to reproduce the results, and successfully preserved food would have provoked an increase in the consumer’s health, and the culture of, for example leavened bread or primitive beer, would have spread very fast. Changing and evolving as it spread over the cultural and geographical landscape.

Humans are also entirely dependent on microbial ecology to survive. The human body is a vehicle for many more MO than it has human cells – your body has a minimum of around 10 times as many microbial cells as human cells, mostly in the large intestine of the gut. Without our intestinal micro flora we quite simply could not survive, they help us especially in digesting foods; in return we supply them with a habitat and food. Taking the endosymbiotic theory of unicellular organisms as the evolutionary starting point for all other organisms we can begin to grasp the importance of the inter-reliance between species. As is eloquently described by Margulis and Dorian Sagan in their book microcosmos,

Margulis and Dorian Sagan in Sandor Ellix Katz (2011)

 We humans have learned to exploit many microorganism for our benefit; historically this has mostly been in food production, although more recently in chemical synthesis for medicine and industry. Here it is proposed that the best way to classify the innumerable food fermentations is by the type of microorganism utilized. Therefore  we need to know how to classify the microorganism themselves. It is by these groups along side the food fermentation substrate, that we offer this coarse classification of food fermentation. Now, over the next few posts we can go on to have a look at classifying our ‘living’ foods, using some examples to illustrate each, and listing some of the NFL experiments that were carried out during this ongoing investigation. Tomorrow we start with alcohol, so get ready to fill your glasses.

 Bibliography

Boekout, T. and Samson, R. (2005) Fungal diversity and food, in Nout, M.J.R., De Vos, W.M., Zwietering, M.H. (eds) Food Fermentation pp. 29-44, Wageningen Academic Publishers, The Netherlands.

Katz, S.E. (2010) Fermentation as a co-evolutionary force, in Procedings of the Oxford Symposium on Food and Cookery ‘Cured, Fermented and Smoked Foods’ pp. 165-174, Prospect Books, UK

Nout, M.J.R. (2005) Food fermentation: an introduction, in Nout, M.J.R., De Vos, W.M., Zwietering, M.H. Food Fermentation pp.13-21, Wageningen Academic Publishers, The Netherlands.

Redzepi, R. (2011) The Science of ‘Deliciousness’ on BBC HardTalk http://news.bbc.co.uk/2/hi/programmes/hardtalk/9669147.stm Retrieved [6/1/12]

Weins, F. et al (2008) Chronic intake of fermented floral nectar by wild treeshrews,  Proceedings of the National Academy of Sciences USA 105 : 10426.

Other uses for waste yeast include the manufacture of Single Cell Proteins (SCP), a term coined in the 1960s to define microbial biomass from fermentations. SCP have been shown to be promising in filling a global protein deficit although currently most waste yeast is used as animal feed (Ugalde and Castrillo 1992). During the Second World War  most protein consumed in Germany was from yeast, and the English yeast extract, ‘Marmite’ was invented during the same challenging times to assist public health in Britain (Ugalde and Castrillo 1992).

Yeast extract production is normally carried out through the process of autolysis triggered by salt. Autolysis is the process by which a cell will consume itself using enzymes contained within the same cell. Origane et al (1993) found that addition of the fat binding chitosan (extractd from prawn shells) improved autolysis. We found that this helped not only autolysis but also caused a reduction in bitterness – presumable because many bitter compounds are capable of a type of chemical binding compatible with chitosan. Autolysis involves a freeing of enzymes within the yeasts in order to break down the yeast proteins. The protein should be hydrolysed as far as possible into individual amino acids to increase content of umami tasting compounds however, amino acids are also sweet and bitter, or a mixture, so the type of yeast used can have a large effect on the final product. To help with lysis the extract can be performed using extrogenous hydrolyzing enzymes (Sombutyanuchit et al 2001). Hyoky (1997) also found the breakdown of yeasts using extrogenous enzymes to be fruitful- we have used this technique in the creation of in the recipe supplied in this post, where we use koji as a source of hydrolyzing enzymes. However, if you don’t want to make koji, autolysis with endogenous enzymes is normally adequate for processing (Cahyanto et al, 2011).

Boonyeun (2011) found that amino acid content can be enhanced by a two stage autolysis. The first stage encourages breakdown through high enzyme protein concentration, the second, by dilution with water causes a higher concentration gradient leading to higher extraction from yeast cells. Yeast extracts may also contain 5’-GMP, a compound often found in mushrooms, which is synergistic with glutamate, increasing umami taste.

Ideal temperatures for autolysis depend on exact strains and desired results. Tangluer and Erten (2008) found that 50°C for 24 hours was ideal for autolysis. We found that a period at 50°C and a period at the raised temperature of 56°C to encourage optimize enzymatic action raised the acceptability of the extract – however, each type of yeast should be investigated individually.

To sterilize and encourage flavour enhancing Maillard reactions, the extract can be treated in a pressure cooker at 115°C for 20 mins before being reduced in volume through evaporation (Ke-de, 2006). Polymeric absorbents (especially Amberlite XAD-16 and Amberlite XAD-765) have been used to remove bitterness and yeast flavour from yeast extracts while keeping desirable components including yeast peptides, amino acids and neucleotides (Hyoky, 1997; Kerler and Winkel, 2002).

Cahyanto et al (2011) found that optimum pH of autolysis was at pH5. In commercial processing pH is adjusted with NaOH and HCl. Both of these chemicals leave traces in the final product, which, due to a desire of NFL to use natural products, was not considered optimal. Raising pH to strongly alkali is also used industrially in the debittering process. Instead of adjusting pH using Alkali NaOH, we used birch ash, rich in K₂CO₃ (a salt which forms a strongly alkali solution) The ash is also considered by many as having health promoting qualities. For acidifying the mixture afterwards, a strong vinegar was used and results were very delicious.

So, how does one actually make it, the recipe below tells you how to make it with a centrifuge (no, not a juicer, but one of the things used in hospitals for separating blood by spinning it super fast), however, we started this investigation before we had a centrifuge, and carried out most of the separation with coffee filters, a lengthy, but successful method. The recipe below also calls for the use of a koji extract. This was used in creating particularly delicious yeast extracts, but, as mentioned above, the enzymes within the yeast cells, should be enough for a fairly thorough breakdown if you want to make it without the koji extract then you should add water in the place of the extract.

 Bibliography

Boonyeun, P. et al (2011) Enhancement of amino acid production by two step autolysis of spent brewer’s yeast, Chemical Engineering Communications 198 : 1594.

Cahyanto, M.N. et al. (2011) Production of yeast extract from ethanol fermentation waste, The 12^th ASEAN Food Conference, 16 -18 June, 2011 Bangkok

Ferreira, I. M. P. L. V. O. et al (2010) Brewer’s Saccharomyces yeast biomass: characteristics and potential applications, Trends in Food Science & Technology 21 : 77.

Hyoky et al (1997) Non-bitter yeast extract, Trends in Food Science & Technology 8 : 383.

Kerler, J. and Winkel, C. (2002) The basic chemistry and process conditions underpinning reaction flavour production’, in Taylor, A.J (ed), Food Flavour Technology,  pp. 27-52, CRC Press, Sheffield, UK.

Origane, A. and Sato, T. (1993) Process for producing yeast extract, USA, Patent No 5188852.

Sombutyanuchit, P. et al (2001) Preperation of 5’-GMP-rich yeast extracts from spent brewer’s yeast, World Journal of Microbiology and Biotechnology 17 : 163.

Tanguler, H. and Erten, H. (2008) Utilization of spent brewer’s yeast for yeast extract production by autolysis: The effect of temperature, Food and Bioproducts Processing 86 : 317.

Ugalde, U.P. and Castrillo J.I. (2002) Single cell protiens from Fungi and Yeasts, Applied Mycology and Biotechnology, 2 : 123.

About the author

My Name is Ben Reade, I’m a chef from Edinburgh, Scotland, and for the past 3.5 years I have been studying at The University of Gastronomic Sciences in Pollenzo, Italy. For my final thesis, I came to Nordic Food Lab to research many subjects where my varied interests inerlaced with those of the Lab. The research arose out of time spent at the Nordic Food Lab between 29 September and 22 December 2011. The aim is to describe NFL’s current research to both chefs and non-specialized readers, explaining and coding the creative and scientific methodologies employed during the research at NFL, exploring their application in food experimentation and innovation. Over the next month or so I will be breaking down this thesis into manageable blog-style chunks, this is chunk 6ish of around 25 I hope you find it interesting. If you want to ask me any questions directly, I’m contactable on Twitter @benreade.

The history of soy sauce most probably starts with solid soy bean fermentations which were subsequently diluted with vinegar (Huang, 2000). Now the common practice is to ferment the sauce with brine, to extract amino acids from proteinous soybeans. At NFL investigation was carried out into the possibility of the creation and use of Nordic adaptations of both soy sauce and its close relative, miso.

The following (and preceding) photo of a white board covered in my scribblings, explainings the process of Chiang and Chiang yu, as it is made at NFL. the recipe uses yellow split peas (Pisum sativum) due to its high glutamic acid content and presence in traditional Nordic cuisine; and a heritage variety of black wheat, which is being grown experimentally in Denmark on a small organic farm (by the parents of NLF’s boat dwelling neighbour – keeping it local).

The preparation of Chiang yu normally occurs in 7 ‘macro’ stages.

(i)              Preparation of the soybeans, in commercial use, defatted beans are used allowing lipid parts to be processed into other products.

(ii)            Preparation of starchy substrate, which normally is wheat or barley, although at NFL experimental use of buckwheat (Fagopyrum esculentum) a pseudo-cereal with a long history in the Nordic regions proved successful.

(iii)           Preparation of the starter mold culture – usually consisting of Aspergillus oryzae  and A.soyae although variations include Monascus  strains. More information on molds in soy sauce can be found in a later post.

(iv)           Preparation of the koji, a mix of the above (i), (ii) and (iii) which are molded over a few days to create an enzyme rich, fermentable and sweet substrate.

(v)            Moromi fermentation is the longest stage in which yeast fermentation (particularly Zygosaccharomyces rouxii) lactic acid bacteria fermentation (usually many wild strains) and enzymatic breakdown of the substrate occurs in salt rich solution.

(vi)           The separation of moromi  into solid and liquid parts occurs at the end of the process, allowing collection of soy sauce and solid parts. The solid parts can be washed with brineto produce a second grade sauce or may be used like miso paste.

(vii)         The liquid should then be processed appropriately, as detailed below, to make a delicious and microbiologically (especially fungi) stable product

Detailed information on the production of fermented soy bean products can be found in numerous books and papers, especially useful are those of Stienkraus, (2004) and Keshun (2004).

Further experimentation is proposed to further develop the recipe given below. Examples of areas of possible experimentation are the addition of spices (such as anise or liquorice), which may improve the sensory properties of the product.  Other areas of investigation are experimentation with fermentation vessels, mixing technologies and hydraulic pressing of solid parts to maximize liquid extraction.

Use of various grains and pulses should be further investigated to maximize sweetness and umami taste, as well as general flavour and aroma. As this rich sauce has high gastronomic appeal (many people have tasted it informally at NFL and Noma has now started making 200 kg batches), it is thought by the author that a schematic version of the recipe, as given below (if you can decode my scribbling) is useful to industrial application of the techniques involved in soy sauce which, especially if applied to novel ingredients can be used to create new foods with high marketability.

And today’s Bibliography,

which, is amazing, but bloody expensive!

Huang, H.T. (2000) Biology and biotechnology, in Needham, J. (ed) Science and Civilisation in China: Volume 6, Biology and Biological Technology, Part 5, Fermentations and Food Science, p. 245, Cambridge University Press, Cambridge, UK.

Stienkrauss K. (2004) http://books.google.dk/books?id=hT1a1xR3n8EC&printsec=frontcover&dq=Keshun+2004+fermentation&hl=en&sa=X&ei=OJlrT7GDOfTP4QTG18SUBg&ved=0CFAQ6AEwBg#v=onepage&q&f=false

Liu, Keshun (2004) Fermented Soy Foods: An Overview, Pages 481-493 in Y.H. Hui and Friberg, Stig (eds) in Hui Y.H. et al. (eds), Handbook of Food and Beverage Fermentation Technology, pp. 552-568, CRC Press.

About the author

My Name is Ben Reade, I’m a chef from Edinburgh, Scotland, and for the past 3.5 years I have been studying at The University of Gastronomic Sciences in Pollenzo, Italy. For my final thesis, I came to Nordic Food Lab to research many subjects where my varied interests inerlaced with those of the Lab. The research arose out of time spent at the Nordic Food Lab between 29 September and 22 December 2011. The aim is to describe NFL’s current research to both chefs and non-specialized readers, explaining and coding the creative and scientific methodologies employed during the research at NFL, exploring their application in food experimentation and innovation. Over the next month or so I will be breaking down this thesis into manageable blog-style chunks, this is chunk 6ish of around 25 I hope you find it interesting. If you want to ask me any questions directly, I’m contactable on Twitter @benreade.