ETHNIC FERMENTED FOODS AND ALCOHOLIC BEVERAGES OF JAPAN

Introduction

Japan is an island nation surrounded by the sea, which is made up of 4 main big and more than 6800 small islands, located in the east of the Sea of Japan and in the west of the Pacific Ocean. The climate is predominantly temperate but varies greatly because the area lies about 3300 km north to south, from latitudes 24° and 46°N. According to the Köppen climate classification, it is classified as Dfa (cold, without dry season, warm summer) in Hokkaido, Dfb (cold, without dry season, hot summer) in northeast of Honshu, Cfa (temperate, without dry season, hot summer) in other regions except in several southern islands, and Am (tropical, monsoon) (Peel et al. 2007). The main ethnicity group is Japanese (98.5 %) including very small number of minority groups known as the indigenous Ainu, 0.5 % Koreans, 0.4 % Chinese, and 0.6 % others (The World Factbook 2015). Almost 70 % of the land is mountain area or covered with forest and agricultural land is only 12.5 %. The most important agricultural and fishery product is Japanese cultivar of paddy rice (8.6 million ton (mt)), and other important ones are vegetables (12 mt), potato (3.3 mt), fruits (3.1 mt), milk and milk products (7.3 mt), meats (3.3 mt), egg (2.5 mt), and fish and shellfish (4.3 mt) (Food Balance Sheet, MAFF 2014).

Until the end of the nineteenth century, Japanese people had not usually eaten mammal meats because of a religious practice, and then a special food culture called Washoku has been developed. The Washoku cuisine is based on a large variety of vegetables, edible wild plants, fish, and shellfish products which are the gifts from the natural feature of various climates in Japan as shown above. The Washoku was added to UNESCO’s roster of intangible cultural heritages in December 2013 with the backgrounds of traditional cultures (UNESCO 2013). The centerpieces of taste and cooking for Washoku cuisine are fermented condiments such as miso and shoyu, and fermented foods such as tsukemono, natto, and/or shiokara are additionally garnished to enhance the taste of cooked rice.

Fermentation can be considered as one of the beneficial results of long-standing efforts to preserve food materials and utilize them with minimal loss. Various fermented foods were created by taking advantage of domesticated microorganisms, which had been selected and bred for safe and suitable fermentation through ancestral wisdom and trial and error. For example, it was shown by genome analysis that Aspergillus oryzae, one of the main koji mold strains which has been used in the brewing of miso, shoyu, sake, etc., is completely lacking the ability of aflatoxin production because of multiple mutations and deletions in the ortholog of aflatoxin biosynthesis genes (Kusumoto et al. 1998, 2000; Matsushima et al. 2001), although it is a closely related species to A. flavus, an aflatoxin-producing one. On the other hand, A. oryzae is assumed to have 1.3–2 times more copies of genes for proteolytic and saccharolytic enzymes which help to bring out the taste and flavor of fermented foods than closely related Aspergillus species (Machida et al. 2005). These facts show that strains with phenotype useful for brewing had been selected in the long history of domestication. Koji molds (A. oryzae, A. sojae, A. luchuensis, and A. luchuensis mut. kawachii) were authorized as national microbes of Japan in 2006 by the Brewing Society of Japan, because they are especially important for the living and culture of the Japanese, the industries of foods and alcoholic beverages, and also the field of biotechnology in Japan (Brewing Society of Japan 2006).

Miso and shoyu are thought to derive from the cereal jiang of ancient China, which was mentioned in Zhou-li compiled around two thousand years ago and instructed in Qi-min Yao-shu, the oldest agricultural text written around 540 AD, and then have developed independently in Japan (Yoshizawa 2002). Besides sake, nare-zushi, shiokara, and gyosho were also described in the text, so recipes for archetypes of these foods and beverages are also assumed to be introduced from ancient China. But present Japanese ethnic fermented foods and beverages have been localized and evolved independently by adapting to Japanese natural features, regional food materials, and customs, and then this unique food culture has been formed. This chapter introduces comprehensive Japanese traditional fermented foods and beverages that have been supporting Japanese dietary customs as a pivotal role of Washoku taste.

Miso: Soybean Paste

Outline

Japanese soybean paste, miso in Japanese, is one of the traditional, salted fermented foods mainly made from soybeans, rice, or barley. Japanese people had been eating this food for several hundred years, as miso soup or seasonings. There are varieties of miso in Japan, according to each district. The main varieties of miso are rice miso, barley miso, and soybean miso. The key for variation is type of koji (solid fermentation culture of koji mold, A. oryzae) (Imai 2009). In case of using steamed rice for the solid-state fermentation of koji mold in manufacturing of miso (this type of koji is called rice koji), the product is called rice miso. In case of using barley koji, it is called barley miso. In addition, soybean miso is unique as it is made of koji by using soybean itself as solid fermentation substrate of A. oryzae. There are several mixed types of miso, i.e., mixture of rice miso and the barley one and mixture of the rice one and soybean miso. Sometimes the manufacturers produce miso using koji fermented with wheat, buckwheat, Japanese millet, and coix seed. Miso is also classified by characteristic of its physical property. Miso where the grain shapes of steamed soybean remain is called “tsubu-miso” (granular soybean paste). Miso after the fermented materials are ground finely is called “koshi-miso” (ground soybean paste). Miso where the grain shape of rice koji remains is called “koji-miso” (koji soybean paste).

Methods of Preparation, Mode of Consumption, Culinary, and Microorganisms

The method of preparation for rice miso is described as an example. The raw materials for manufacturing miso are soybeans cooked by steaming or boiling, rice or barley cooked by steaming, and salt. The amount of soybean used for the fermentation of miso is 120 k ton (during 2009, speculated) (Japan Federation of Miso Manufacturers Corporation 2014a). Ninety percent of them are imported from the USA, Canada, and China (ibid.). Recently, the use of soybean made in Japan increases slightly. The properties of the soybean used in miso, necessary for manufacturing miso, are large grain, thin skin, light color in the navel, high absorption of water, easy softening of the grain after steaming, light color (bright yellow) of the grain after steaming, and good fragrance after steaming. The other points are high contents of total sugar and low lipid content.

The total amount of rice used in the manufacture of miso is subject to making koji. It is not necessary for the rice to have a specific property like rice wine. The degree of polishing of rice is the same as the one for eating. The salt containing low content of iron and copper is used. The grade of the water for miso should be drinkable, and it should contain low content of iron and copper, manganese, and calcium ions. The koji starter microorganism is A. oryzae. The conidia of this fungus are delivered from companies having special technique for preparing and maintaining koji mold and its conidia. For sweet miso, the A. oryzae strain producing strong amylase activity should be selected, and the strain producing strong protease is for salty paste.

The main process contains koji making, treatment of soybeans, material mixing, fermentation and aging, and adjustment of product. Traditionally, in the manufacturer’s saying, the most important step for production of miso is koji manufacture. The second one is boiling soybeans. The third one is material mixture. Especially the quality of koji directly concerns the quality of the final product in the process of koji making (Imai 2009). The koji making contains rice treatment including polishing, rinsing, soaking, steaming, and cooling, inoculating the koji mold, fermenting the koji mold, and stopping the fermentation by adding salt which is one third of the total amount. The degree of polishing is approximately 10 %, i.e., the weight of the removed bran is 10 % of the unpolished rice. The polished rice is subject to soaking in water to let them absorb water completely.

After steaming and cooling, conidia of the koji mold are inoculated and mixed with the soaked rice. Then they are incubated at around 30 °C, which is dependent on the engineer of each company. The temperature increases up to 40 °C after some hours of inoculation due to breathing. At this point, the mycelia of the koji mold prolong and invade the inside of rice grain. If the degree of invasion is appropriate, enzyme activities necessary for miso are supposed to be enough. For the sweet and white to bright yellow type of miso, the maximum temperature should be above 35 °C to increase amylase activity. For the salty and deep-colored one, the temperature should be below 30 °C to increase protease activity. The difference of these temperature controls is partly dependent on the gene expression profile of the enzymes. Moreover, manufacturing of sweet miso needs koji mold of low condition in order to avoid deep coloration. In the history of manufacturing miso, koji making was performed with multiple sets of wooden tray called “koji buta” (koji-making tray). Nowadays the manufacturers introduce the automatic koji-making machine.

Treatment of soybeans begins with removing any dust, soil, and hull. Then sometimes soybean grains may be polished and husks are removed to display the beautiful color of miso. After rinsing, the grains are soaked in water for a certain number of hours. During soaking, pigments or its precursors (pentose polymer, etc.) are eluted from the grain. Soaked soybean grains are then steamed to denature the protein derived from soybeans, including trypsin inhibitor. After cooling down, the steamed grains are milled with a chopper machine. Then the milled soybeans, rice koji mixed with salt, additional water, and the remaining salt are mixed together. This mixture is called moromi. In many cases, the starter microorganisms such as salt-tolerant yeast (Zygosaccharomyces rouxii) and/or lactic acid bacteria (Tetragenococcus halophilus) are simultaneously added in the moromi (Imai 2009). They are packed into barrels and kept at atmospheric temperature or sometimes at the warmer condition. At the packing process, it is necessary to remove air from the moromi in order to keep an anaerobic condition. Then they are covered with a sheet such as polyethylene and pressed with stone weight on the lid. The moromi is fermented for several months to sometimes 1 year or more. This period depends on the type of each product. During late stage of fermentation, Candida versatilis and C. etchellsii are grown, and they are related to produce fragrance specific to well-fermented miso (Suezawa and Suzuki 2007).

The rice miso shares ca. 80 % among total miso in Japan and is consumed around the whole area of Japan. It is mostly used in miso soup with dashi (Japanese soup stock made from fish and/or kelp). It is also used as seasoning for cooking of fish or meat. However, interestingly, the taste is different among each district. People living in the northern and eastern part of Japan including Hokkaido, Akita, Sendai, Tokyo, and Nagano prefer dark yellow- to orange- and sometimes brown-colored miso, which tends to be salty according to the low ratio of rice koji against soybean and salt. People in the Kansai area (including Kyoto and Osaka) prefer white- to light yellow-colored miso. It is sweet according to the high ratio of rice koji. In the Tokyo area, there is a sweet type of rice miso called “edo-ama-miso.” “Edo” is the ancient name of Tokyo and “ama” means sweet taste. The color of this type is deep, dark brown, according to the soybeans steamed deeply and the high ratio of rice koji (twofold of soybean amount). “Edo-ama-miso” is used as seasoning for cooking of seafood (fish, shellfish) and meat (beef, horse, etc.). Soybean miso is produced and consumed in the middle area of Japan, that is, Chubu area, including Nagoya. The characteristic of this type is salty and astringency, rather than sweet, taste. The people living in this area prefer this miso, and they use it, for instance, as seasoning in the soup of Japanese noodles and sauce of fried breaded pork cutlet, in addition to miso soup. Barley miso is produced and consumed in the Kyushu area. It includes both the sweet type and salty type and is used mainly in miso soup.

Biochemistry, Nutritional Composition, and Functionality

Koji mold secretes several kinds of enzyme responsible for degradation of starch, protein, and lipid, i.e., amylase, protease, and lipase. Therefore, the contents of miso include amino acids, peptides, glucose and related oligosaccharide, glycerol, fatty acids, lactic acid (from lactic acid bacteria), and salt (Watanabe 2009a). There are several studies going on for the functionality of miso against human health. Some studies are based on the results of in vitro tests, and some are on the epidemiological studies. During recent 50 years, the production of miso decreases about half according to the decrease of consumption (413 k ton on 2013) (Japan Federation of Miso Manufacturers Corporation 2014b). Those functional studies of miso hopefully affect to increase the consumption of miso.

Shoyu: Soy Sauce

Outline

Shoyu (soy sauce) is a liquid seasoning made from soybeans, wheat, and salt water by brewing using fermentation technology. It is one of the basic seasonings in Japanese cuisine. Although the seasoning named “soy sauce” is widely used in ethnic cuisine of East Asian countries, its material and manufacturing method are different from each culture and country. Japanese soy sauce is known as Japan’s taste that has been exported to more than 100 countries (Japan Soy Sauce Association 2012). On the other hand, Chinese soy sauces are primarily made from soybeans, with relatively low amounts of other grains. They can be roughly split into two classes: brewed or blended. For making the brewed-type one, the teien kotai hakko method is mainly used. The method is characterized by high temperature (about 45 °C) and short-term fermentation (about 20 days) and is quite different from the Japanese soy sauce production method (Hayashi 1988).

There are five types of shoyu roughly classified by the features, “koikuchi shoyu” (common soy sauce), “usukuchi shoyu” (light-colored soy sauce), “saishikomi shoyu” (re-fermented soy sauce), “tamari shoyu” (tamari soy sauce), and “shiro shoyu” (extra-light-colored soy sauce), (Soy Sauce Information Center 2014; Ministry of Agriculture, Forestry and Fisheries, Japan 2014).

Each individual shoyu’s features is described in detail at the final section of this chapter. There are also three different types of production method. First one is “hon-jozo” (regular fermenting method), next one is “kongo-jozo” (mixed fermenting method), and last one is “kongo” (mixture method) (Ministry of Agriculture, Forestry and Fisheries 2014).

Methods of Preparation

The method of preparation of shoyu manufacturing process by hon-jozo of koikuchi shoyu, which is the most popular in Japan, is described as follows Soy Sauce Information Center 2014):

1. Material processing step: Soybeans are soaked in water and cooked over a pressure until they are swollen. After roasting, wheat is crushed. This thermal denaturation treatment is used to facilitate the decomposition of the raw materials by koji mold such as A. oryzae and A. sojae.

2. Koji-making step: The cooked soybeans and crushed wheat are mixed in similar amounts and by adding the koji mold thereto and are cultured for 3–4 days under high humidity. The resulting culture is referred to as the shoyu-koji.

3. Fermentation step: After breaking lumps of the shoyu-koji, salt water is added to the shoyu-koji and mixed, and then it is transferred to charge in the brewing tank. The shoyu-koji and salt-water mash is called moromi. While stirring according to the situation, it is matured for a few months to a year in the tank. During maturation, enzymes from shoyu-koji break down protein and starch from grains to amino acids, a low molecular peptide, and glucose, respectively. In addition, first shoyu lactic acid bacteria and then shoyu yeast are grown in the mash. The resulting organic acid such as lactic acid, ethanol, and various aromas which are essential components in the taste and fragrance of soy sauce are produced by their action.

4. Squeezing step: By a “squeeze cloth” made of durable material such as nylon, the mixture is weighted and wrapped (moromi) to separate the solid and liquid. The resulting clear liquid is referred to as “kiage-shoyu (raw soy sauce).”

5. Heat treatment and refining step: The raw soy sauce obtained in the previous step is heated in order to add with the characteristic soy sauce aroma as well as sterilize the microorganisms. The precipitation which is insolubilized by heat denaturation is allowed to settle, and the insoluble is removed by filtration to obtain a clear liquid. After component adjustment, the soy sauce is packed in containers.

Mode of Consumption and Culinary

Shoyu is used in a wide variety of food and cuisines. This includes, of course, Japanese cuisine, which was added to UNESCO’s Intangible Cultural Heritage list in 2013. In general, shoyu is used for “tsuke-kake use (dipping-sprinkling)” and “ni-taki use (boiling-cooking).” “Tsuke-kake use” means that in the menu, such as sushi, sashimi, and tofu, we directly dip or soak them in a small amount of shoyu. On the other hand, “ni-taki use” means that in the menu, such as nikujaga or nimono dish, we boil or cook meat, fish, or vegetables with shoyu. For another use, it is also widely used as “tsuyu, the base sauce for noodle or tempura (fried fish and vegetables).” These findings show that shoyu is an essential condiment for the Japanese cuisine.

Microorganisms

Microorganisms which relate to shoyu manufacture can be roughly divided into koji mold, shoyu yeast, and shoyu lactic acid bacteria (Nakadai 2006a, b, c, 2007a, b). First A. oryzae and A. sojae, which belong to Aspergillus genus and have yellow spores, are known as koji molds (Nakadai 2006a). Both the genomes of the representative strains have been decoded (Machida et al. 2005; Sato et al. 2011). Although their genome sequence resembles that of A. flavus, an aflatoxin-producing microorganism, their genome information has demonstrated that the aflatoxin synthetic pathway of koji molds is incomplete (Nakadai 2006b; Matsushima et al. 2001). We have known two types of shoyu yeast. One is Z. rouxii, called main fermentative yeast, which mainly produces ethanol and 4-hydroxy-2 (or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF) and the main soy sauce aroma (Nakadai 2006c). The others are C. versatilis and C. etchellsii, called ripening yeasts, that mildly produce various aromas like 4-ethyl guaiacol and 4-ethylphenol in the late fermentation (Nakadai 2007a). Shoyu lactic acid bacteria, although there is a diversity of catabolism of sugar, are only known as T. halophilus (Nakadai 2007b).

Functionality and health benefits (Soy Sauce Information Center 2014)

Deodorizing: Shoyu has the effect of masking odor. Shoyu arai (rinsing with soy sauce) is a Japanese food preparation technique used to neutralize the raw smell of fish and meat.

Heat cooking effect: The sugar and amino acid content in shoyu reacts with each other when heated, in what is called an amino carbonyl reaction. This creates a unique fragrance.

Bacteriostatic effect: Shoyu contains salt and organic acids that help to prevent the growth of bacteria such as E. coli bacteria and even reduce them.

Contrasting effect: By adding a little shoyu to complete a dish, the sweetness of the flavors is accentuated. We call this the “contrasting effect.”

Salty mitigation effect: Add a few drops of shoyu to anything salty, like pickles that have been pickled for too long, and the organic acids will help to soften the saltiness.

Synergistic effect: The glutamic acid in shoyu and the inosinic acid in dried bonito flakes, katsuobushi, work together to create a deep umami. We call this the “synergistic effect flavors.”

Ethnical Value and Socioeconomy

Shoyu is produced in different regions of Japan, and each region has its own preferences and history of manufacture, producing unique characteristics (Soy Sauce Information Center 2014). Koikuchi shoyu is a common soy sauce which accounts for approximately 84 % of all shoyu consumed in Japan. It is a perfectly balanced seasoning with regard to flavor, color, and aroma. Usukuchi shoyu was born in the Kansai area, and this shoyu is lighter in color. Usukuchi shoyu contains about 10 % more salt than koikuchi shoyu and is used to preserve and enhance the natural color and flavor of food. Tamari shoyu is characterized by the grist which is almost soybeans.

This soy sauce is also characterized by its thick, umami-rich flavor and distinctive aroma. Mainly manufactured in the Chubu area, it is used both in cooking and in making other products, such as rice crackers. Saishikomi shoyu is a specially produced shoyu that is produced between the San’in area and Kyushu. Using kiage-shoyu instead of the salt water, the fermentation step is the most unique step in this soy sauce. Rich in color, flavor, and aroma, this shoyu is used mainly as a table condiment. Shiro shoyu is characterized by the grist which is almost not soybeans but wheat. This shoyu is the lightest in color of all shoyu, with a distinctive aroma, mainly produced in the Hekinan district of Aichi Prefecture in the Chubu area.

Natto: Fermented Soybean

Outline

Natto is a non-salted fermented soybean, which has been produced and consumed in Japan for over a thousand years. Natto is characterized by the offensive odor of ammonia and branched short-chain fatty acids and a very viscous polymer, polyglutamate (PGA). Although natto is eaten usually with cooked rice, it is also used as an ingredient in many dishes (sushi, soup, etc.) these days. Natto inherits nutritional advantages from soybeans, and moreover B. subtilis (natto), a sole fermentative microorganism of natto, produces some functional substances (Nagai 2015). Noteworthy substances are nattokinase, which is a serine protease activating a human fibrinolytic system, and vitamin K, which is essential to bone metabolism and blood coagulation. On the other hand, oligosaccharides, which favor the growth of lactic acid bacteria in intestines, in soybeans are consumed by B. subtilis (natto) during fermentation. Instead, B. subtilis (natto) itself seems to enhance the growth. B. subtilis (natto) also inhibits the growth of some pathogenic microorganisms. Natto was a highly localized foodstuff restricted to Japan, but now natto comes to be accepted as worldwide foodstuff, maybe because of its health-promoting benefits.

Methods of Preparation, Mode of Consumption, and Culinary

Before modernization of natto fermentation, natto was produced by packing boiled soybeans in bags of rice straws. Natto bacteria, B. subtilis (natto), habit in rice straws, and the bacteria grow on the soybeans packed in rice straws for 2 or 3 days, depending on ambient temperature, and ferment them to natto. Rice straws are used as both a source of natto bacteria and packing material. At the present day, the rice straws are replaced with a clean polymer container, and a spore suspension of B. subtilis (natto) is inoculated onto boiled soybeans. The fermentation is carried out under controlled conditions. Natto is eaten with cooked rice in many cases, especially at breakfast. Natto is also used as an ingredient in sushi, soup, pizza, spaghetti, and other dishes.

Microorganisms

Natto is fermented only by Bacillus subtilis (gram-positive, spore-forming, rod-shaped, aerobic bacteria), which was formerly named as B. natto by Sawamura (Sawamura 1906).

Because typical strains of B. subtilis (e.g., a Marburg strain) cannot make natto at all, a group of natto-fermenting B. subtilis strains are often referred to as B. subtilis (natto) for industrial reasons (Nagai 2015).

Biochemistry and Nutritional Composition

Nutritional composition per 100 g of natto is as follows: energy 200 kcal, water 59.5 g, protein 16.5 g, lipid 10.0 g, carbohydrate 12.1 g, and ash 1.9 g (Ministry of Education, Culture, Sports, Science and Technology, Japan 2014). The composition is almost equal to that of boiled soybeans. A prominent increase during fermentation from boiled soybeans is observed in a content of vitamin K (from 7 to 600 μg). As the high content of vitamin K inhibits the action of warfarin, an anticoagulant, patients administered with warfarin should not take natto (Kudo 1990). The most remarkable property of natto is production of PGA. The molecule is composed of both D- and L-glutamate, which are linked between an amino group and a γ-carboxyl group. PGA is estimated to be 106 Da (Nagai et al. 1997). The genes for PGA production were cloned in E. coli and sequenced, revealing that the PGA-producing enzyme exists as a membranous enzyme complex composed of three polypeptides (Ashiuchi et al. 1999). B. subtilis (natto) produced many kinds of enzymes, in which proteases are the most important because of their contribution to the taste of natto. Moreover, it is worth noted that the enzymes decompose allergen proteins in soybeans, resulting in the reduction of the allergic risk in soy proteins (Yamanishi et al. 1995).

Functionality and Health Benefits

Besides nutritional components, natto has a wide variety of functional compounds, which are produced by B. subtilis (natto) or inhered from soybeans (Nagai 2015). And nattokinase and probiotic effects of natto are attracting more attention of consumers. From natto, a urokinase-like enzyme was discovered and named nattokinase. The enzyme is a serine protease produced by B. subtilis (natto), and the function of nattokinase might be due to activation of a human fibrinolytic system rather than to direct decomposition of fibrin in blood vessels (Sumi 1991). Many reports on antibiotic activities of natto have been published since 1931, when Salmonella was successfully cured in a patient by oral administration of natto. One candidate of the antibiotics is dipicolinic acid contained in spores of B. subtilis (natto). Natto or B. subtilis (natto) has also probiotic activities. Oligosaccharides in soybeans favor the growth of lactic acid bacteria, but the oligosaccharides are consumed during natto fermentation. Instead, B. subtilis (natto) itself functions as probiotics in intestines (Hosoi et al. 1999).

Ethnical Value and Socioeconomy

It is thought that natto was already consumed around 1000 AD when the earliest description on natto appeared in Japanese classic literature (Watanabe 2009b). There are several legends on the origin of natto: the most famous one says that boiled soybeans packed in a bag woven with rice straws turned to natto on the back of a troop horse in a civil war (1083–1087 AD) which occurred in the northern area of Japan. This might be supported by the fact that natto is consumed more in the northern area of Japan than in the southern or western areas (Kansai area or Kyushu Island), though the regionality is dissolving today. Natto-like fermented soybeans using Bacillus sp. are produced in many areas of Asia (Nagai and Tamang 2010). Though viscous polymer often was not seen on the final products in the areas, PGA-producing strains were isolated from the products, the existence of which might indicate that natto and these foods are essentially the same. In 2005, 236,000 tons of natto were produced in Japan, soybeans of which were mainly imported from the USA, Canada, and China (Watanabe 2009b). The price of one container of natto (40 g) is about 30 yen and that of natto made of domestic soybeans is higher in Japan.

Su: Vinegar

Outline

Su is a vinegar in Japanese which is composed of fermented and synthetic vinegar. In general, fermented vinegar is usually produced from cereal or fruit, while, on the other hand, synthetic vinegar is generally produced from glacial acetic acid. In Japan, cereal vinegar is mainly consumed, and rice vinegar is the main category of cereal vinegar. Rice vinegar is defined as cereal vinegar using rice more than 40 g/l. Recently “rice black vinegar” is newly divided from “rice vinegar.” Rice black vinegar is defined as rice vinegar using rice more than 180 g/l, and color of that vinegar should be changed to bark or black via fermentation and maturation. Here, we describe the rice vinegar, especially the rice black vinegar (Yanagida 1987).

Rice vinegars are usually made directly from rice and koji, molds cultured on the steamed rice, and they are produced in stainless or rarely wood tanks without mixing and aeration. Saccharification and alcoholic fermentation were usually separated from acetic acid fermentation in rice vinegar production (Entani 2001). On the other hand, Fukuyama pot vinegar is made in pot. Fukuyama pot vinegar is one of the most traditional types of rice black vinegar in Japan produced for more than 200 years in Kagoshima Prefecture in Kyushu, the southeasternmost large island in Japan. Here, saccharification, alcohol fermentation, and acetic acid fermentation are conducted in one pot (Yanagida 1990, 2001).

Methods of Preparation

Fermentation of Fukuyama pot vinegar is conducted in loosely capped pots laid on the ground of open-air fields. Here we describe the production process and the fermentation mechanism of Fukuyama pot vinegar. At first, steamed rice, rice koji, and water were put into a pot, and then floating koji, well-dried rice koji, is scattered onto that surface. Then a roughly capped pot was laid on the plane for more than 90 days without specific manipulation, and rice vinegar with brown color is completed. Alcoholic fermentation is conducted in an anaerobic environment, and acetic acid fermentation is conducted in an aerobic environment.

However, there were no additional microorganisms and specific manipulation for controlling the complex fermentation of Fukuyama pot vinegar. Rice vinegars in Japan are usually made from rice and koji, and saccharification and alcoholic fermentation processes are usually separated from acetic acid fermentation processes. On the other hand, in Fukuyama pot vinegar, saccharification, alcoholic fermentation, and acetic acid fermentation processes proceed sequentially and partly in parallel in one pot (Koizumi et al. 1987). Here, floating koji, well-dried rice koji, described above plays an important role in Fukuyama pot vinegar. Floating koji covers the surface of fermentation mixture, inhibiting the formation of pellicle by acetic acid bacteria. After alcoholic fermentation, floating koji settles out spontaneously, and pellicle of acetic acid bacteria was formed on the fermentation mixture. Therefore, the settling out of floating koji brought about the natural transition of anaerobic alcoholic fermentation to aerobic acetic acid fermentation. Therefore, spontaneous settling out of floating koji is the most important point in the particular fermentation process of Fukuyama pot vinegar (Koizumi et al. 1988).

Increase of the weight of floating koji or change of the interfacial activity of fermentation mixture or other reasons would induce the settling out of floating koji; however, the mechanism of the settling out of floating koji is unclear. This should be clarified in the future.

Mode of Consumption and Culinary

Vinegar is usually used for flavoring, controlling microorganisms, and lowering pH. Rice vinegar is usually used for seasoning the sushi rice and also used in various Japanese dishes. Fukuyama pot vinegar is usually drunk directly for health and also can be used in various Japanese dishes (Kanie 1990).

Microorganisms

A. oryzae is used for producing koji and S. cerevisiae is used for alcoholic fermentation in rice vinegar (Koizumi et al. 1988). Acetobacter aceti or A. pasteurianus are usually used for rice vinegar fermentation (Ameyama and Ohtsuka1990). In addition, lactic acid bacteria would also contribute to the rice vinegar fermentation (Entani and Masai 1985a). In Fukuyama pot vinegar, A. oryzae is also used for producing koji and S.cerevisiae also contributed to alcoholic fermentation (Furukawa and Katakura 2012; Haruta et al. 2006). In addition A. aceti or A. pasteurianus also contributed to acetic acid fermentation. There were various lactic acid bacteria, such as Lactobacillus, Lactococcus, and Pediococcus species, which are detected from the mush of Fukuyama pot vinegar, and contribution of lactic acid bacteria to lactic acid fermentation would be important for Fukuyama pot vinegar fermentation to controlling the contamination in the early phase of fermentation (Furukawa et al. 2008a, 2008b, 2013, 2014; Okazaki et al. 2010; Koizumi et al. 1996).

Biochemistry Composition

Total nitrogen content, mainly amino acid, and organic acid content, mainly lactic acid and pyroglutamic acid (Tayama 2012), of Fukuyama pot vinegar are generally higher than other rice vinegars. These characteristic properties of chemical composition would bring about the higher umami and balmy acid taste of Fukuyama pot vinegar (Koizumi et al. 1987; Entani and Masai 1985b).

Functionality and Health Benefits

It was indicated that vinegar has some health functions: inducing saliva secretion and supporting digestion, recovery from fatigue, repressing elevation of blood sugar level, and promoting calcium absorption (Tayama 2012). Rice vinegar and Fukuyama pot vinegar also have the above health functions, and Fukuyama pot vinegar would have some other health functions (ibid.).

Ethnical Value and Socioeconomy

Fukuyama pot vinegar is now produced just in Japan, but it is thought to have handed down from surrounding countries sometime between the fourth and nineteenth century (Furukawa et al. 2008b). Fukuyama pot vinegar is produced in Kyushu Island, the southeastern most large island in Japan, and there were resembling vinegars fermented in pots in the west side of Kyushu Island. Fukuyama pot vinegar is produced in small pots and this contributes to the risk distribution. Fukuyama pot vinegar production is so economic because it needs no specific manipulation in its fermentation process, and therefore, only the Fukuyama pot vinegar survived as a commercial product in Kyushu also in Japan (Higashi 1981).

Tsukemono: Fermented Vegetables

Outline

Tsukemono is pickled vegetables of Japan which includes two categories: traditional fermented vegetables and unfermented ones. Fermented vegetables with salt and seasonings were traditionally used to extend shelf life and enhance taste and flavors. Due to development of cold chain and health considerations, salt concentration becomes lower, and fermentation is omitted from the production process in most of commercially supplied tsukemono. Nevertheless, traditional fermented vegetables and homemade fermented vegetables are still consumed at the tables in Japan. In this section, the traditional fermented vegetables are described (Miyao 2002; Koizumi 2000). Most of the vegetables, even some fruits, are used for tsukemono, for example, Japanese radish (daikon), cucumber, eggplant, and Chinese cabbage (hakusai), and these are often named as seasoning materials for pickling.

One of the representative seasoning materials is a nukadoko, which is a pasty mixture of rice bran, salt, spices, and water. Vegetables pickled in nukadoko are called nuka-zuke. Fermented nukadoko contains various lactic acid bacteria which produce lactic acid, flavors, and, in some cases, antibacterial substances called bacteriocins (Irisawa et al. 2014; Kato et al. 2014; Nakayama et al. 2007; Ono et al. 2014). Several fermented products made from local vegetables specified for tsukemono are named from the name of the vegetables. During pickling process, vegetable cells are killed in the presence of salt, and self-digested cellular materials are fermented by lactic acid bacteria, resulting in good taste, flavors, and acidification to prevent the products from spoilage bacteria.

Methods of Preparation

The methods to make tsukemono vary from a simple salting to more complicated processes involving preparation of vegetables and of fermented materials such as koji, miso, and shoyu. To make nuka-zuke, vegetables are washed and directly pickled in nukadoko. Nukadoko is made from rice bran, salt (10–15 wt.% of rice bran), seasonings (dried kelp, red pepper, Japanese pepper), and water (100 wt.% of rice bran). It is important to mix the nukadoko to stabilize the microflora and to balance anaerobic fermentation by lactic acid bacteria with aerobic fermentation by yeasts. It takes more than a week to activate microbial growth and to mature the nukadoko (Ono et al. 2015).

In the case of food manufacturers, fresh vegetables are at first brined in the presence of ca. 20 wt.% of NaCl (Miyao 2002). Figure 9.14 shows takuan-zuke in a food manufacturer, for example. Fresh daikon are washed, pickled, and weighted for several months. During fermentation, daikon turns to yellow, the specific color of takuan, by chemical change of an isothiocyanate component (Matsuoka et al. 2002, 2008). Brined daikon are washed, cut, desalted to suitable salt concentration, and packed with seasonings. Other than shio-zuke, brined vegetables are desalted and pickled with various seasonings or materials such as miso, sake, lee, etc. Most products are packed in plastic bags or containers, followed by sterilization, and put on the market.

Mode of Consumption and Culinary

A set of rice, miso soup, and a small dish of tsukemono is served practically in every traditional meal with other side dishes or after drinking sake. Japanese eat rice as their staple diet. Salty tsukemono is necessary when eating cooked rice without taste and is valued for their unique flavors. Tsukemono is a kind of ready-to-eat food without cooking and is served with Japanese tea as a snack. Some fermented vegetables, such as hakusai-zuke, takuan-zuke, and sunki-zuke, are sometimes used for stir-fries.

Microorganisms

Microorganisms involved in fermented vegetables are mainly lactic acid bacteria. For example, L. brevis (Nakagawa et al. 2001; Ogihara et al. 2009; Shinagawa et al. 1996), L. namurensis (Sakamoto et al. 2011; Kato et al. 2014), L. acetotolerans (Nakayama et al. 2007; Sakamoto et al. 2011), L. sakei (Nakagawa et al. 2001; Ogihara et al. 2009; Oyaizu and Ogihara 2009), L. curvatus (Nakagawa et al. 2001; Ogihara et al. 2009; Oyaizu and Ogihara 2009; Shinagawa et al. 1996), L. collinoides (Nakagawa et al. 2001), L.fructivorans (Nakagawa et al. 2001), L. casei (Nakagawa et al. 2001), L. casei subsp. pseudoplantarum (Shinagawa et al. 1996), L. delbrueckii (Endo et al. 2008), L. fermentum (Endo et al. 2008; Nakagawa et al. 2001), L. plantarum (Endo et al. 2008; Ogihara et al. 2009; Ono et al. 2014; Shinagawa et al. 1996), L. lactis (Nakagawa et al. 2001), L. mesenteroides (Nakagawa et al. 2001; Oyaizu and Ogihara 2009; Shinagawa et al. 1996), L. carnosum (Oyaizu and Ogihara 2009), L. citreum (Nakagawa et al. 2001), Pediococcus pentosaceus (Nakagawa et al. 2001; Zhao et al. 2012), and Pediococcus damnosus (Nakagawa et al. 2001) have been reported. Further, new species, L. kisonensis sp. nov., L. otakiensis sp. nov., L. rapi sp. nov., L. sunkii sp. nov. (Watanabe et al. 2009), L. delbrueckii subsp. sunkii subsp. nov. (Kudo et al. 2012), and L. furfuricola sp. nov. (Irisawa et al. 2014) have been found in Japanese fermented vegetables. Recent metagenomic approach will provide the information of ecosystem in fermented products (Ono et al. 2014, 2015; Sakamoto et al. 2011). Depending on the seasoning materials, yeasts such as D. hansenii, S. cerevisiae, S. servazzii, and Z. rouxii are also involved in the fermentation (Kato et al. 1991; Miyao 2002; Yamagata and Fujita 1974).

Biochemistry and Nutritional Composition

Tsukemono had been eaten as vegetable source to intake vitamins and dietary fiber before fresh vegetables are available in markets year-round. As tsukemono is made from raw vegetables in the presence of salt, and nutritional components are relatively conserved. In the case of nuka-zuke, vitamins from nukadoko, including rice bran and fermented products of bacteria, are accumulated in fermented vegetables. Other nutritional compositions are depending on the vegetables and the maturing period.

Functionality and Health Benefits

Mortality due to stroke and intake of salt is highest in the Tohoku area (northern part of Honshu Island). Causal relationship between intake of salty foods including tsukemono and unhealthy effects has been pointed out (Yamada et al. 2003). On the other hand, tsukemono is one of the sources to intake nutrients from vegetables containing dietary fibers and vitamins more than original raw vegetables. Although health benefits and risks of fermented vegetable are still debatable, fermented vegetables are important elements in Washoku (Japanese cuisine) that are thought to be an exceptionally well-balanced and healthy diet. Besides nutrients from vegetables, components involved in functionality are lactic acid bacteria and their metabolites such as γ-aminobutyric acid. Lactic strains isolated from fermented vegetables have distinct properties from strains from dairy products (Nomura et al. 2006). Functionality of so-called plant-derived LAB has been examined (Takii et al. 2013; Waki et al. 2014; Suzuki et al. 2014a, b; Higashikawa et al. 2010; Zhao et al. 2012; Yamamoto et al. 2011). Depending on the activity of glutamate decarboxylase expressed from LAB, the concentration of γ-aminobutyric acid is increased in some types of fermented vegetables (Setoguchi et al. 2005; Ueno et al. 2007; Fukai and Tukada 2007; Watanabe et al. 2009).

Ethnical Value and Socioeconomy

The first historical record of tsukemono was written in the eighth century, and varieties of tsukemono were mentioned frequently in various literatures in the tenth century (Koizumi 2000). Local distinctive fermented vegetables are produced from Hokkaido (the northernmost islands) to Okinawa (the southernmost islands), with a latitude range of 46–20°N. Local specific vegetables with specific seasoning materials provide distinctive products, which characterize local food culture. One of these products, kobutakana in Unzen (Nagasaki Prefecture (Pref.)), was selected as “Precidia” of the “Ark of Taste” project. A unique salt-free fermentation in Japan (Watanabe et al. 2009; Kudo et al. 2012; Endo et al. 2008), sunki-zuke, is made from a turnip in Kiso (Nagano Pref.), which is similar to Gundruk in India (Karki and Itoh 1988). Suguki-zuke is also made from a turnip in Kyoto Pref. and is different from sunki-zuke in fermentation in the presence of salt. Washoku is characterized as the sense of the beauty of nature and of the changing seasons. Local fermented vegetables are also important elements to express the local characteristics and seasons. Salted cherry blossoms, the national flower of Japan, are served with boiled water instead of tea at a betrothal ceremony and at a wedding.

Fermented Seafoods

Outline

A variety of fermented seafoods are produced in Japan; only representative products are introduced here, but please refer to previous monographs for additional information (Fujii 1992; Fukuda et al. 2005). Japanese fermented seafoods are divided into three major types based on the fermentation procedure, namely, salted type, pickled type, and molded type. The salted fermented foods include fish sauce and salted fish, which are typically made from simply fish and salt (more than 10 %). Fermentation of these foods involves the digestion of fish materials by self-digestion and microorganisms.

The predominant microorganisms are gram-positive cocci including halophilic lactic acid bacteria. Their organoleptic features are a salty taste, preferable with a fishy odor, and strong umami quality. Pickled fermented foods are made from raw fish materials combined with carbohydrates such as cooked rice or bran. Representative products include funa-zushi, izushi, and rice bran pickles. They are typically processed by lactic acid fermentation with bacteria. They are distinctly characterized by their sour taste and flavor, occasionally resembling cheese. The shelf life and quality stabilization period are shorter than those of salted products owing to the low salt concentration (except for salted rice bran pickles). Furthermore, there are boiled, smoke-dried, and molded fish (fushi), referred to as katsuobushi, that are made from dried smoked bonito and mold starter. The mold starter functions in the digestion of lipids and dehydration. The unique aromatic flavor derived from phenolic compounds resulting from the smoking step is also a distinct characteristic of katsuobushi. The soup stock extracted from sliced katsuobushi, called dashi, is the essence of Japanese cuisine (Fujii 1992; Fukuda et al. 2005).

Fish Sauce

Fish sauce is a liquid condiment made by the long-term fermentation of fish and salt. Japanese fish sauce is made from many types of small fish including shellfish, sandfish, sardines, squid, and others. The salt concentration is approximately 20 % or more, and the fermentation period is longer than 1 year for traditional fish sauce (Fujii 1992).

The history of fish sauce production in Japan is older than that of soy sauce; it was a popular condiment until the distribution of soy sauce (Ishige and Raddle 1990). The organoleptic features of fish sauce are salty and strong umami qualities and preferably a (sometimes unique) fishy odor. To improve the fishy smell and to reduce the fermentation period, mold starter, called koji, is added to fish materials during fish sauce processing (Funatsu et al.2000). Recently, fish sauce production in Japan has increased dramatically as a measure to reduce fishing industry waste by making full use of fish materials, although the production of traditional fish sauce is decreasing. The current production volume is estimated at approximately 6100 tons per year in Japan (Funatsu 2013).

The fermentation mechanism is the digestion of fish materials using self-digestion enzymes and microorganisms, resulting in the accumulation of chemical compounds that affect taste and flavor. The accumulation of amino acids and peptides that are associated with the typical fish sauce taste results from a self-digestion enzyme secreted from fish materials (Yamashita et al. 1991). During fermentation, bacterial counts and total nitrogen, as well as amino acids and peptides, increase; hence, the pH decreases owing to lactic acid accumulation. Halophilic lactic acid bacteria, mainly T. halophilus, are dominant during fermentation in a variety of Japanese fish sauces (Fujii 1992; Dicks et al. 2009). Changes in the bacterial flora of Japanese fish sauce during fermentation have been studied previously (Fukui et al. 2012). The bacteria play an important role in the accumulation of lactic acid during fish sauce fermentation, though they have little effect on the digestion of fish materials or the production of amino acids via enzymes. The basic quality of fish sauce is stable as long as an appropriate salt concentration is used. However, the accumulation of biogenic amines, including histamine and tyramine, sometimes occurs during fish sauce production. Certain tetragenococcal strains are histamine producers (Satomi et al. 2011, 2012).

Shiokara

Salted fish, shiokara in Japanese, refers to fish that is mixed with salt and aged. A representative product is a salted squid; approximately 20,000 tons per year are produced in Japan (Ministry of Agriculture, Forestry and Fisheries 2012). A variety of fish is used in addition to squid, including the organs of skipjack tuna, sea cucumber intestines, salmon kidneys, and others. The salt concentration is approximately 10 % for traditional products, which are stored in ambient temperatures. The aging period is 10–20 days. The optimal time for consumption after aging is within several weeks without refrigeration. Recently, consumers have demanded seafood with a reduced salt concentration. Therefore, most of the salted fish sold in Japan contains only 5 % salt or less, though it is necessary to keep the products in cold or freezing conditions during distribution and storage (Fujii 1992).

For production, fish materials are digested using self-digestion enzymes, resulting in the accumulation of chemical compounds that influence the taste and flavor (Fujii et al. 1994). The accumulation of amino acids and peptides related to the typical salted fish taste is provided by the self-digestion enzymes secreted from fish materials, and squid liver is particularly important for providing proteolytic enzymes during salted squid production. Therefore, the roles of microorganisms are not significant with respect to taste, raising questions regarding whether salted fish can be considered a fermented food or not. However, Staphylococcus spp. have been isolated from salted squid, and the bacteria have been implicated in the production of the distinct salted squid smell (Fujii et al. 1994). Since this question is still not resolved, the words “aged” and “aging” will be used instead of fermentation.

Kusaya

Kusaya is a salt-dried fish made from flying fish, amberstripe scad, and mackerel scad in the Izu Islands. The unique characteristics of kusaya are attributed to the brine used in its production. This brine has been successively used for a long time, and some are said to have been used for more than 100 years, which is called kusaya gravy (Fujii 1992). Thus, various microbial metabolites have accumulated, giving the gravy unique features and flavors. Kusaya gravy is rich in nutrients for bacteria; it contains 3–8 % NaCl (depending on the manufacturer), volatile nitrogen compounds, and low oxygen concentrations (Fujii 1992; Satomi et al. 1997). The bacterial community is complex, indicating that it cannot be applied to specific fermentation uses (Satomi et al. 1997; Takahashi et al. 2002). Owing to its turbid brown color, high viscosity, offensive smell, and other such properties, there have been concerns regarding its safety from a public health standpoint. However, it was revealed that the gravy is able to suppress the growth of some pathogenic bacteria (Fujii et al. 1990). Although the fermentation mechanisms have not been elucidated, the compounds associated with the unique taste and odor of this gravy could result from bacterial metabolites of fish body exudates during the soaking procedures. Many of new bacterial species, mainly Oceanospirillaceae species, have been isolated from the gravy (Satomi and Fujii 2014).

Nare-Zushi (Fermented Sushi, Pickled Sushi, and Matured Sushi)

Nare-zushi is fermented seafood in which fish raw materials are pickled with rice or other carbohydrate materials. Common fish used to produce nare-zushi are crucian carp, mackerel, salmon, sandfish, and others (Fujii 1992). Two types of nare-zushi are produced in Japan, one with a long-term fermentation represented by funa-zushi and one with a short-term fermentation represented by izushi. Funa-zushi, which is made from crucian carp carrying eggs, is particularly famous for its use in typical pickled sushi. The traditional preparation of una-zushi is as follows: a crucian carp carrying eggs is used as a raw material, the scales and internal organs are removed, the fish is cured in saturated saline for approximately 1 year, the fish is washed with water, cooked rice is packed into the fish abdomen, and it is fermented for an additional year.

To consume the final product, the cooked rice that adheres to the fish is removed. The fish and fish eggs are edible. Other nare-zushi products such as izushi have similar features, though the fermentation period is shorter than that of funa-zushi and taste is more general. Production and consumption volumes are decreasing owing to changes in palatability and a decreasing supply of crucian carp. However, pickled sushi products made with other fish are still familiar in each district in Japan. The sour taste and flavor are distinct characteristics, and it occasionally resembles cheese.

The chemical characteristics of funa-zushi are as follows: 2–4 % salt concentration, pH 3.7–3.8, and lactate, acetate, formate, and propionate as the dominant organic acids. The shelf life and quality stabilization period are shorter than those of salted fermented seafoods owing to the low salt concentration (except for salted rice bran pickles). The predominant microorganisms are lactobacilli, streptococci, and pediococci, which are involved in lactic acid fermentation. Therefore, the fermentation mechanism is considered typical lactic acid fermentation, and rice can be utilized as the carbon source. In the curing step, which involves the soaking of fish in saturated brine, halophilic lactic acid bacteria such as T. halophilus have been isolated. Such foods have a hygiene issue related to botulism poisoning owing to the anaerobic conditions inside the tubs used during fermentation.

Nuka-Zuke

Rice bran pickles called nuka-zuke are produced by the aging of salted fish with rice bran at ambient temperatures for over 6 months (Fujii 1992). Common fish used for nuka-zuke are mackerel, sardine, herring, and others. The traditional preparation of nuka-zuke is as follows: using whole fish, the scales and internal organs are removed, the fish is cured in saturated saline for approximately 1 week, the fish is washed with water, rice bran is packed into the fish abdomen, and it is fermented in a tub for an additional 6 months, at minimum. To consume the final product, the rice bran that adheres to the fish is removed.

The salt concentration is approximately 10 %. The organoleptic features of nuka-zuke are salty and strong umami qualities and preferably a (sometimes unique) fishy odor with rice bran flavor. In some districts, nuka-zuke is used as an ingredient in soup, because it can provide the salt. Recently, nuka-zuke production has increased dramatically with the promotion of the consumption of locally produced foods in Japan. The scale of this industry is large, valued at approximately 6 million dollars in Japan.

Like fish sauce fermentation, fermentation of nuka-zuke involves the digestion of fish materials using self-digestion enzymes and microorganisms. The accumulation of amino acids and peptides related to the typical nuka-zuke taste is attributed to the self-digestion enzymes secreted from fish material and rice bran. Halophilic lactic acid bacteria, mainly T. halophilus, are the dominant bacteria during fermentation in these foods (Kosaka and Ooizumi 2012). The bacteria play an important role in production of aromatic components during fermentation, though their ability to digest fish material and produce amino acids using enzymes is not significant (Kosaka et al. 2012). The basic quality of nuka-zuke is stable as long as the salt concentration is appropriate. Furthermore, the accumulation of biogenic amines, including histamine and tyramine, sometimes occurs during nuka-zuke production. Certain tetragenococcal strains are histamine producers (Satomi et al. 2012).

Unusual raw materials are used for nuka-zuke in some regions, such as the pufferfish ovaries, called fugunoko-nuka-zuke (fermented pufferfish ovaries in rice bran). Pufferfish ovaries contain a deadly poison, tetrodotoxin, so detoxification is an important step. Therefore, the fermentation period lasts up to 4 years. The predominant bacteria are Tetragenococcus spp., similar to other rice bran pickles. Since all nuka-zuke products contain a large amount of salt (more than 10 %), the fermentation properties are similar to those of salted-type products. During fermentation, lactic acid accumulates in a tub with fish and rice bran, which can result in the proliferation of halophilic lactic acid bacteria (Kobayashi et al. 1995).

Fushi

Katsuobushi (boiled, smoke-dried, and molded skipjack tuna) is a representative fushi product made from skipjack tuna. It is an indispensable ingredient in Japanese cuisine. The history of fushi production is very old; prototypes of the products have been dated to about 1500 years ago based on an ancient document. The present form of the molded products is very similar to those that were developed about 300 years ago in Japan (Fujii 1992). Interestingly, similar fermented foods are produced in the Maldives; the origin is unclear. The product is solid, has a low moisture content (approximately 15 % or less), and is extremely hard, causing dryness with protein vitrification. In addition to bonito, mackerel and its relatives are used as raw materials. The production of fushi is currently estimated at 90,000 tons per year, of which 32,000 tons is dried bonito in Japan (Ministry of Agriculture, Forestry and Fisheries 2012). Fushi including katsuobushi is sometimes used for soup stock, rather than food; it is sliced into thin sections and the taste and aromatic components are extracted by boiling water. Soup extracted from katsuobushi, called dashi in Japanese, contains many aromatic components and a large amount of inosinic acid that enhances the taste of glutamate (Fujii 1992). Since the salt concentration is very low (<1 a="" alone="" and="" clear="" dashi="" does="" glutamate="" however="" is="" nbsp="" not="" p="" preferred="" provide="" salt="" strongly="" taste.="" taste="" umami.="" with="">
A smoking procedure is involved in processing. The unique aromatic flavor of katsuobushi is derived from phenolic compounds that result from the smoking step. A unique final step in katsuobushi processing is molding using various Aspergillus species, though dried fish without the molding step are also produced as a commercial item in Japan. The purpose of this step is to reduce the lipid and moisture contents of the products, which suppresses the risks of lipid oxidation and microbiological spoilage caused by high water activity. The strains used in the molding step are able to degrade lipids, but have no proteolytic activity. The molding step can make dashi taste more sophisticated, refined, and sharp compared with simple dried fish prepared without molding. As was mentioned above, since the materials have already been boiled, dried, and smoked before being molded, the risk of bacterial degradation is low and the fermentation is unremarkable. However, products that are treated by molding during the final processing step are regarded as fermented seafoods.

Sake: Rice Wine

Outline

The first meaning of “sake” given by many Japanese dictionaries is “a general term for alcoholic beverage.” The second is “a transparent beverage brewed from rice by a Japanese original method.” But, we use the second meaning of sake in most cases in present Japan. I think that this situation occurred because sake has continued to be a typical alcoholic beverage in Japan through many years. In other countries, they prefer the second meaning of sake. The sake of the second meaning is described in this section.

Sake is suited to be enjoyed with dishes rather than by itself. Many Japanese like to eat and drink in a Japanese tavern, “izakaya,” where they can eat various cooking including home cooking and drink various beverages including not only sake but also other alcoholic beverages and soft drinks. In contrast to a pub in England, an izakaya attaches great importance to dishes in general. This interesting form of restaurant, izakaya, is considered to be produced by the characteristic of sake. Sake is often heated before drinking because its aroma and taste change according to temperature. It is called “kan.” The Japanese have several special terms for kan, such as “hitohada-kan” (at about 35 °C; body temperature) and “atsu-kan” (at about 50 °C). “Hiya” means the room temperature. In recent Japan, persons who enjoy “hana-bie” (at about 10 °C; temperature at the cherry blossom) or “yuki-bie” (at about 5 °C; temperature on snow) are increasing. Sake has been a central player of Japanese food culture for a long time and will remain so in the future.

Technical Terms in Sake Brewing

Several technical terms are used in sake brewing, and some of them are also used in the general public of Japan because sake has been loved by the Japanese for a long time.

Method of Preparation

Sake is brewed from rice. Beer is also brewed from grains but there is a great difference in brewing processes between sake and beer. In the case of beer, alcoholic fermentation starts after saccharification finishes. In the case of sake, saccharification and alcoholic fermentation progress simultaneously. In more detail, amylases from koji convert rice starch into glucose and yeasts convert the glucose into alcohol and carbon dioxide in the same container. Therefore, the glucose concentration during brewing of sake changes more slowly than beer. “Sandan-jikomi” is the standard in sake brewing. In this method, materials are added into moto three separate times. It was developed for the purpose to keep the yeast content and not to increase undesirable bacteria.

If enzymes are active when sake is stored, a sweetness and an unpleasant smell gradually increase (Ishikawa 2002). If a kind of lactic acid bacterium, “hi-ochi-kin,” increases, sake becomes cloudy. Therefore, sake is usually heated to about 60 °C to deactivate enzymes and to pasteurize before maturing. This process is called “hi-ire.”

Some people think sake “the fresher, the better” because some recent advertisements frequently use “sibori-tate” that means fresh. But, maturing is an important process for sake as well as other alcoholic beverages. To add a calm, smooth, and mild taste to sake, it is usually stored in a tank for less than 1 year. The sake that was stored for more than 1 year is called “chouki-chozo-shu,” which has more unique aroma and taste.

Microorganisms

There is a proverb, “First koji, the second moto, and the third tsukuri.” This expresses important processes for making sake, that is, making koji is the most important, making moto the second, and making moromi the third. In making sake, controlling microbes is essential. Koji mold, A. oryzae, is used for making koji (Ishikawa 2002). The Brewing Society of Japan authorized koji mold as the national microbe of Japan in 2006 (Brewing Society of Japan 2006). A good koji has high enzyme activities, that is, a great amount of amylases and proteases are accumulated in koji. For making a good koji, toji takes extreme care to prepare the steamed rice because it is a medium of koji mold and has a considerable effect on the final koji. To control the water content of rice with an accuracy of 1 %, washing rice, soaking rice in water, and straining water from rice are precisely carried out by all the kura-bitos in accordance with toji’s cues in a traditional koji making.

In making moto, yeast, S. cerevisiae, is cultured in an acidic medium including water, koji, and lactic acid (Ishikawa 2002). Lactic acid is added to prevent the increase of undesirable microorganisms. The moto made by this method is called “sokujo-moto.” Before developing sokujo-moto, a traditional moto, “ki-moto,” was used. The method to make ki-moto needs more time and labor. By this method, however, undesirable microorganisms are skillfully removed by the action of nitrate-reducing bacteria and lactic acid bacteria. The method is reasonable from the point of the present biology. Several sakes made from ki-moto are on the market recently because they are expected to have complex aroma and taste produced by many kinds of microorganisms (National Research Institute of Brewing, Japan 2007).

Nutritional Composition

At the point of nutritional composition, sake is distinctive among alcoholic beverages. Sake contains protein and carbohydrate more than the other alcoholic beverages (Ministry of Education Culture, Sports, Science and Technology, Japan (2014) Food Composition Database). This indicates that sake has a richer taste and is closer to soup than the other alcoholic beverages.

Health Risks and Benefits

The World Health Organization indicates many risks increased by alcohol, especially heavy episodic drinking (World Health Organization 2014). The risks include health consequences for drinkers, socioeconomic consequences for drinkers, harms to other individuals, and harms to society at large. For example, harms to other individuals can be intentional, e.g., assault or homicide, or unintentional, e.g., a traffic crash, workplace accident, or scalding of a child. If alcoholic beverages including sake are appropriately drunk, however, many persons really feel some benefits such as increased appetite and relaxation and improvement of human relations. In addition, moderate drinking reduces the risk of ischemic heart disease statistically (Roerecke and Rehm 2012). It is recently reported that some components included in sake are related to control of hypertension, prevention of diabetes, skin whitening, and so on (Imayasu 1999; Imayasu and Kawato 1999a, b).

Ethnical Value and Socioeconomy

Most of the productions of alcohol beverages in Japan were recorded in comparison with other countries because of a tax on alcohol (World Health Organization 2014). In consequence, various statistical data about alcoholic beverages published by the National Tax Agency (NTA), Japan, are available and reliable. A tax on alcohol played a critical role in modernization of Japan (National Tax Agency, Japan 2014). The ratio of a tax on alcohol to the total of national taxes was higher than 30 % in fiscal year 1902. The ratio gradually decreased with industrialization and it became lower than 3 % in fiscal 2012. The amount of a tax on alcohol was 1350 billion yen, whereas those of an income tax, a corporate tax, and a tax on tobacco were, respectively, 13,993 billion yen, 9758 billion yen, and 1018 billion yen in fiscal 2012.

NTA licenses corporations for making or selling alcohol beverages. The number of licensed factories has not markedly changed after fiscal 1990. The number of licensed wholesalers has decreased constantly from fiscal 1990 to fiscal 2012. The number of licensed retailers peaked at 201,874 in fiscal 2007. The categories of stores at which Japanese buy alcohol beverages have changed drastically only in about 20 years. More than 80 % of alcohol beverages were sold by ordinary liquor stores in fiscal 1990. In this 20 years, the ratio of the volume sold by liquor stores has decreased rapidly. In contrast, supermarkets and mass retailers have expanded their powers during the same period.

Consumption

The consumption of sake shows a chronic tendency to decrease in Japan. The ratio of sake to the total alcoholic beverages was more than 70 % in fiscal 1970 but that was about 6 % in fiscal 2012 (National Tax Agency, Japan 2014). There are similar tendencies of wine in France and Italy and beer in Germany and Belgium (World Health Organization 2014). It is socioeconomically interesting that the consumption of many traditional alcohol beverages in the original countries has been decreasing in common. But, it is a serious fact for the sake industry in Japan.

To overthrow the present situation, many persons involved in sake are continuing their efforts, for example, species improvement of rice for sake; selection of excellent yeast for making sake from flowers, etc.; development of new kinds of sake such as “chouki-chozo-shu” and sparkling sake; training sommeliers for sake, “kikisake-shi”; and reducing or eliminating the trade barriers by international negotiations. The export of sake from Japan has been increasing slightly but steadily for some years (National Tax Agency, Japan 2014).

Shochu and Awamori: Spirits

Outline

Shochu is produced through continuous distillation or single distillation. Singly distilled shochu will be discussed in this section. Shochu is an alcoholic drink made from the distillation of “moromi,” the product of the fermentation of koji, and other base ingredients such as sweet potatoes or grains. Depending on the base ingredients used, the different varieties such as sweet potato shochu, barley shochu, and rice shochu are each made in Kagoshima/Miyazaki Prefectures, Oita Prefecture, and Kumamoto Prefecture, respectively. Shochu products containing 25 % alcohol are generally sold in the market. The annual consumption of shochu is 468,000 kl in 2014 (Jyokai Times 2015). Of this, sweet potato shochu comprises 208,000 kl, and barley shochu comprises 193,000 kl, which together make up 85 % of the total amount (Jyokai Times 2015). Shochu can be drunk in many ways such as straight, on the rocks, or mixed with about 50 % hot or cold water. It is generally drunk during meals. Awamori is a type of shochu that is made from the base ingredients of just black koji and water and is produced in Okinawa Prefecture. Awamori has a longer history than shochu, and each year 23,000 kl is consumed (Jyokai Times 2015). Awamori that is stored in earthenware pots for long periods of time and allowed to mature after distillation is called “kusu” and is characterized by a gorgeous vanilla aroma.

Microorganisms Involved in Shochu Production

Koji mold, a kind of Aspergillus fungus, is classified into three types depending on the color of the conidia: yellow (A. oryzae), black (A. luchuensis), and white (A. kawachii). Yellow is used in the production of sake, miso, and soy sauce; black and white are used to make shochu. Black and white are characterized by producing citric acid and acid-resistant enzymes. Yellow was used in shochu production until 1910, but because it was difficult to keep moromi at low temperatures in the southern Kyushu region (the main production region of shochu), putrefaction was common. In 1910, Gen-ichiro Kawachi succeeded in isolating the citric acid-producing black koji mold from moromi used for the production of Okinawan awamori. The use of this koji lowered the pH of the moromi, thus preventing putrefaction and increasing the yield by 20–30 % (Kagoshima prefecture sake brewers cooperative 1940). Black koji then spread to all regions of Kagoshima Prefecture by 1919. In 1918, white koji mold was isolated as a variant of black and was highly evaluated for producing shochu with a soft aroma and taste, which led most makers to use the koji after 1945. For this reason, black became unpopular for a time, but as the demand for unique sweet potato shochu grew, in the 1980s, it underwent a revival. Black koji had been long used in the production of awamori.

The pH of the primary moromi is around 3 and the fermentation temperature sometimes exceeds 35 °C. For this reason, the yeasts used in shochu must have superior acid resistance and thermostability. All yeasts used in shochu production belong to S. cerevisiae.

Base Ingredients and Processing of Ingredients

Any base ingredients may be used for the production of shochu except for the ingredients stipulated by the Liquor Tax Act (grain that has been allowed to germinate, fruits, and sugar). Rice and barley are mainly used as the koji base ingredients. The main base ingredients include a wide variety of foods such as sweet potatoes, brown sugar, rice, barely, milk, and green tea. The base ingredients of awamori are rice koji made from rice and black koji.

The Production Process of Shochu and Awamori

Authentic shochu is produced through two-step fermentation, in which the koji (primary fermentation) and base ingredients (secondary fermentation) are fermented stepwise. This production method was established in 1914 in Kagoshima and had spread to all regions of Japan by around 1940.

Koji Production

The production of shochu starts with the creation of koji. The base ingredients are mainly rice or barley. These ingredients are washed and steamed, and then koji spores are sprinkled on these base ingredients (a process called tanetsuke), which are then left to sit for about 2 days to allow the koji mold to grow. After tanetsuke is performed, the temperature of the koji is maintained at 37–38 °C for 26–28 h. During this period, the koji is grown to sufficient levels to produce enzymes necessary or the production of shochu. Then temperature is controlled to approximately 35 °C, at which the koji can produce citric acid, which is essential for the production of shochu. The koji is ready approximately 43 h after tanetsuke. The role of koji is to (1) produce acid-resistant enzymes that will break down starch, proteins, and lipids; (2) produce citric acid that will inhibit the growth of unwanted bacteria, ensuring safe fermentation; and (3) create the flavor of the shochu. The production of citric acid is particular to koji used in the making of shochu, in contrast to yellow koji (sake koji, miso koji, soy sauce koji, etc.)

Primary Fermentation Stage

Because the main production regions of shochu are located in warm areas, there is a high risk of contamination by unwanted bacteria such as acid-forming bacteria. However, because the citric acid in the koji lowers the pH of the moromi to around 3, the growth of unwanted bacteria can be inhibited. The primary fermentation uses koji and water, and then yeast is added and saccharification and fermentation occur at the same time over a 5–6-day period at about 30 °C, thus allowing the yeast to sufficiently grow to create the primary moromi. In the case of awamori production, distillation is performed after primary fermentation has continued for about 20 days.

The Secondary Fermentation Stage

Secondary fermentation is the process of adding base ingredients and water to the primary moromi. The base ingredients of sweet potatoes, brown sugar, or barley are used as the moromi for sweet potato shochu, brown sugar shochu, and barley shochu, respectively. The secondary moromi has a pH ranging from 4 to 4.5 and thus is environment suitable for the growth of unwanted bacteria, but because the yeast concentration of the moromi ranges from 4 to 8 × 107/g immediately after fermentation and the produced alcohol concentration is approximately 4 %, fermentation occurs without the contamination of unwanted bacteria. The fermentation temperature is approximately 25 °C and is not allowed to exceed 32 °C. The secondary moromi is created after 10–14 days have passed and the alcohol level ranges from 14 % to 18 %.

The Distillation Stage

After the secondary moromi has finished the fermentation process, single distillation is performed in a pot still to create unrefined alcoholic drink ranging from 36 % to 45 % alcohol. There are two types of single distillation pot still: atmospheric distillation pot stills, which are used for sweet potato and brown sugar shochu and awamori, and vacuum distillation pot stills, which are used for grain-type shochu, such as barley and rice shochu. The distillation equipment is generally made from stainless steel, but may also be made from iron, bronze, or wood.

Atmospheric Distillation: This method generally uses steam that is directly blown into the moromi. With regard to distillation time, steam is blown into the moromi for about 30 min until shochu is produced, and the amount of steam is then controlled so that the distillation process is completed about 180 min later. At the end of distillation process, the alcohol level of distilled liquid ranges from 8 % to 10 %. Part of the taste and aroma of shochu is produced through thermal reactions during the distillation process.

Vacuum Distillation: This method of distillation was introduced in the 1970s. Shochu produced through vacuum distillation is highly regarded for its softness. The moromi is distilled in a vacuum maintained at approximately 100 Torr and kept at a temperature ranging from 40 to 50 °C.

Maturation Stage

The shochu is matured in stainless steel containers, earthenware jars, or oak barrels. Immediately after the distillation process, the distilled alcohol generally has an irritating odor (gas odor) and harsh taste and is clouded by the oily components; therefore, it is necessary to eliminate the gas odor and filtrate the oily components during storage. The gas odor is mainly composed of aldehydes and sulfur compounds. The oily components are mainly composed of chemicals such as ethyl linoleate and ethyl palmitate. Sweet potato shochu is allowed to mature for 2–4 months, and other types of shochu and awamori are generally matured for 1 year or longer. After the unrefined alcohol is filtered, matured, and blended, it is generally mixed with water and sold as 25 % alcohol drinks.

The Ingredients and Flavor of Shochu and Awamori

Besides ethanol and water, authentic shochu includes other ingredients such as higher alcohols, fatty acid esters (oily components), volatile organic acids, and minerals, but these ingredients only comprise approximately 0.2 % of the total volume. However, these trace constituents have an important meaning for the production of shochu and awamori. The differences in flavor depending on the type of shochu (sweet potato shochu, brown sugar shochu, etc.) are all due to these trace constituents. The oily components soften the strong taste of the shochu, making it mild, and thus are essential in contributing to the physical taste of the shochu.

The characteristic aroma of sweet potato shochu is reported to be created through monoterpene alcohols such as linalool, α-terpineol, citronellol, and geraniol, isoeugenol, rose oxide, and β-damascenone (Ota et al. 1990; Kamiwatari et al. 2005; Takamine et al. 2011). However, very little of these ingredients are included in rice or barley shochu. Monoterpene alcohols and β-damascenone are said to possess healing effects, and these ingredients that are particular to sweet potato shochu are thought to be important for creating a relaxing feeling after an evening drink of sweet potato shochu. Mixing with hot water especially brings out the aroma, sweetness, and healing effects of sweet potato shochu. When the maturation period of awamori becomes longer, the vanilla aroma of the drink becomes stronger. This is due to the ferulic acid esterase produced from koji that liberates the ferulic acid from the cell walls of the rice during the fermentation process. During the distillation process, it is converted into 4-vinylguaiacol and then into vanillin during the maturation stage.

Drinking Shochu Increases Thrombolytic Activity

One hour after intake of five types of alcohol beverages, plasmin was separated from blood and subjected to enzyme assay. The results show that when shochu was drunk, a significant increase in fibrinolytic activity was noted.

From its specific molecular weight, substrate specificity, and immunological properties, the enzyme was thought to be urokinase-type plasminogen activator and its precursor (Sumi 2001).

Conclusion

Japanese cuisines have evolved to make eating cooked rice more enjoyable. Fermented foods play a central role in Japanese taste and have become indispensable to Japanese food culture. In these days, not only for the importance as the taste of Japan, these fermented foods also get the attention of Japanese consumers for their health-promoting functions, e.g., prevention of radiation injury, cancer, and hypertension with miso (Watanabe 2013; Watanabe et al. 2006); angiotensin I-converting enzyme inhibitory peptides in shoyu (Nakahara et al. 2010); activation of fibrinolytic system by nattokinase (Sumi 1991); alleviation of hypertension by natto (Kim et al. 2008); enhancement of NK-cell activity and improvement of bowel symptoms by so-called plant-derived LAB in tsukemono (Takii et al. 2013); promotion of intestinal absorption of calcium (Kishi et al. 1999) and reduction of body weight, body fat mass, and serum triglyceride levels (Kondo et al. 2009) by su; and so on.

The manufacturing skills required for Japanese characteristic fermented foods have been handed down, including a lot of improvements to build up the present style, from generation to generation for several hundred years or even more than a thousand years by masters in manufacture or homemakers at home. In the recent time, development of microbiology and incipient biotechnology and industry made it possible to produce various fermented foods stably in large scale. However, small numbers of consumers choose the products made by traditional small-scale manufacturers, because those of mass production tend to be less characteristic. This may be why as many as about 1500 shoyu, 1000 miso, and 1500 sake factories continue to produce their products, although the numbers are in decline.

It is expected hereafter that the fermentation process whereby microorganisms produce many desirable properties from various raw materials in traditional fermentation procedures can be elucidated in detail by the application of advanced technology such as omics analysis that can also lead to the production of a new generation of Japanese traditional fermented foods, having characteristics such as being rich in remarkable tastes and flavors, having more health-promoting functions, being adaptable to the preference of worldwide people, being adaptable to Halal certification, etc.

By Yoshiaki Kitamura, Ken-Ichi Kusumoto, Tetsuya Oguma, Toshiro Nagai, Soichi Furukawa, Chise Suzuki, Masataka Satomi, Yukio Magariyama, Kazunori Takamine and Hisanori Tamaki in "Ethnic Fermented Foods and Alcoholic Beverages of Asia", editor Jyoti Prakash Tamang, Springer India, 2016, excerpts chapter 9. Adapted and illustrated to be posted by Leopoldo Costa.

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