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After considering the sweet and salty aspects of Japanese cuisine in our series on taste, this issue's feature highlights the unique sour and bitter elements that enhance the dishes of Japan. Together with umami, these are the five internationally recognized facets of taste.

Sourness, or acidity, bitterness and astringency act as supporting players that may never take center stage, but nevertheless add depth and dimension to the whole. They contribute much to what is distinctive about Japanese cuisine.

Sourness (Sanmi)

Sourness is a basic taste induced when hydrogen ions react to receptors on the surface of the taste buds. It is an indispensable and daily component of the Japanese table, whether enjoyed in foods themselves or used as a flavoring or to enrich taste.

One source of sour flavor is vinegar, and one of the most commonly used types of vinegar in Japan is rice vinegar, made by first fermenting rice until it turns into sake, and then by adding acetic acid and allowing further fermentation. After one to two months, the vinegar is ready to be filtered, pasteurized and shipped. Junmaisu, (literally, pure rice vinegar), refers to vinegar made from white rice only. Genmaisu (brown rice vinegar) has the rich, deep aroma and flavor that comes from whole rice. Dark in color, it is sometimes also referred to as kurozu (black vinegar). Composed mainly of acetic acid, rice vinegar also contains various amino acids, as well as other organic acids such as citric acid. Different ingredients yield differing concentrations of these substances, in turn endowing each vinegar with individual character.

Rice vinegar is sometimes mixed with dipping sauce for sashimi, broiled fish or hot-pot dishes such as shabu-shabu. Among these sauces are nihaizu (two-flavor vinegar), made of vinegar and soy sauce, and sanbaizu (three-flavor vinegar), which also includes mirin(sweet cooking sake); kagenzu, a blend of vinegar with the above two seasonings plus dashi stock and sugar.

The food which perhaps best represents Japanese cuisine internationally is sushi. Within the Japanese characters for "sushi" is the element "sour," a reflection of the acid taste that was once commonly produced through fermentation. Narezushi (matured sushi), sabazushi (mackerel sushi) and other early forms of sushi were all made by pickling and souring rice together with fish. By contrast, modern-day sushi rice is "soured" simply by adding vinegar.

A favorite sour food among Japanese is umeboshi, or salt-pickled Japanese plums preserved with red shiso (perilla) leaves. Halfway through the pickling process, the plums and leaves are unpacked and left to dry for a few days in the sun, and this process turns them a characteristic red color. The sourness of pickled plums, a healthy food since ancient times, comes mainly from citric acid contained in the flesh of the fruit.

Bitterness (Nigami) and Astringency (Shibumi)

Because the gustatory sense of bitterness and astringency is often associated with poison, preference for bitter or astringent foods is an acquired taste, as one learns through experience to appreciate these flavors. Most such foods, therefore, are reserved for the pleasure of sophisticated adult palates.
In Japanese, expressions that refer to bitterness or astringency, such as nigami bashitta and shibui, are used to refer to the attributes of a person, or to their taste. Theses expressions indicate qualities that may not be immediately obvious, but that nevertheless possesses a subtle, mature charm, proof of the high regard accorded these two flavors within Japanese food culture.

Although bitterness and astringency may occur together, they are scientifically distinct. Bitterness is a basic taste induced when caffeine or other substances stimulate bitterness-detecting receptors on the surface of the taste buds, while astringency is actually an irregular tactile sensation caused when the membranes in the mouth pucker in reaction to agents such as catechin or tannin.

Examples of what are considered bitter delicacies in Japan include the innards of the sweetfish (ayu) and other fish that are typically broiled whole. Goya chanpuru, or stir-fried tofu with goya (bitter melon), is another bitter dish popular in home cooking, especially in Okinawa. Butterbur buds (fukinoto), the asparagus-like udo and various edible wild plants are likewise much enjoyed throughout Japan for their astringency and bitterness.

Of all these bitter foods, however, perhaps none seems so utterly Japanese as green tea. When Japanese say "Japanese tea," they almost always refer to a type of dried unfermented green tea. Green tea is rich in astringent catechin, caffeine, sweet theanine (a type of amino acid) and bitter saponin, as well as in various sugars. When the tea is drunk, bitter and astringent flavors typically emerge first, followed by a mellow, sweet aftertaste.

Healthy Aspects

Vinegar contains acids and extracts that yield a wide variety of healthful effects, from enhancing the appetite and alleviating fatigue to assisting the absorption of calcium, reducing salt intake, lowering blood pressure and even preventing cancer. Catechin likewise possesses antioxidants as well as anti-carcinogenic, anti-cholesterol, anti-bacterial and anti-cariogenic properties. Thus, for those of mature age, sour, bitter or astringent foods are recommended not only for simple enjoyment but also for maintaining health. It is easy to see why Japanese cooking, with its broad array of healthy sour and bitter foods, is drawing increasing attention worldwide.

Author's Profile

Takashi Yamamoto was born in Fukui Prefecture in 1944. He graduated from the Osaka University School of Dentistry. He taught at the Faculty of Dentistry at the university from 1972 -1991. Since April 1991 he has held a professorship at the Faculty of Human Sciences there. A specialist in brain science and the physiology of taste, Dr. Yamamoto is currently engaged in research on the mechanisms of taste and eating preferences.