The Role of Microorganisms in Soy Sauce Production

Soy sauce is a salty condiment commonly used in Eastern Asia that is made from soy beans with varying amounts of wheat or no wheat at all. It is known as shoyu in Japan, chiang-yu (or -yi) in China, kecup in Indonesia, kunjang in Korea, toyo in The Philippines, and see-ieu in Thailand (Beuchat, 1985; Djien, 1982; Fukushima, 1989). It provides flavor in an otherwise bland diet, and nutritionally it provides salt (NaCl) and predigested proteins in a diet that is traditionally protein poor. It has been made for centuries on a small scale in many towns and villages in Asia, but since 1950, particularly in Japan, the manufacturing process has been studied and modernized so that its manufacture is now concentrated in large factories using modern, controlled methods of production (Sasaki & Nunomura, 1993). In Japan, soy sauce fermentation is a major food manufacturing activity. More than 1.1 million kiloliters of soy sauce was produced in 1986 by 3000 producers, and the Kikkoman Company supplied 30% of the market (Fukushima, 1989). By 1990 there were 2871 manufacturers, 5 of which produced about 50% of the total production (Sasaki & Nunomura, 1993). While modern methods are used for most of the soy sauce produced in Japan, and factory production in other Asian countries is growing, soy sauce is still produced by methods involving no modern technological inputs (Röling, Prasetyo, Timotius, Stouthamer, & van Verseveld, 1994).