Occurrence of Biogenic Amines in Soybean Food Products

Biogenic amines (BAs) are known as toxic substances and formed in foods as a result of microbial action during fermentation and storage (Shalaby, 1996; Santos, 1996). BAs could cause diseases with food poisoning symptoms such as stimulating the nerves and blood vessels in man and animals (Joosten, 1988). The most important BAs found in foods are putrescine, cadaverine, β-phenylethylamine, tyramine, spermine, histamine, spermidine, tryptamine and agmatine. BAs exist in fish, meat, egg, cheeses, vegetables, soybean, beer, wine, etc., and their products. BAs are also known as possible precursors of carcinogens, such as N-nitrosamines (Shalaby, 1996; Santos, 1996). They are frequently found in high concentrations in foods and can not be reduced by high-temperature treatment (Shalaby, 1996; Santos, 1996). BAs in food are extensively studied; a lot of information on formation and occurrence of the biogenic amines in foods is given in recent reviews (Davidek & Davidek, 1995; Halasz et al., 1994; Santos, 1996; Stratton et al., 1991; Suzzi & Gardini, 2003). There are various kinds of soy products such as soybean paste, soy sauce, soy milk and soy curd, in which biogenic amines can be analyzed. Major sources of biogenic amines in the soy foods include: fermented/non-fermented foods such as soy sauce, Miso and Tofu. Nutritionally, soybean milk, Tofu and Sufu have the same importance to people of Asia as they prefer the salt-coagulated bean curd, not only because it has the desired texture, but also because it serves as an important source of calcium (Wang & Hesseltine, 1970). BAs are formed in fermented soybean products by microorganisms during fermentation, and high levels of BAs have been reported for soy products (Chin & Koehler, 1983; Mower & Bhagavan, 1989; Nout et al., 1993; Stratton et al., 1991; Yen, 1986). As the microbial spoilage of food may be accompanied by the increased production of decarboxylases, the presence of biogenic amines might serve as a useful indicator of food spoilage. For these reasons, it is important to monitor biogenic amines levels in foods. Soy sauce, a Chinese traditional fermented condiment, is made from soybean and wheat flour. During the manufacturing process of soy sauce, soy sauce is traditionally prepared by growing the koji mold such as Aspergillus oryzae (A. oryzae) or Aspergillus sojae (A. sojae) on the raw material containing a mixture of steam-cooked defatted soybean and roasted wheat flour. Soy sauce mash obtained by mixing the finished koji with brine solution is then subjected to various periods of ageing (Whitaker, 1978). During the fermentation of soy sauce, proteins in the raw materials are hydrolyzed into small molecular weight peptides, amino acids and ammonia