Tempeh isoflavones

Before 1990 the composition of isoflavones in soy foods was thought to be largely determined by whether the food had been fermented. Fermented foods (e.g., miso and tempeh) contain the unconjugated isoflavones agycones, while non-fermented food (e.g., tofu, soy flower, and soy milk) contain the conjugated glucoside. Subsequent experiments have demonstrated that fermentation of soy decreased the isoflavone content of the food product, but increased the urinary isoflavonoid recovery, suggesting that fermentation increases availability of isoflavones in soy (Slavin et al., 1998). 

Murakami, H., Asakawa, T., Tero, J., and Matsushita, S. 1984. Antioxidant stability of tempeh and liberation of isoflavones by fermentation. Agric. Biol. Chem. 48 2971-2975. 

Isoflavones may be found in small amounts in soy-based infant formulas [10]. Isoflavones are found in whole soybeans and products including tofu, tempeh, and soy milk. Isoflavones are classified as both phytoestrogens (plant estrogens) and selective estrogen receptor modnlators. The phytoestrogenic effects of isoflavones have led to the use of soy foods and isoflavone supplements as alternatives to conventional hormone therapy. However, studies have found no long-term complications associated with isoflavones in infants fed soy-based formulas [10,17]. 

Isoflavones (2) have usually been found as small amount phytochemicals from the legumes, grains and vegetables, and their processed foods such as traditional tofu and Indonesian tempeh which is a traditional soy product originally from Indonesia [Indonesian tempeh is made by a natural culturing and controlled fermentation process that binds soybeans into a cake form of similar to a very firm vegetarian burger patty], miso, natto, soya milk, bean curds and bean sprouts. 

Nakajima, N., Nozaki, N., Ishihara, K., Ishikawa, A., and Tsuji, H. 2005. Analysis of isoflavone content in tempeh, a fermented soybean, and preparation of a new isoflavone-enriched tempeh. JBiosci Bioeng 100, 685-687. 

Isoflavones, such as genistein (see Fig. 1) and daidzein, are found in Just a few botanical families, e.g., soy. Up to 3 mg/g of genistein and daidzein and their (1 glycosides are present in soybeans. Information on isofiavone content in soy products, such as soy milk, tofu, and fermented products such as miso, soy sauce, and tempeh, is given by Coward [92] and Wang [93]. 

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