Is yeast used in making soy sauce?
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Yes, yeast is used in the making of soy sauce, the dark-brown, salty liquid that was first produced in Japan to make soy beans more palatable. The old way of fermenting soy sauce is in two stages (note: not all soy sauce is made in this way): The soy beans are soaked, cooked, and mixed with roasted wheat. Then the fungus Aspergillus oryzae is added and kept aerobically active for up to forty hours. A paste forms and is put in a deep vat; the yeast Saccharomyces rouxii and lacto-bacilli are added—both preventing further growth of the A. oryzae. A month later, a liquid forms—with large concentrations of amino acids, simple sugars, and some vitamins—to produce what we call soy sauce.