Abstract:
Soybean seeds are seeds of legume that have been historically an important source of oil and
proteins. The consumption of soybeans is elevating rapidly for its high benefits as soy meals
and its sub-products. Although, limited numbers of countries produce soybeans, however the
respective oil, meals and products are available in almost all countries of the world and they
are widely traded. Fermentation is the method used commonly to produce various soy
products; different fermentation methods are applied for different products. Various
microorganisms were involved in different types of fermented soy products; the
predominantly used strains are B. subtillis and Aspergillus. It’s proven that fermentation can
improve the physicochemical and sensory quality of the soy products. Soy consumption has
been associated with many potential health benefits in reducing chronic diseases such as
obesity, cardiovascular disease, insulin-resistance/type II diabetes, certain type of cancers,
and immune disorders. Although soybean has been widely used as a functional food, the
molecular mechanisms for its multiple functions remain unclear. The aim of this project is to
determine whether fermentation will improve the quality of soybean products in terms of
increasing digestibility, enhanced nutrition and increase the antioxidative activity, leading to
enhanced health benefits. Commercial one non-fermented soybean product; Tofu, as well as
two fungal fermented soybean products; Sufu and Douchi, in comparison with raw soybeans
were tested. Glutamic acid was the most abundant amino acid with the percentages 20.3,
19.4, 22.1 and 20.7 of total amino acids contents of soybeans, Tofu, Sufu and Douchi,
respectively. Fermentation reduced the Arginine content, where Sufu and Douchi had the
lowest values (3.4 and 4.7%) as compared to 8.6% in soybeans and Tofu. The main
component of the protein extracts of fermented soybean products; Sufu and Douchi, were
peptides with a molecular weight below 10 kDa. SDS-PAGE patterns of both soybeans and
Tofu were similar. All the samples exhibited antioxidative activity with different levels. It
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was estimated that, samples with high antioxidative activity contained a large amount of
small peptides. The antioxidative activity could ascribe to the peptides derived from soybean
proteins during the fermentation process. Extracts of fermented soybean products exhibited
selective cytotoxic activity towards Ehrlich Ascites Tumor (EAC) cells in a concentration-
dependent manner.