Songklanakarin Journal of Science and Technology (SJST) (Mar 2005)
Microbiology of traditional fermented soybean curd (Sufu)
Abstract
Microorganisms in traditional fermenting soybean curd (Sufu) were quantitated. Total microbial populations of bacteria, molds and yeasts were 1.6×101 to 4.0×105, 2.4×101 to 3.9×105 and 4.4×103 to 8.0×105 CFU/g, respectively. Aspergillus, Penicillium, Rhizopus and Bacillus were dominantly found in koji inoculum. Bacillus, Pediococcus and Saccharomyces were mainly detected throughout the fermentation process. The other microorganisms were Staphylococcus, Pichia and Debaryomyces. All isolated microorganisms were halotolerant at salt concentrations between 5 to 20%. Aspergillus, Penicillium and Bacillus could produce potential proteolytic and amylolytic enzymes, implying that these microorganisms may play significant roles in the fermentation of tofu substrate. The nutritional evaluation of fermenting Sufu had protein content between 16.09-21.91%, sugar 4.23- 9.14%, lipid 7.20- 12.76%, salt 10.06-11.26%, humidity 47.55-57.97%, ash 9.24-15.63%, fibre 0.10-0.16%, pH 4.99-5.75 and fermenting temperature at 29-31ºC. Additionally, aflatoxin B1 at the concentration of 10.8- 22.8 ppb could be detected in the fermenting Sufu by ELISA methods whereas the final product of Sufu remained 18.4 ppb. Additionally, the commercial Sufu in the markets had aflatoxin in the range of 1.5-15.2 ppb which is in the control of FDA (U.S.A.) standard that aflatoxin in food and peanut products should be less than 20 ppb.
