Methods are needed to detect soy allergens in hydrolyzed and fermented food. Project objectives included utilizing soy-specific ELISA kits and... Show moreMethods are needed to detect soy allergens in hydrolyzed and fermented food. Project objectives included utilizing soy-specific ELISA kits and Western blot analysis to a) measure soy protein content of commercial soy sauce products; b) trace soy proteins in model soy sauces during a traditional brewing process, and c) investigate detection of soy proteins in soy protein isolate (SPI) hydrolyzed with trypsin. Twelve different soy sauce products were purchased locally. Traditionally brewed soy sauce formulated with soybeans and wheat was produced by Kikkoman in their pilot plant in Japan. Samples were obtained at the ingredient stage, after the soybeans were cooked, at the koji and moromi mash stages, and during six months of fermentation. Partially hydrolyzed SPI was prepared by treating SPI with trypsin for up to 8 h at 38 ºC. Samples were analyzed in triplicate using six soy-specific ELISA kits: 1) Neogen Veratox for Soy; 2) Ridascreen Fast Soya; 3) Elution Technologies Soy Protein; 4) Morinaga Soya; 5) AgraQuant Soy and 6) ELISA Systems Soy Protein. Western blot analysis was performed using Morinaga Soy ELISA kit antibodies. Of the 12 commercial soy sauce products, soy protein was detected in seven products at concentrations of 7.0 (1.7% CV) - 10.5 (1.8% CV) μg/g using the Elution Technologies kit, and in five samples at concentrations of 0.31 (0.6% CV) - 1.5 (0.3% CV) μg/g with the Morinaga kit. Qualitative Western blot analysis suggested the presence of beta-conglycinin in five commercial brands. Tracking soy proteins in model soy sauce by ELISA resulted >90% decrease in detection after cooking. After addition of koji culture and brine to form the moromi mash, soy protein levels were further reduced. The measured level of soy protein after one month of fermentation was 0.67 μg/g (1.1% CV) and decreased below the limit of quantitation (LOQ, 0.31 μg/g) for samples aged 2-6 months using the Morinaga assay, while other kits resulted in soy protein concentrations below the LOQ. Western blot results showed light bands of proteins for samples after 1-2 months of fermentation suggesting the presence of beta-conglycinin. Trypsin hydrolysis of SPI resulted in a gradual decrease in soy protein bands in SDS-PAGE analysis, while some ELISA kits indicated no changes in detectability of soy proteins after 10 min of hydrolysis. Overall, the results of this study indicate that heating, hydrolysis and fermentation processes can have substantial effects on the detection of soy proteins in food. M.S. in Food Safety and Technology, December 2016 Show less