Enhancing selenium and key flavor compounds contents in soy sauce using selenium-enriched soybean

Selenium (Se) deficiency has become a global health threat. Se-enriched soybean was utilized to develop a Se-enriched soy sauce (SeSS), and the effects of Se-enriched soybean on the flavor compounds in SeSS were characterized with HPLC and SPME–GC–olfactometry/MS. Results showed that the contents of total selenium (11.1-fold), organic selenium (10.6-fold), small peptides (≤1 kDa, 25.4 %), free amino acids (FAAs, 8.67 %) and 22 aroma-active compounds in SeSS were significantly enhanced when compared to soy sauce prepared using ordinary soybean (SS, p < 0.05). Only the contents of 4-vinylguaiacol and acetic acid in SeSS were decreased by 30.5 % and 17.7 %. Further investigations found that Se-enriched soybean markedly enhanced the activities of acidic and alkaline proteases in the koji and moromi (p < 0.05), which made more proteins and large peptides degrade into small peptides, sweet and bitter FAAs. Se-enriched soybean moromi promoted the reproduction of aroma-producing Lactobacillus plantarum and Zygosaccharomyces rouxii, and more aroma-active compounds were detected in SeSS. 4-Vinylguaiacol was reduced to 4-ethylguaiacol by L. plantarum and acetic acid was converted into acetate via esterification. The work developed a widely accessible selenium supplement and a novel method to improve the flavor of soy sauce.