Comparative evaluation of the effects of natural and artificial inoculation on soybean paste fermentation

Abstract

Soybean pastes fermented with natural (NIS) and artificial (AIS) inoculation were prepared to evaluate their fermentation characteristics, flavor compounds and microbial community compositions across an entire fermentation period. The results showed that the initial concentrations of free amino acids and aroma compounds were higher in NIS than in AIS, whereas it was opposite at the end of fermentation. A larger variation of flavor compounds was observed in AIS, which was associated with higher level of microbial metabolism during AIS fermentation. Penicillium and Tetragenococcus were the dominant microbial genera in NIS, while Aspergillus and Pediococcus were predominant in AIS. Correlation analysis of flavor compounds and microbial community dynamics during NIS and AIS fermentation revealed the specific role of microbial taxa in metabolite transformations. Pediococcus acidilactici could be the key microorganism strongly associated with 23 flavor compounds during AIS fermentation. Further, Aspergillus oryzae and Pediococcus acidilactici were primarily linked to amino acid metabolism in AIS, whereas Penicillium and Yaniella were found associated with aroma compounds, Tetragenococcus_sp_JNURIC_D6 and Candida solani with that of organic acids in NIS. These findings provide substantial data on the development of flavor-enhancing fermentation starter culture and the better control of flavor ripening in soybean paste production.