Correlation between flavor compounds and microorganisms of Chaling natural fermented red sufu

Sufu, a traditional Chinese fermented soybean product, has a variety of flavors due to fermentation. However, the relationship between the formation of these flavors and microorganisms in the fermentation process is not clearly understood. In this study, the dynamic changes of the microbial diversity, free amino acids (FAAs), free fatty acids (FFAs) and volatile flavor compounds (VFCs) of Sufu during the post-fermentation process were investigated. The results indicated that a range of VFCs, including phenylacetaldehyde, linalool, 2-pentyl-furan were formed during the post-fermentation. The main FFAs found in these Sufu samples were linoleic acid, oleic acid and arachidic acid and the most predominant FAA was glutamic acid, which highly contributed to the taste characteristic of Sufu. The correlation analysis result discovered that Leuconostoc, Lactobacillus, Weissella, Debaryomyces, Tausonia and Pichia were the main microorganisms responsible for the flavor formation of Sufu. In addition, it was found for the first time that Chaling red Sufu could produce a cream milk aroma of nonanoic acid, which strongly positive correlated with Rhodotorula. It is expected that these findings will provide new insight into the flavor formation of conventionally fermented soybean foods.