Analysis of quality and volatile flavor substances of six kinds of commercial Douchi

In order to provide data support and references for the development and flavor improvement of Douchi products, using six kinds of commercial common Douchi from different production areas with different fermentation types (numbered as DC1-DC6) as the research objects, the basic nutritional components, free amino acids, and nucleotides were determined, and their taste activity value (TAV) and equivalent umami concentrations (EUC) were calculated. The volatile flavor compounds of Douchi were analyzed using HS-SPME-GC-MS, and the results were compared with sensory evaluation for comprehensive evaluation. The results showed that the content and proportion of umami amino acids in Luoding Douchi (DC3) were significantly higher than those in other Douchi (P < 0.05), while Zhangjiakou Douchi (DC6) had the highest content of umami nucleotides. Luoding Douchi (DC3) had the highest EUC value. The ranking of comprehensive sensory scores for six kinds of Douchi was DC1 > DC3 > DC2 > DC5 > DC4 > DC6, and Yongchuan Douchi (DC5) had the highest aroma sensory score. The quality and flavor of Douchi varied in different regions, and were closely related to the fermentation strains. Aspartate, glutamic acid, and ornithine were the main umami substances in Douchi. Acids, aldehydes, and esters were the main volatile flavor compounds in Douchi. Aspergillus fermentation produced more umami amino acids and pleasant flavor. Mucor fermentation had unique and rich flavor, but insufficient umami flavor, bacterial fermentation produced higher flavor nucleotides, but insufficient aroma.