Flavor and quality characteristics of Guizhou red sour soup prepared by different artificially fortified fermentation methods

Red sour soup is a typical condiment in Guizhou Province, China. However, its flavor quality is often limited by its unstable traditional fermentation methods. In the study, red sour soup was prepared with three fermentation methods (split fortification, mixed fortification, and natural fermentation) and then various indicators of the prepared soup were determined. Compared with natural fermentation, two fortified fermentation methods could accelerate the pH decrease of red sour soup (on the 6th day pH = 3.36 & PLUSMN; 0.01 for split fortification and pH = 3.26 & PLUSMN; 0.06 for mixed fortification), increase the total number of lactic acid bacteria, total acid, umami value, and amino nitrogen content, and more efficiently control the content of nitrite and saltiness. Mixed fortification realized the contents of organic acids (26.776 & PLUSMN; 8.351 g/kg) and cis-lycopene (9.540 & PLUSMN; 0.559%). The contents of the key esters (methyl butyrate, hexyl acetate, etc.) and alcohols (2-ethylhexanol, 1-hexanol, etc.) in the red sour soup prepared with two fortified fermentation methods were higher than those in the red sour soup prepared with natural fermentation. The characteristic flavoring substances in the red sour soup prepared with split fortification were mainly leaf alcohol, ethyl butyrate, isoamyl acetate, and & alpha;-turnipene, whereas the characteristic flavoring substances in the red sour soup prepared with mixed fortification were mainly methyl butyrate, isobutyl acetate, hexyl acetate, and linalool oxide. The study provides the basis for the optimization of fermentation parameters and the quality control of red sour soup.