Fermentation temperature affects yogurt quality: A metabolomics study

As consumers continue to savor different high-quality yogurt in recent years, refined and differentiated processing of yogurt and improving process conditions have now become the developing trends in yogurt processing. In this study, fresh milk was used as a raw material and Lactobacillus bulgaricus and Streptococcus thermophilus were used as fermentation strains to yield yogurt at different fermentation temperatures (30, 37, 40, 42, and 45 °C). The nutritional quality, physicochemical characteristics, texture, and flavor of the prepared yogurts were evaluated, and the metabolites produced during yogurt fermentation were analyzed using non-targeted metabolomics. The nutritional quality (free amino acids, fatty acids), physicochemical properties (chromaticity, water holding capacity), texture and flavor of yogurt samples were significantly changed under different fermentation temperature. In addition, 85 (30UR, 55DR), 55 (17UR, 38DR), 84 (35UR, 49DR) and 85 (46UR, 39DR) metabolites were identified from 30vs42, 37vs42, 40vs42 and 45vs42, respectively. The main metabolites identified were lipids, lipid-like molecules, organic acids and their derivatives, and organoheterocyclic compounds. Among them, lipids and lipid like molecules were the most abundant. The results from our study can serve as a guide for the production of yogurt at various temperatures.