Impact of metabolite transformations on off-flavor profiles of pasteurized drinking yogurt in non-microbial conditions

Despite the absence of living microorganisms, pasteurized drinking yogurt (PDY) undergoes significant flavor changes over a six-month shelf life. This study aims to elucidate the mechanisms driving these flavor transformations. PDY samples with varying shelf lives (0, 30, 60, 90, 120, 180, and 210 days) were directly collected from the production line and comprehensively analyzed using non-targeted metabolomics techniques. The analysis revealed that metabolite transformations in PDY occurring independently of microorganisms primarily involve pathways such as starch and sucrose metabolism, amino sugar and nucleotide sugar metabolism, and purine metabolism. Correlation analysis identified core metabolites significantly associated with shelf life, serving as potential predictive indicators and playing crucial roles in generating off-flavors in PDY. Moreover, excessive or unbalanced oxidation and decomposition of lipids and lipid-like molecules produced peculiar smells, diminishing PDY's taste quality. These core metabolites, which change significantly over shelf life, can predict PDY's shelf life with high accuracy (R2 = 92%), and their potential transformation pathways were inferred. This study enhances our understanding of flavor changes and quality control in PDY, offering substantial significance.