Effects of baking and steaming on volatile and non-volatile metabolites in Yanshu 25 juice before and after fermentation

This study examined the effects of different heating techniques, specifically baking and steaming, on the physicochemical properties, volatile organic compounds (VOCs), and non-volatile compounds (non-VOCs) of fermented Yanshu 25 juice. The results indicate that Maillard reactions, caramelization, Strecker degradation of phenylalanine, degradation of lipids and carotenoids, and the thermal release of glycosidically bound terpenes during baking intensify the interconversion of soluble sugars, organic acids, and amino acids in Yanshu 25 juice. Fermentation was found to increase the contents of sucrose, mannitol, lactic acid, TPC, TFC, and antioxidant activities. Notably, baking significantly reduced sucrose and citric acid levels while enhancing the concentrations of glucose, maltose, fructose, lactic acid, and carotenoids in Yanshu 25 juice. The "Yanshu 25 + baking + fermentation" (SBF) group exhibited elevated levels of umami (Asp) and aromatic (Glu) amino acids, as well as volatile aroma compounds such as 2-heptanone (banana aroma) and 1-octen-3-one (sweet aroma). Additionally, SBF reduced the levels of undesirable flavor compounds, including 3-octanone, thereby improving the overall flavor quality. In summary, baking as a heating method significantly enhances both the nutritional and flavor profiles of fermented Yanshu 25 juice. Through multidimensional analysis, this study explores and develops distinctive processing methods for tuber-based beverages using various processing techniques for Yanshu 25, and quantitatively characterizes their unique indicators. These findings provide significant guidance for the future processing and production of related raw materials, achieving high-value utilization and comprehensive exploitation of agricultural products.