Molecular evolution of starch structure and sugar supply dynamics during the initial fermentation stages of Jiangxiangxing Baijiu.

The enzymatic hydrolysis of sorghum starch is fundamental to Jiangxiangxing Baijiu production. This study investigated the molecular-level degradation of starch during the initial fermentation phases by integrating GPC-MALLS-RI and HPAEC-PAD analyses. We quantified a progressive reduction in starch molecular weight and a structural shift from high- to low-degree-of-polymerization materials. Sugar profiling revealed a distinct temporal transition: heap fermentation served as the primary saccharification hotspot, predominantly accumulating glucose alongside maltose and maltotriose, while pit fermentation was dominated by glucose consumption for ethanol production. Mass balance analysis quantified substrate conversion efficiency, showing a net consumption of 18.20 g/100 g carbohydrates (dry basis) from an initial 72.67 g/100 g, with an ethanol yield of 2.34 g/100 g. Notably, proteomic detection of key amylolytic enzymes provided evidence consistent with a major contribution of the α-amylase and glucoamylase pair. These findings provide a molecular framework for understanding starch saccharification, offering a scientific basis for optimizing traditional Baijiu fermentation.