Enhancing Indica Rice Wine Quality by Adding Acid Protease and Lactobacillus Plantarum F25-4 During Soaking Process.

Indica rice is affordable and readily available, making it an excellent raw material for brewing indica rice wine (IRW). However, indica rice contains high amylose and protein content, which often results in suboptimal alcohol yield and flavor profiles. This study developed a novel synergistic soaking process combining acid protease with Lactobacillus plantarum F25-4 to address these limitations. The mixed soaking treatment significantly enhanced IRW quality, yielding 30.33% higher ethanol content with 15.2% lower residual sugar compared to conventional soaking. The treatment reduced bitter amino acids by 46.6% while increasing total esters by 43.97%, particularly phenethyl acetate, which reached 2.57 mg/L. These improvements were attributed to profound modifications during soaking: soaking water showed 175% higher acidity and 25-fold increased amino nitrogen, while treated rice exhibited complete hydrolysis of >17 kDa proteins, 37.6% reduced hardness, and 18.1°C lower gelatinization temperature. This enzymatic-microbial pretreatment synergistically enhances indica rice wine quality by optimizing rice macromolecular structures during soaking, offering a practical approach for premium rice wine production.