Process Optimization and Quality Analysis of Fermented Foxtail Millet Alcoholic Beverage with Liqueur Koji

In order to increase the utilization rate of foxtail millet resources, the brewing conditions of fermented foxtail millet alcoholic beverage were optimized by single-factor experiment and response surface methodology. For the fermentation of the liquor koji, foxtail millet was used as the primary ingredient. As part of the comprehensive evaluation index, which included the soluble solid, total acid, and sensory score, the nutritional value, antioxidant potential, and volatile flavoring compounds were also identified. Results showed that the optimal fermentation conditions of foxtail millet alcoholic beverage were as follows: addition amount of liqueur koji 1%, fermentation time 3 d, fermentation temperature 32 ℃. The soluble solids of the beverage were 22.05%, total acid was 19.33 g/L, sensory score was 89.37, alcohol level of 0.7%vol, flavone was 66.78 mg/L, and polyphenol was 65.13 mg/L. In the beverage, potassium was the most abundant mineral and nicotinamide was the most abundant vitamin. The clearance rates for DPPH radical, ABTS⁺ radical, and hydroxyl radical were 73.19%, 34.29% and 53.72%, respectively. In addition, a total of 46 volatile flavor compounds were found in the beverage, with esters and alcohols being the most prevalent ones. These molecules were recognized as flavor compounds giving the fermented foxtail millet alcoholic beverage a distinct scent. As a result, the product serves as a theoretical guide for the creation of functional foods using foxtail millet as a raw ingredient. It is nutrient-dense and has a pleasing aroma and flavor.