Optimization of Bran-koji Production and Its Impact on Huangjiu Quality

The effects of bran types and solid-state fermentation conditions on the enzyme activity of bran-koji inoculated with Penicillium oxalicum M1816 were investigated, and the bran-koji with the highest enzyme activity was applied to Huangjiu production to evaluate its effects on the phenolic content, physicochemical indexes, and sense of Huangjiu. The results showed that when the diameter of bran was 20-mesh, the enzyme activity of bran-koji was corn bran>wheat bran>oat bran>rye bran. The highest enzyme activity in corn bran-koji was achieved under the following conditions: Glacial acetic acid was used to adjust the pH of the solid medium to 6.5, the initial moisture content of the bran-koji was 85% (V/W), the incubation temperature was 30 ℃, and the incubation time was 120 h. Compared with factory Huangjiu, the total amount of phenolic acids in the Huangjiu produced by adding corn bran-koji was 116.48 mg/L, which increased to 1.1-folds in comparison with that of the Huangjiu produced by adding no-corn bran-koji (55.53 mg/L). The volatile phenolic compounds of 4-ethylphenol, 4-ethylguaiacol, 4-vinylguaiacol, guaiacol, and vanillin were increased significantly (P<0.05), the medicinal aroma of the Huangjiu was obviously enhanced, and the physicochemical indexes were all in accordance with the national standard of Huangjiu. The optimal fermentation condition of corn bran-koji with Penicillium spp. was confirmed, and corn bran-koji could improve the contents of phenolic acids in Huangjiu. The research provides a technical reference for the brewing of Huangjiu with medicinal aroma characteristics and rich in phenolic substances.