Flavor characteristics of hulless barley wine fermented with mixed starters by molds and yeasts isolated from Jiuqu

The traditional natural Jiuqu for brewing hulless barley wine contains a variety of complex microorganisms and enzymes. The uncertainty of microbial composition in Jiuqu and the existence of some miscellaneous microorganisms are not conducive to the production of high-quality hulless barley wine. In order to improve the flavor quality of hulless barley wine, the mixed starter was designed to reconstruct the fermentation microbial flora. Mold strains with high saccharification ability and yeast strains with good fermentation performance were screened from the traditional natural Jiuqu for brewing hulless barley wine and were identified. And then, mixed starters by molds and yeasts were used to ferment hulless barley wines on a laboratory scale. The physicochemical indexes, sensory evaluation, volatile flavor compounds and electronic nose (E-nose) analysis of hulless barley wine brewed by different combinations of mold and yeast were analyzed. The hulless barley wine (W4 wine) brewed by the mixed starter Q4, which combined by Rhizopus oryzae, Saccharomyces cerevisiae and Wickerhamomyces anomalus, had the best volatile flavor and sensory score. This improvement was mainly reflected in the higher content of esters (252.62 ± 0.02 mg/L) and alcohols (72.77 ± 2.03 mg/L), with esters accounting for 67.37 % of the volatile flavor compounds. In addition, the sensory score of "bitter" was the lowest in W4 wine while the scores of "sweet", "wine-aroma" and "fruit-aroma" were the highest. These results demonstrated that the mixed starter Q4 could effectively improve the flavor of hulless barley wine.