Effect of co‐inoculations of <i>Saccharomyces cerevisiae</i> and grape endophytes on the fermentation property, organic acid, and volatile aroma compounds

Grape endophytic fungi (EFFs) have rich secondary metabolic pathways that can synthesize bioactive substances and various enzymes, which may contribute to the improvement of wine quality. In order to investigate the effect of EFFs on fermentation characteristics and chemical components, fermentations by co-inoculations of Saccharomyces cerevisiae and five EFF strains at different concentrations were performed in this study. It was found that EFFs affected the fermentation rate and are related to the genus of EFFs and inoculation amount. Among them, strains RH48 and RH34 facilitated the fermentation process at an optimal concentration of 3.5 g/L. Strain RH34 had acid-increasing potential and effectively increased malic and succinic acid contents. In terms of volatile aroma compounds, CS13 3.5 g/L and RH34 3.5 g/L treatment showed significant enhancement of acetate esters content by 91.04% and 61.34%, respectively, whereas RH48 3.5 g/L and CS13 3.5 g/L showed significant enhancement of fatty acid ethyl ester content by 52.14% and 48.45%, respectively. In addition, strain CS13 at 3.5 g/L also significantly increased the content of terpenes, higher alcohols, and aromatic compounds, showing great potential in improving the aroma quality (floral, fruity, etc.) of wine. The results of the present study may be useful for the innovation of wine fermentation aids and the improvement of wine quality.