Performance of selected P. fermentans and its excellular enzyme in co-inoculation with S. cerevisiae for wine aroma enhancement

- P. fermentans strain from Chinese liquor pit has the potential to improve wine aroma.
- Extracellular enzyme treatment promotes the release of varietal aroma compounds.
- Esterase activity during mixed fermentation was superior to that of control.
- Sensory analysis indicated the odor risk of mixed fermentation.

This study evaluated aroma enhancement in dry white wines made via a specific Pichia fermentans strain and its excellular enzyme in co-inoculation with Saccharomyces cerevisiae. The inoculation ratios of two yeasts ranged from 0.1 to 10 and fermentations with pure S. cerevisiae were utilized as control. Esterase activities that expressed as C2-C8 chain substrate specificity were surveyed during mixed fermentation. Finally, wine aroma was analyzed via GC-MS and a trained sensory panel. The results revealed that C2-C8 esterase activities were superior during mixed fermentation to the control. Mixed fermentations significantly increased the contents of acetates, ethyl esters, fatty acids, and numerous other fermentative volatiles; particularly those of medium-chain fatty acids and their corresponding esters, with an increased inoculation ratio of the isolate. Extracellular enzyme treatment highly improved the release of varietal aroma compounds, such as terpenols, C13-norisoprenoids, and C6 compounds. Sensory analysis indicated that the risk of negative earth odor emerged in the wine characterized by strong sweet and acid fruit trait. Therefore, mixed fermentations at yeasts inoculation ratios between 1:4 and 4:1 may provide better fermentation strategies for appropriate wine aroma enhancement.