Effects of Torulaspora delbrueckii on physicochemical properties and volatile flavor compounds of navel orange wine

Torulaspora delbrueckii is a non-Saccharomyces cerevisiae that is widely used to improve the flavor of fruit wine. To investigate the effect of T. delbrueckii (Td) NCUF305.2 on the quality of navel orange wine (NOW), the physicochemical characteristics and volatile compounds of NOWs inoculated with different numbers of Td NCUF305.2 were evaluated. Results showed that the contents of ethanol and organic acids were increased by mixed fermentation. The esters contents in three mixed fermentation samples increased by 0.14–36.05% than those of pure fermentation with Sc NCUF309.2. The acetate esters contents in NOWs were significantly (p < 0.05) increased by mixed fermentation, especially in MF2 (mixed fermentation of Td NCUF305.2 and Sc NCUF309.2 at an inoculum ratio of 10:1) (8.76 mg/L). Moreover, the ethyl esters content in MF2 (1.15 mg/L) was also the highest among the mixed fermentation samples (0.69–1.15 mg/L). These compounds could give NOW strong fruity, flowery, and sweet scents. In addition, the contents of phenethyl alcohol, citronellol, and cis-carveol in MF2 were the highest.