In this study, Fuji apple juice was used as raw material for the production of apple cider by fermentation with Saccharomyces cerevisiae. Prior to alcoholic fermentation, different mass concentrations of dihydromyricetin (DMY) or rosmarinic acid (RA) were added. The fermentation kinetics was monitored. The physicochemical indices, color parameters, and aroma quality were analyzed after the completion of alcoholic fermentation. Results showed that the addition of DMY or RA to apple juice significantly accelerated the fermentation process, and the resultant cider met the basic requirements for low-alcohol fruit wine (alcohol content < 7%). Compared with SO₂ addition, RA and DMY were less effective in inhibiting the browning of apple cider, yet they did not affect the sensory score. Moreover, the browning inhibitory effect and sensory score of the RA treatment group were both higher than those of the DMY addition group. The addition of RA or DMY significantly increased the content of volatile compounds in apple cider, with a more pronounced effect being observed at 60 mg/L RA. RA significantly increased the contents of differential aroma compounds including citronellol, (E)-nerolidol, menthol, and geranyl acetone and elevated the total amount of aroma substances by 6.87%. Principal component analysis combined with sensory evaluation revealed that linalool, farnesol, ethyl decanoate, and ethyl octanoate were responsible for the floral and fruity aroma characteristics of the cider with 60 mg/L of RA added. Comprehensive analysis indicated that the addition of 60 mg/L RA to apple juice as a substitute for SO₂ not only allowed for the successful completion of alcoholic fermentation but also effectively enhanced the volatile aroma compound content and sensory quality of apple cider.

In order to improve the aroma and sensory quality of Fuji-Merlot wine, the mixing ratio between Fuji apple and Merlot grape juices was optimized and the mixed fruit juice was inoculated with non-Saccharomyces yeast and S. cerevisiae for mixed culture fermentation. The physicochemical indexes, color parameters and volatile aroma compounds of wine samples were determined, and the sensory scores were calculated using the fuzzy mathematical sensory evaluation method. The results showed that the mixing between grape and apple juices had a significant effect on the color saturation (C^*) and volatile components of apple-grape wine. Notably, the wine made from a 50:50 (V/V) mixture of apple and grape juices were characterized by bright color (luminosity (L^*) value of 76.24, red-green (a^*)) of 31.24, and C^* of 2.58) and high levels of volatile compounds including trans-nerolidol, β-damascenone, ethyl caproate, ethyl caprylate, and ethyl phenyl acetate. Non-Saccharomyces yeast had an insignificant effect on the color parameters of the wine. The wine fermented with a mixed culture of Torulaspora delbrueckii and S. cerevisiae had the largest number of volatile compounds (63) and significantly higher mass concentrations of isoamyl acetate, ethyl acetate, ethyl hexanoate, ethyl caprylate, phenethyl alcohol, 1-hexanol, and 1-heptanol than did pure S. cerevisiae fermentation and the other mixed culture fermentations. In addition, the wine had enhanced floral and fruity aromas with a sensory score of 7.6055. In conclusion, the apple-grape wine co-fermented by T. delbrueckii and S. cerevisiae was superior to apple wine fermented by S. cerevisiae in terms of sensory quality.

To explore the effect of mixed culture fermentation with non-Saccharomyces yeast (NS) and Saccharomyces cerevisiae (S. cerevisiae) on oenological parameters and aroma compounds, a model grape juice was sequentially inoculated with pairwise mixtures of indigenous Torulaspora delbrueckii, Metschnikowia pulcherrima and Hanseniaspora uvarum followed by S. cerevisiae. The fermentation kinetics and changes in the volatile profile were analyzed. The results demonstrated that sequential fermentations with single (TV, MV and HV) and mixed NS (TMV, HMV and HTV) followed by Vintage White (VW) all reduced the content of ethanol and titratable acidity while increasing glycerol levels compared with pure S. cerevisiae fermentation (VW). In addition, the contents of esters, volatile fatty acids, carbonyl compounds, and volatile phenols significantly increased as determined by gas chromatography-mass spectrometry (GC-MS). The contents of volatile compounds such as isoamyl alcohol, ethyl caprylate, ethyl decanoate, ethyl hexanoate, and octanoic acid were evidently higher in the mixed NS + VW than single NS + VW groups. Notably, the highest level of volatile compounds was observed in the HMV group. Orthogonal partial least squares-discriminant analysis (OPLS-DA) combined with odor activity value (OAV) showed that HMV fermented wine had more prominent banana-like, apple-like and floral aroma characteristics. Overall, co-fermentation with M. pulcherrima, H. uvarum, and S. cerevisiae promotes the accumulation of volatile compounds, indicating that these strains have the potential to be developed into multi-species starter cultures.

In this study, we investigated the effects of pomace maceration and mixed culture fermentation on the quality of pomegranate wine, made from Tunisian pomegranates. Single factor experiments and an orthogonal array design were jointly employed to optimize the process parameters for pomace maceration, which was conducted before fermentation. Mixed culture fermentation of pomegranate juice prepared under optimized conditions was conducted by co-inoculation of Torulaspora delbrueckii NX-1 or Metschnikowia pulcherrima NX-2 with Saccharomyces cerevisiae ES488 to explore the effects of different mixed starters on the aroma quality of pomegranate wine. The results showed that the optimum conditions for preparing pomegranate juice were maceration at 6 ℃ for 24 h after the addition of 200 g/L pomace. Mixed culture fermentation significantly increased the content of volatile compounds in pomegranate wine. In particular, co-fermentation with T. delbrueckii NX-1 and S. cerevisiae ES488 evidently increased the contents of the characteristic aroma components in pomegranate wine such as ethyl acetate, isoamyl acetate, ethyl caprylate and phenyl ethyl acetate, which imparted rich floral and fruity aromas to pomegranate wine, thereby improving the flavor complexity and richness. Meanwhile, pomace maceration followed by mixed culture fermentation could improve the antioxidant capacity of wine samples. In conclusion, the results of this study hold potential application value for improving aroma quality and antioxidant capacity of pomegranate wine.