# Enhancing the Content of Hesperidin and Nobiletin in Citrus Wines through Multi-Strain Fermentation
## 3 Results
### Physicochemical Properties and Antioxidant Activity of Nanfeng Tangerine Wine  
The diversity of microbial strains in the multi-strain combination fermentation system and the complex interactions between strains can produce Nanfeng tangerine wines with different characteristics. The physicochemical properties and antioxidant activities of different Nanfeng tangerine wines were obtained through chemical and instrumental analysis, as shown in Table 3. Pure culture fermentation with Sc exhibited the strongest fermentation performance and the highest ethanol production, reaching 11.13% (\(v/v\)), consistent with previous research findings [23; 24]. The use of multiple strains in the fermentation process led to a notable decrease in the alcohol level of the mandarin wine, as non-_Saccharomyces_ yeast have a less efficient fermentation ability for ethanol and a lower conversion efficiency of sugar into ethanol [25]. The ethanol levels from (Ce.Hg)-10-Sc, (Ce.Ht)-10-Sc, and (Hg.Ht)-10-Sc sequential fermentation methods were notably higher than other multi-strain combination fermentation methods, with similar results to Hg-10-Sc sequential fermentation (Table 3). This suggests that sequential fermentation methods enhanced ethanol production in this experiment. With the exception of Sc(Ce.Hg.Ht)-1:1, the remaining sugar levels in multi-strain combination fermentation techniques were notably lower compared to Sc and Hg-10-Sc groups. This could be attributed to the intricate microbial fermentation process that led to the conversion of sugar into substances other than ethanol. In comparison to fermentation using only Sc in pure culture, multi-strain combination fermentation methods showed a significant increase in total acidity content, which can be attributed to the metabolic processes of non-_Saccharomyces_ yeast converting sugars into acidic compounds during fermentation. The antioxidant capacity of wines from multi-strain combination fermentation was not weakened compared to the juice, indicating that multi-strain fermentation does not affect the antioxidant capacity of the wine. The 1:1 multi-strain combination fermentation group had significantly lower ethanol content than  
Figure 1: Sugar consumption kinetics and growth kinetics of yeast strains during fermentations. Abbreviations: Sc, _S. cerevisiae_; Ce, _C. ethanolica_; Hg, _H. guilliermondii_; Ht, _H. thailandica_. Data shown are the mean \(\pm\) SD of triplicates. Sc, making it suitable for the production of low-alcohol fruit wines, and the antioxidant activity was not significantly reduced, making it appealing to a broader audience. Enhancement of Hesperidin and Nobletin Content in Wine through Multi-Strain Combination Fermentation  
Seven types of flavonoids were detected in the wine produced by multi-strain combination fermentation methods (Figure 2), including naringin, neohesperidin, hesperidin, neohesperidin, eriocitrin, hesperetin, and nobletin. Notably, hesperetin and nobletin are flavonoids newly formed after alcohol fermentation, not present in the juice, and are derived from the microbial transformation of flavonoids such as hesperidin. The highest content of hesperetin was produced by the Sc:(Ce.Ht)-1:100 combination, reaching 4.12 \(\pm\) 0.08 mg/L, followed by the Sc:(Ce.Hg)-1:1 combination with a content of 4.08 \(\pm\) 0.06 mg/L. The highest content of nobletin was in the (Hg.Ht)-10-Sc combination, reaching 1.04 \(\pm\) 0.05 mg/L, significantly higher than other multi-strain combinations, and the hesperetin content produced by the (Hg.Ht)-10-Sc combination was also relatively high (4.04 \(\pm\) 0.02 mg/L), making it the optimal combination among these multi-strain fermentations for enhancing the content of hesperetin and nobletin in wine. The potential mechanism involves the enzymatic deglucosylation of new hesperidin and hesperidin in fruit juice by strains during the multi-strain joint fermentation process of Nandfeng Tangerine fruit wine.