A Comparative Study of Yeasts for Rosa roxburghii Wine Fermentation

Effect of SO2, glutathione, and glutathione-rich inactive dry yeast on the color, phenolic compounds, ascorbic acid, and antioxidant activity of Roxburgh rose wine

Conventional methods for inhibiting browning in wine are not suitable for cili (Roxburgh rose) wine, which is naturally rich in ascorbic acid and subject to restrictions on SO2 addition. In this study, the capacity of various additives to suppress the browning of cili wine caused by ascorbic acid degradation was investigated. SO2, pure reduced glutathione (GSH), regular inactive dry yeast (IDY), and IDY with various levels of glutathione enrichment (g-IDY) were separately introduced into cili wine following the completion of alcoholic fermentation. Over a period of 12 months, the color parameters, levels of ascorbic acid, phenolic compounds, antioxidant activity, and GSH content of the aged cili wine were analyzed. Among the investigated additives, g-IDY exhibited the strongest inhibitory effect on browning. Moreover, adding 800 mg L-1 g-IDY increased the total reducing power and residual GSH content by factors of 1.52 and 2.44, respectively, with respect to those of the SO2-treated cili wine, thus enhancing its antioxidant capacity. Using ultra-performance liquid chromatography-tandem mass spectrometry analysis, a total of 22 monomeric phenolic compounds were identified. After g-IDY treatment, the contents of 15 easily oxidizable o-diphenols decreased, preventing the depletion of ascorbic acid as an antioxidant. As a result, the levels of ascorbic acid and total phenolics were 1.5-fold and 1.17-fold higher than those in the SO2-treated wine, respectively. This study demonstrates that g-IDY provides a new approach to preventing the browning of wine caused by ascorbic acid degradation. PRACTICAL APPLICATION: Cili wine, characterized by its high ascorbic acid content, can decelerate cellular senescence and bolster immune function, which has contributed to its popularity. Ascorbic acid, a potent antioxidant, can be spiked into white wines to significantly enhance their antioxidative properties. Nevertheless, the high ascorbic acid content in cili wine renders it susceptible to oxidation under both aerobic and anaerobic conditions, which alters the wine's hue from golden to dark brown, thus diminishing its commercial value. Overcoming this browning associated with ascorbic acid degradation is therefore of considerable importance and could facilitate the advancement of the cili industry.

Effect of Hanseniaspora uvarum-Saccharomyces cerevisiae Mixed Fermentation on Aroma Characteristics of Rosa roxburghii Tratt, Blueberry, and Plum Wines

Hanseniaspora uvarum, a non-Saccharomyces cerevisiae species, has a crucial effect on the aroma characteristics of fruit wines, thus, attracting significant research interest in recent years. In this study, H. uvarum-Saccharomyces cerevisiae mixed fermentation was used to ferment Rosa roxburghii Tratt, blueberry fruit wine, and plum fruit wines using either a co-inoculated or a sequentially inoculated approach. The three fruit wines' volatile aroma characteristics were analyzed by headspace-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that the mixed inoculation of H. uvarum and S. cerevisiae reduced the alcoholic content of Kongxinli fruit wine. Moreover, H. uvarum-S. cerevisiae fermented Rosa roxburghii Tratt, blueberry, and plum fruit wines and further enriched their flavor compounds. The overall flavor characteristics of sequentially inoculated fruit wines differed significantly from those fermented with S. cerevisiae alone, although several similarities were also observed. Sequential inoculation of H. uvarum and S. cerevisiae positively affected the mellowness of the wine and achieved a better harmony of the overall wine flavors. Therefore, H. uvarum-Saccharomyces cerevisiae mixed fermentation can improve the complexity of the wines' aromatic composition and empower them with a unique identity. In particular, H. uvarum-Saccharomyces cerevisiae blueberry wine produced by mixed fermentation had the widest variety and content of aroma compounds among the fermented wines. Therefore, H. uvarum-Saccharomyces cerevisiae mixed-fermentation inoculation in the three fermented fruit wines significantly increased the aroma compound variety and content, thus, enriching their aroma richness and complexity. This study is the first comparative evaluation of the aroma characteristics of different fruit wines fermented with a mixed inoculation of H. uvarum and S. cerevisiae and provides a preliminary guide for these fruit wines produced with non-Saccharomyces yeast.