Effect of co-fermentation of Rhodotorula mucilaginosa with Saccharomyces cerevisiae on the quality and flavor profile of cider

During the natural fermentation of fruit wine, different yeast strains with specific fermentation characteristics and metabolic processes have an important influence on the quality and flavor complexity of fruit wines. Rhodotorula mucilaginosa is a non- Saccharomyces yeast species with low fermentation activity. It is typically involved in the first stage of fruit wine fermentation and is commonly isolated from apple and grape orchards. This investigation evaluated the effect of simultaneous and sequential fermentations of Saccharomyces cerevisiae CGMCC 2.3854 and two selected indigenous R. mucilaginosa strains on the fermentation process, quality, and flavor profile of ciders. Results showed that mixed fermentation enhanced the brightness, altered the organic acids content, and improved the clarity and flavor complexity of the ciders. Compared to Sc cider, Rh-Sc cider showed significantly higher ABTS and DPPH free radical scavenging activities. In particular, Rh-Sc cider had the highest acetate esters content, in which both isoamyl acetate (313.69 ± 29.56 μg/L) and phenethyl acetate (115.82 ± 9.02 μg/L) were significantly higher than those of other ciders, which enhanced the fruity and floral notes. Moreover, Rh-Sc cider showed the highest overall sensory quality. This investigation provides an effective strategy for enhancing the sensory and flavor complexity of cider through the simultaneous fermentation of Rh and Sc.