Effect of Co-fermentation of Yeast with Different Lactobacillus Species on the Quality of Stauntonia chinensis Ferment

To investigate the effect of enhanced fermentation of different lactobacillus species on the quality of Stauntonia chinensis ferment, the fresh Stauntonia chinensis pulp was utilized as the raw material. Lactobacillus Royceae (LRL), Lactobacillus rhamnosus (LRT), Lactobacillus plantarum (LPZ), and Lactobacillus acidophilus (LAS) combined with yeast were used in the co-fermentation. Changes in conventional physicochemical indexes, functional components, antioxidant activity, and flavor components were systematically analyzed during the fermentation process. The results indicated that the total acid content increased gradually, while pH, soluble solids, and triterpene content decreased. After 15 days of fermentation, the LRT fermentation system exhibited the highest triterpene content at 5.57 mg/100 mL, while the LAS system showed the highest polyphenol content at 4.27 mg/mL. In addition, the DPPH radical scavenging capacity and SOD enzyme activity were highest in the LRT system, whereas the hydroxyl radical inhibition rate was highest in the LRL system. Using gas chromatography-mass spectrometry (GC-MS) combined with odor activity value (OAV) analysis, it was found that except for the LRL fermentation system, the types and contents of esters increased in the other three systems. Notably, a total of 87 volatile components were detected in LRT fermentation system, predominantly comprising esters (172.68 mg/L) and alcohols (151.60 mg/L). Among these, 30 volatile components had an OAV≥1, and the primary key volatile components were ethyl isobutyrate, ethyl caprate, phenylethanol and nonanal. Principal component analysis (PCA) indicated that the types and contents of Stauntonia chinensis ferment prepared by composite strains differed significantly from those of unfermented Stauntonia chinensis. This fermentation process enriched the composition of volatile components in Stauntonia chinensis ferment, and the LRT fermentation system had the richest flavor profile. In conclusion, the quality of Stauntonia chinensis ferment was influenced by the co-fermentation of yeast with different lactobacillus species. The LRT fermentation system demonstrated superior performance in terms of functional component content, antioxidant activity, and flavor profile improvement.