Effects of Sequential Inoculation Fermentation on Quality and Metabolite Profiles of Blueberry Juice Jiaosu and Blueberry Pomace Jiaosu

Majiang blueberry, a national geographical indication product of Majiang County in Qiandongnan Miao and Dong Autonomous Prefecture, Guizhou Province, has been widely supplied across China due to its superior quality. To improve comprehensive utilization rate of Majiang blueberry fruits and enhance release of bioactive substances, blueberry juice Jiaosu and blueberry pomace Jiaosu were prepared through sequential inoculation with Saccharomyces cerevisiae and Lactiplantibacillus plantarum. The effects of microbial fermentation on the substance transformation of blueberry Jiaosu were elucidated through metabolomics and KEGG pathway enrichment analysis. Additionally, product quality was evaluated by sensory evaluation and antioxidant activity. The results showed that sequential dual-strain fermentation significantly increased the contents of total phenols, total acids and γ-aminobutyric acid, as well as the activity of superoxide dismutase in both types of blueberry Jiaosu. A total of 152 metabolites were identified in both blueberry Jiaosu products before and after fermentation, with sugars and organic acids being the predominant metabolites. 49 differential metabolites (VIP≥1, P<0.05), including 19 sugars, 11 organic acids, 3 alcohols, 3 esters, and 9 other metabolites were screened between the two blueberry fermentates by orthogonal partial least squares-discriminant analysis. KEGG enrichment analysis indicated that carbohydrate metabolism was the primary conversion pathway altering the metabolic profile of blueberry Jiaosu, while fermentation of blueberry pomace additionally involved other major pathways, including unsaturated fatty acid biosynthesis and glyoxylate and dicarboxylate metabolism. After fermentation, blueberry juice Jiaosu exhibited significant improvements in all antioxidant activity indicators and received an overall sensory score of 83.70. In contrast, blueberry pomace Jiaosu demonstrated superior hydroxyl radical scavenging ability, with a 52.8% reduction in IC₅₀, and achieved an overall sensory score of 72.20. It is expected that this study could provide theoretical references for the development of Majiang blueberry functional fermented products, as well as improve the comprehensive utilization rate and advance the intensive processing of Majiang blueberry fruits.