Shelf Life Evaluation and Correlation between Changes in Volatile Compounds and Bacterial Communities in Fresh Tuber indicum Treated with Alcohol during Cold Storage

explore a simple and effective preservation technology to prolong the shelf life of fresh Tuber indicum during cold storage.

quality characteristics of fresh Tuber indicum such as sensory quality, total number of colonies, main nutrients content and volatile compounds were studied during storage at 4 ℃. High-throughput sequencing technology was used to reveal the bacterial community structure of fresh Tuber indicum during storage at 4 ℃. What’s more, the correlation analysis between the main aromatic compounds and the bacterial community structure was clarified. The 16S rRNA gene identification technology was used to identify the specific spoilage organisms those isolated from truffles during storage at 4 ℃. The results showed that the shelf life of fresh truffle soaked in 75% alcohol and vacuum packaged was 30 days during storage at 4 ℃. The contents of total sugar, total protein and crude fiber in truffle stored for up to 38 days decreased significantly in comparison with those in fresh truffle. Meanwhile, the mass loss percentage increased evidently, the content of volatile aroma compounds decreased markedly and the content of volatile off-flavor compounds increased obviously. The results of high throughput sequencing showed that Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes and Verrucomicrobia were the dominant phyla in fresh truffle during cold storage. The redundancy analysis showed that during 0–15 days of storage, the contents of nutrient components (total sugar, total protein and crude fiber) and characteristic aroma substances (1-octene-3-ol, pentyl valerate, ethyl acetate, 3-methyl-ethyl butyrate, 2-octenone, 1-octene-3-one, hexaldehyde and n-hexanol) were positively correlated with the relative abundance of Bradyrhizobium, Rhizobium, Bosea, Variovorax, Dyadobacter, Janthinobacterium and Pedobacter. The contents of total protein, 1-octene-3-ol and n-amyl pentanoate were significantly positively correlated with the relative abundance of Bosea. The relative abundance of Pseudomonas and Serratia showed a significantly positive correlation with mass loss percentage from days 15 to 38. The contents of pyridine, dimethyl ether, 3-methyl-butyric acid, hexanoic acid, heptanal, crotonol, 3-methylthiopropanol and 3-methyl-1-butanol were positively correlated with the relative abundance of Ensifer, Pseudomonas, and Serratia from days 30 to 38. The results of this study will provide a theoretical basis for the in-depth study of the spoilage mechanism of and the development of new preservation technologies for fresh Tuber indicum.