Fermented or not fermented: a comparative study of the biological activities and microbiomes of a non‐fermented green tea and a five‐year‐old fermented tea prepared from young leaves of Shan tea

• Published in: International journal of food science & technology Vol. 59; no. 7; pp. 4693 - 4700
• Main Authors: Tran, Phuc N. H., Nguyen, Yen T. M., Nguyen, Minh Q., Nguyen, Trung‐Dũng, Tran, Hanh T. M.
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01-07-2024
• Subjects: Anticancer; antioxidant; Antioxidants; Comparative studies; Cytotoxicity; Fermented food; fermented Shan tea; Food contamination; Food poisoning; green Shan tea; Green tea; Hepatocytes; Liver cancer; microbiome; Microbiomes; Microorganisms; Tea; Toxicity
• ISSN: 0950-5423; 1365-2621
• DOI: 10.1111/ijfs.17194

Summary
Camellia sinensis var. shan is a special tea variety in Vietnam that is in high demand, especially its fermented products. This study compared the total polyphenol content (TPC), antioxidant activity, cytotoxicity, and microbiome of a green Shan tea and a five‐year‐old fermented Shan tea. Folin–Ciocalteu, DPPH and SRB assays were used for TPC, antioxidant activity and cytotoxicity evaluation. The isolated microbes were morphologically and molecularly identified. The TPC (126.59 mg g−1) and antioxidant activity (IC50 of 284.82 μg mL−1) of the green tea were significantly higher than those of the fermented tea. However, the latter showed a significantly higher cytotoxicity against liver cancer cells (inhibiting 73.84% cells at 1 mg mL−1). Notably, the green tea had a negligible number of microbes, but the fermented tea had a much richer microbiome with Aspergillus restrictus (4.7 × 104 CFU g−1), A. ruber (1.76 × 103 CFU g−1), A. pseudoglaucus (1.32 × 103 CFU g−1), A. cibarius (8.8 × 102 CFU g−1), Bacillus cereus (1.13 × 104 CFU g−1), Peribacillus frigoritolerans (4.0 × 102 CFU g−1) and B. amyloliquefaciens (2.0 × 102 CFU g−1) present. These microbes are either harmless or beneficial, except for B. cereus (can cause food poisoning at >106 CFU g−1). The fermented tea would appear to have some advantages over the green tea. However, the presence and density of B. cereus should be monitored.
The fermented tea would appear to have some advantages over the green tea. However, the presence and density of B. cereus should be monitored.