The chemical and microbiological characteristics of Awa‐bancha, Japanese post‐fermented tea

Abstract

Awa‐bancha is a traditional Japanese post‐fermented tea made by residents in Tokushima Prefecture in the Shikoku region. Tea was picked, boiled, rubbed, anaerobic fermented, and dried in the process of making Awa‐bancha. Nevertheless, the details of making Awa‐bancha differs depending on the producer, such as how the tea leaves are boiled, the weight of the stones, and the length of anaerobic fermentation. Therefore, the objective of this study was to examine the chemical and microbiological characteristics of Awa‐bancha among different producers. The result explicated that the total phenolic compounds of Awa‐bancha extracted by water at 95°C for 10 min ranged from 20.41 ± 0.66 to 35.49 ± 3.90 mg GAE/g DW, the average DPPH activity was 877.4 ± 307.81 mmol Trolox/g DW, and the average α‐glucosidase inhibition activity (IC50) was 2.27 ± 0.63 mg/ml. The result revealed that Awa‐bancha differed due to differences in statistical analysis labels (p ≤ 0.05), resulting in various chemical functionality among the producers. Suggesting that processing or fermentation of Awa‐bancha may influence the bioactive compound in tea leaves changing from epicatechin (EC) to other compounds as well as HPLC analysis results show Epigallocatechin gallate (EGCg) is the main bioactive compound in Awa‐bancha. The higher the acidity produced from the fermentation process, the higher concentration of the reducing sugar and total phenolic compounds, which affect antioxidant activity and α‐glucosidase inhibition activity. Furthermore, the results show that Lactiplantibacillus plantarum is the dominating bacteria in Awa‐bancha which is well known as a probiotic and beneficial to the human gastrointestinal tract by producing antimicrobial substances. According to this study, based on its health benefits, Awa‐bancha could be possibly considered one of the functional drinks in the food industry. Novelty Impact Statement This study focused on the diversity of Awa‐bancha, a traditional post‐fermented tea from various producers in Kamikatsu Town, Tokushima, Japan and discovered a statistically significant difference in reducing sugar content and total phenolic content. Additionally, it was discovered that the chemical functionality of the Awa‐bancha product was related to its higher acidity, higher polyphenolic content, antioxidant activity, and glucosidase inhibitory activity.