Green tea (GT) is a traditional beverage widely recognized for its health benefits. Fermentation of GT may offer additional advantages over unfermented GT by altering bioactive compounds, enhancing antioxidant activity, and promoting digestive health. The probiotic strain Lacticaseibacillus paracasei HII01 has previously shown multiple biological benefits. In this study, we aimed to optimize GT fermentation conditions to increase total phenolic content (TPC) and antioxidant activity. A Central Composite Design (CCD) with Response Surface Methodology (RSM) was applied to evaluate and optimize key fermentation parameters systematically. GT fermentation was performed using different concentrations of starter and sugar at 37 °C for 14 days, and changes in TPC and antioxidant capacity were assessed. The optimum condition for the kinetic analysis of changes in TPC, antioxidant capacity, pH, total acidity, reducing sugar, total microbial load, and representative phytochemicals has been selected. The results showed that the TPC and antioxidant capacity of fermented GT gradually increased. During fermentation, a gradual decline in pH was observed, accompanied by a corresponding increase in total acidity. The reducing sugar and total lactic acid bacteria (LAB) content increased until day 3, after which they decreased gradually. After day 21, no live LAB was detected, and no pathogens were detected throughout the fermentation. The changes in phytochemicals were correlated with the antioxidant activities of fermented GT. The study identified 15% starter and 6% sugar as the optimal conditions for producing high-quality fermented GT at 37 °C. Further studies on changes in the aroma compounds, flavor, and consumer acceptability of fermented GT are required. Since the probiotic used here has been reported to benefit humans, in vitro and in vivo studies using the HII01-mediated fermented GT may provide insights into its versatility in managing various diseases and disorders.
Choeisoongnern et al. (Fri,) studied this question.