Preparation of high polyphenol-low caffeine instant tea powder by exploring and regulating the changes of key...

This study unveils the changes and composition of the main functional compounds during kombucha fermentation, and introduces metal ions as nutrients to regulate caffeine content in the fermentation liquid to prepare high polyphenol-low caffeine instant tea powder. Results showed an overall increasing trend in total phenol contents of fermentation liquid with green tea leaves (GTF) during fermentation. Day 6 was the optimal fermentation time, when GTF was rich in organic acids, with a total phenol content of 3.22 g/L. The introduction of 16.28 mg/L Cu²⁺ reduced the caffeine content of fermentation liquid (Cu-GTF) to 164.29 mg/L, at which point multiple caffeine degradation pathways existed in Cu-GTF. Moreover, kombucha instant powder (Cu-KG) was successfully prepared under optimal drying conditions. Compared to commercially available products, Cu-KG exhibited a good antioxidant effect and special vanilla flavor. These results provide a theoretical foundation for the development of novel kombucha products with customized functional factors.