Changes in antioxidant activity of lotus (<i>Nelumbo nucifera</i>) leaf tea during the manufacturing process

This study aims to evaluate the changes in the content of bioactive compounds and the antioxidant capacity of lotus (Nelumbo nucifera Gaertn.) leaf tea throughout the production process. The results show that leaf age significantly affects the accumulation of bioactive compounds, with mature leaves having the highest total polyphenol content and total flavonoid content. After processing, all tea samples showed increased antioxidant activity due to the heat process, helping to release bound phenolic compounds and inhibit the enzyme polyphenol oxidase. A 10% moisture reduction before fermentation resulted in the highest antioxidant activity (85%), while excessive moisture reduction (> 15%) decreased total polyphenol content and antioxidant activity. The best fermentation conditions were determined to be 40 °C for 5 h. Additionally, the best hot extraction conditions for the finished tea were 95 to 100 °C for 6 to 8 min, which allowed to obtain the highest phenolic content without causing thermal degradation.