Optimization of extraction conditions for the maximum recovery of L‐theanine from tea leaves: Comparison of black, green, and white tea

Abstract Background The caffeine content of tea (Camellia sinensis (L.) Kuntze) can counteract the anti‐anxiety effects of L‐theanine. This study aims to find out the extraction method of L‐theanine and caffeine from tea leaves to obtain the highest L‐theanine and the lowest caffeine content. For this purpose, L‐theanine and caffeine contents from three tea types (white, black and green) were extracted under different time and temperature conditions and their levels were determined in a single high‐performance liquid chromatography (HPLC) analysis. Also, this study is the first to attempt to optimize the tea extraction conditions by maximizing the ratio of L‐theanine to caffeine concentration. Results The results show that white tea extracted for 5 min at high temperatures (90–100°C) had the highest L‐theanine level (21.52 mg/mL). Whereas, white tea, extracted for 5 min at low temperatures (10–11°C), had negligible caffeine (0.006 mg/mL). The caffeine content was relatively high in the extracts prepared from all types of tea under high temperatures (90–100°C). Whereas, caffeine level was low in tea extracted at low temperatures. The L‐theanine‐to‐caffeine ratio was largest for white tea extracted at 10–11°C for 5 min (L‐theanine/caffeine ratio > 200), and this ratio was lowest (0.96) for black tea extracted at 90–100°C for 30 min. Conclusion According to these data, the temperature and time of extraction have significant effects on the amount of L‐theanine and caffeine extracted from Camellia sinensis (tea). In addition, white tea drinks prepared for 5 min at 10–11°C, could be recommended to people intolerant of caffeine side effects.