Comparison of Nutritional Composition, Aroma Compounds, and Biological Activities of Two Kinds of Tartary Buckwheat Tea

Tartary buckwheat tea (TBT) is becoming increasingly popular for its unique flavor and health benefits. However, there is little information regarding the differences in nutritional quality among different kinds of TBT. Two kinds of TBT samples, whole grain tea (WGT) and whole plant tea (WPT), were collected from markets in China. The content of their nutritional compositions, including protein, amino acids, starch, fat, fatty acids, and flavonoids, as well as aroma compounds, were determined. Antioxidant and α‐glucosidase inhibitory activities were also evaluated. WPT showed higher levels of protein and fat relative to WGT, but the content of essential amino acids and fatty acids was lower. WPT contained more total flavonoids with quercetin as the predominant flavonoid (81%), while rutin was the principal flavonoid compound (86%) in WGT. GC‐MS analysis indicated that there were some differences in the aroma compound profile between WGT and WPT, though 14 aroma compounds were identified in both of them with 3‐ethyl‐2,5‐dimethyl‐pyrazine as the predominant compound. In addition, WPT showed superior antioxidant and α‐glucosidase inhibitory activities than WGT. However, the total flavonoid content determined in tea soup was decreased by 60% and 98% compared with that in the alcohol extracts of WGT and WPT, respectively. The antioxidant and α‐glucosidase inhibitory activities of tea soup were also lowered, especially for WPT. The differences between 2 kinds of TBT might be due to the variety of raw materials and processing methods. Diversified plant materials and scientific processing technologies should be taken into account to develop a nutritional and healthy TBT product. WPT contained higher protein and total flavonoids, and demonstrated superior antioxidant and α‐glucosidase inhibitory activities. However, the dissolution rate of flavonoids in the tea soup of WPT was extremely low, this was due to the water insolubility of its primary flavonoid quercetin, which comes from the conversion of rutin. Processing methods, such as hydrothermal treatment, should be applied to inhibit the conversion of rutin into quercetin and to develop a nutritional and healthy TBT product.