Effects of processing methods on phenolic compositions, anti-oxidant activities and α-glucosidase inhibitory ability of two buckwheat varieties

Abstract

Buckwheat (BW), as an important raw material rich in phenolic/flavonoid compounds, has been widely used to make various functional foods. However, there are few studies investigating the effects of processing methods on the phenolic compositions and bio-activities of two BW varieties. In this study, several processing methods including steaming, roasting, and enzymatic and fermentation were applied to treat two BW varieties. After processing, the highest contents of TPC (16.2 ?? 0.7 mg gallic acid equivalent/g dried weight for tartary BW and 11.4 ?? 0.5 gallic acid equivalent/g dried weight for common BW) and TFC (36.5 ?? 1.2 mg rutin equivalent/g dried weight for tartary BW and 20.7 ?? 0.6 mg rutin equivalent/g dried weight for common BW) were obtained in BW fermented with Monacus anka. However, steaming, roasting, and enzymatic methods significantly decreased TPC and bio-activities of two BW varieties. HPLC results showed rutin, quercetin and ferulic acid were the most abundant phenolic compositions in two varieties BW. Compared to the control, the contents of rutin, quercetin and ferulic acid in fermented BW were significantly higher. Moreover, Monascus anka BW fermented with M. anka showed the stronger antioxidant activities and ??-glucosidase inhibition activities than BW treated by other processing methods. In addition, a significantly positive correlation existed between the investigated bio-activities and the phenolic compositions in BW samples. In short, it is concluded that fermentation should be taken into consideration in the processing of BW to enhance the contents of phenolic compounds, and then improve the functionality of BW.