Soluble and bound phenolic contents and antioxidant capacity of tef injera as affected by traditional fermentation

摘要

Highlights ? Fermentation has improved the TPC and antioxidant potential of tef injera. ? Fermentation has improved both soluble and bound phenolic contents. ? Tef injera fermented for 72h revealed the highest TPC and antioxidant potential. ? Individual phenolic compounds of soluble extract increased after 72h fermentation. ? Brown tef varieties showed higher TPC and antioxidant contents than white varieties. Injera, a fermented pancake, is a major food in Ethiopia but there is limited information on its phenolic and antioxidant potential. The aim of this study was to investigate the effect of fermentation on soluble and bound phenolic profiles and antioxidant potential of 0, 24, 72 and 120h fermented injera from 4 tef varieties of brown and white color. The contribution of soluble phenolic extracts to the total phenolic content ranged from 14 to 17% and 17–32%, before and after fermentation, respectively. Gallic, protocatechuic, vanillic, syringic, p-coumaric, salicylic, ferulic acid, catechin and naringenin were identified and quantified both in the fermented and unfermented injeras from Quncho and Zezew tef varieties. After fermenting for 72h, the majority of the phenolic compounds increased in the range of 42–1805% in soluble and decreased by 2–100% in bound extracts in both varieties. FRAP values of the soluble and bound phenolic extracts of injera increased by 54–138% and 30–40%, respectively. Total ABTS values, but not DPPH, improved with fermentation. Fermentation for 72h showed the highest increase in total phenolic and antioxidant contents. Brown seed colored varieties (Zagurey and Zezew) showed superior total phenolic and antioxidant contents compared to the white varieties (Quncho and Tsedey).