Effects of cooking processes on total polyphenolic contents in seeds extracts of 17 varieties of Bambara groundnut (Vigna subterranea (L.) verdcourt)

Author(s): Abel Mbaiogaou, Adama Hema, Michel Naitormbaide, Eloi Pale, Mahama Ouédraogo, Yaya Mahmout, Mouhoussine Nacro

The effects of three cooking modes commonly used in sub-SaharanAfrica on the total polyphenolic contents of 17 varieties of groundnut from the Institute of environment and agricultural research (INERA) of Burkina Faso and the Chadian Institute of agronomic research for development (ITRAD) of Chad have been studied. These total polyphenolic contents were assessed before and after cooking using a common and simple method based on Folin-Ciocalteu’s reagent. Total antioxidants (TAC) and anthocyanins (TAT) contents of raw seeds were respectively assessed using the Ferric Reducing Antioxidant Power (FRAP) and differential pH methods. TAC was ranged from5.018 (for KVS314) to 10.727mg of Tolox Equivalents/g (forKVS225).KVS97,M4 andKVS350 varietieswere distinguished byTAT greater than 160 µg/g dry seeds. Results of the determination of total polyphenolic contents (TPC) after cooking indicated that the three cooking processes had negative effects which involved decreases in TPC in studied seeds. Indeed, there were rates of decrease about 13.53%, 31.19% and 52.06% respectively for cooking processes by roasting, at pH7 and at pH8.Among these three cooking modes, cooking by roasting allowed better retention (86.47%) of total polyphenolic contents.

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