Partial Characterization of a New Peptide from Ivorian Red Onion that Inhibits Polyphenol Oxidase and Enzymatic Browning of Edible Yam (Dioscorea cayenensis-rotundata cv LongbÔ )

Abstract

The enzymatic browning of the yam was retarded by addition of fresh onion extract. The maximal activity of polyphenol oxidase inhibitor was increased with higher fresh onion extract concentrations. The inhibitor was a peptide and inhibited the polyphenol oxidase non-competitively. It was stable at pH 6.6 in phosphate buffer for 120 min at 35oC. Rapid inactivation occurred from 50 to 60oC and it was completely inactivated at 65oC after 1h30 min incubation. From 40 to 60oC, the activation energy value for thermal inactivation of the peptide was calculated to be 109.93kJ/mol. The D-values showed that the thermal treatment had more influence on the inactivation of the peptide.