Effet anti-brunissement enzymatique de différents extraits de Phoenix dactylifera L., de trois variétés (Deglet Nour, Ghars et Adala) de la région de Metlili- Ghardaïa

Abstract

I

Mots clés: dattes de Phoenix dactylifera L., brunissement enzymatique, polyphénol oxydase, peroxydase, inhibition, pyrocatéchol, gaïacol.

Enzymatic browning control was essential to maintaining the commercial quality of food products and meeting consumer needs. Therefore, the production of dates must take into account their post-harvest conservation to maintain their freshness and prevent their degradation and alteration. This study is consecrated to the research for inhibitors of natural origin of the two enzymes: peroxidase and polyphenol oxidase extracted from the dates of Phoenix dactylifera L., of three varieties (Deglet Nour, Ghars and Adala) harvested from the Metlili – Ghardaïa region; as an assay to help alleviate some of the problems of dates enzymatic browning. First, enzymatic extraction was carried out using two methods, distilled water and theTamopn -PVP. Thus, the raw extracts were tested directly for their enzymatic activity, using gaïacol and pyrocatechol as substrates for both POD and PPO enzymes respectively. The results obtained showed positive activity and the Tampon PVP extracts showed better rates of enzymatic activity compared to the Water extracts. Also, the influence of substrate concentration on the enzymatic activity of the POD and PPO shows a classic Michaelian response with variable values of Vmax and Km. The evaluation of the anti-peroxidase activity indicates that the different extracts studied are able to inhibit the POD, while no effect is noted with the variety Deglet Nour. However, the same extracts showed no inhibitory efficacy against PPO. Also, the inhibition of PPO was tested with the ascorbic acid, the results show that ascorbic acid caused a significant decrease in the activity of PPO with percentages of inhibition of up to 53.09% for TPS-PVP enzymatic extract of the Adala variety. A mixed non-competitive and an uncompetitive inhibition type was obtained with the extracts at the more potent inhibition rate.