Effet des extraiits phénolliiques des écorces de grenade (Puniica granattum.. L) sur ll''évollutiion des paramètres physiicochiimiiques et miicrobiiollogiiques d''un llaiit fermenté de type yaourt.

Abstract

This study aims to evaluate the antioxidant properties of bark extracts of Punica granatum L, and valorize them by introducing them into a yogurt in order to obtain a functional nutritional and therapeutic nutrient. The evaluation of these extracts is carried out by the method of reduction of the free radical DPPH. The extraction is done by the use of the three solvents; methanol, ethanol and acetone. Quantification of the total polyphenols showed the richness of the methanolic extract whose content is 2,940 ± 0.087g EAG / g freeze-dried. From the results of the DPPH test, the methanolic extract exhibited the best radical inhibitory activity DPPH is a 50% inhibitory concentration (IC50) equal to 0.68 mg / ml. In addition, the three extracts also showed efficacy in comparison with ascorbic acid (IC50 of 0.714 ± 0.004 mg / ml). The experimental work was completed by a study which is summarized in the preparation of a fermented milk with the incorporation of fruit extract of Punica granatum, in order to study the effect of the latter on the evolution of the parameters. physicochemical and microbiological properties of the finished product. Experimental results show that the addition of phenolic extract of pomegranate peel in fermented milk reduced pH and increased acidity and viscosity. In addition, the extract appears to exert a stimulating effect on the growth of lactic acid bacteria (Streptococcus thermophilus and Lactobacillus bulgaricus). In conclusion, the results obtained indicate that the bark of Punica granatum L. is a natural source of antioxidants and could be used in therapy.