Aptitude à l’amélioration de la qualité physicochimique et microbiologique d’un lait fermenté (yaourt étuvé) par l’ajout de l’extrait hydrométhanolique de Mentha x piperita L.

Abstract

The objective of this study is to monitor the effect of incorporating Polyphenol-rich Hydromethanolic extract of Mentha piperita L. on the quality of a parboiled yogurt. The Peppermint (Mentha piperita L) was collected in the wilaya of Ouargla-Algeria. The extraction of phenolic compounds from peppermint was carried out by cold maceration in aqueous methanol. The solvent of the filtrate was then concentrated and the recovered extract was finally incorporated into a fermented milk (yogurt) at the rate of 0, 2 and 4%, respectively. The measurements and controls carried out in triplicate on the hydromethanolic extract of mint and the experimental fermented milks on the 1st day of the fermentation period and after 21 days of preservationin interest of: dosage of total polyphenols, dosage of flavonoids, acidity, pH , viscosity, enumeration of Streptococcus thermophilus, enumeration of Lactobacillus bulgaricus, adhesiveness, cohesiveness and freshness. The parametric results were subjected to a monofactor analysis of variance and a comparison of means according to the Newman and Keuls test; while the organoleptic data were treated statistically by Friedman's test. Peppermint extract (Mentha piperita L) rich in phenolic compounds seems to exert at high doses of 4% in fermented milk a remarkable decrease in the growth of specific lactic acid bacteria in yoghurt; Streptococcus thermophilus and Lactobacillus bulgaricus. This antimicrobial effect resulted in a loss of the rheological quality of the product (viscosity, adhesiveness and cohesiveness), particularly during 21 days of storage at 4 ° C. However, the results show that incorporating the mint extract at a rate of 2% does notaffect the quality of yogurt.