Effet d’ajout de l’extrait aqueux de Mentha piperita. L sur la qualité d’un yaourt étuvé au cours de la conservation.

Abstract

This experimental study aims to determine the effect of the aqueous extract of Mentha x piperita L on the quality of a fermented milk like yoghurt steamed during its conservation at 4°C. To achieve this objective, we followed the impact of the addition of the aqueous extract of the aerial part of the plant harvested in Ouargla - Algeria at different doses on the evolution of the physico-chemical, microbiological and organoleptic parameters of the experimental products during the fermentation and post-acidification periods. The extract of the plant under study was obtained by maceration with water for 6 hours followed by vacuum evaporation. Tests of incorporation of the pure mint extract at 0, 2 and 4% were carried out in triple trial preparations of fermented milks such as steamed yoghurt. The various measurements and controls were carried out on : Dosage of total polyphenols, dosage of flavonoids, pH, acidity, viscosity, germ count (Streptococcus thermophilus and Lactobacillus bulgaricus), Adhesiveness, Cohesiveness and freshness. The parametric results underwent an analysis of variance and a comparison of the means according to the Newman and Keuls test; while the non-parametric organoleptic data were statistically processed by the Friedman test. Peppermint was found to be very rich in phenolic compounds and poor in flavonoid constituents. The bioactive compounds contained in the aqueous extract revealed a remarkable inhibitory effect on the growth of the yoghurt-specific lactic germs: Streptococcus thermophilus and Lactobacillus bulgaricus. This antimicrobial effect led to a notable decrease in the acidity, viscosity and rheological qualities of the experimental fermented milks when added to a severe dose of 4% aqueous extract of peppermint. It is, however, possible to incorporate the aqueous extract of Mentha piperita L at a low dose of 2% and manufacture an alicamentous fermented milk having all the physicochemical and organoleptic criteria of a steamed yoghurt.