Effets antimicrobiens de l’extrait aqueux de Mentha pipérita .L récolté à Ouargla-Algérie sur les germes Streptococcus thermophilus et Lactobacillus bulgaricus et impact sur la qualité d’un yaourt étuvé

Abstract

The experimental study is devoted to the evaluation of the inhibitory effects of the aqueous extract of Mentha piperita L on the growth of specific yogurt germs, and on the other hand the impact of the addition of this extract. extracted in different doses as a natural additive on the evolution of the physicochemical, microbiological and organoleptic parameters of a fermented milk (parboiled yoghurt type) during the periods of fermentation and post acidification. The aqueous extract of the plant under study was obtained by maceration with water. the recovered extract was then diluted with sterile distilled water at concentrations of 0.20,40.60.80, and 100%. Incorporation tests of mint extract at 0, 2, 4 and 6% were also carried out in fermented milk type steamed yoghurt. The various measurements and controls were carried out in triplicate tests and focused on: direct contact test, disk diffusion test, minimum inhibitory and bactericidal concentration (MIC and CMB), pH, acidity, viscosity and organoleptic tests. The results were analyzed for variance and averaged by Newman and Keuls. The aqueous extract of Mentha piperita L seems to exert a bactericidal inhibitory effect on the growth of yogurt lactic bacteria: Sreptococcus thermophilus and Lactobacillus bulgaricus. The addition of aqueous peppermint extract to the fermented milk has relatively reduced the acidity, pH, viscosity and even increase of the germs Streptococcus thermophilus and Lactobacillus bulgaricus. However, the fermented milk supplemented with 2% and 4% aqueous mint extract was very well appreciated by the tasting panel, just like the standard yoghurt.