Résumé:
The present study aims to follow the antimicrobial effect of the aqueous extract of Peppermint (Mentha x Pepirita L.) harvested in the region of Ouargla-Algerie on the specific Streptococcus thermophilus germ of yoghurt. The aqueous extract of Mentha x Pepirita L. subject of the study was obtained by maceration in water of the leaves of the plant. The extract recovered after filtration and evaporation was then diluted with sterile distilled water at concentrations of 0, 20,40,60,80 and 100%. The different measurements and controls were carried out in triple tests and included: the direct contact test, the disc diffusion test, the minimal inhibitory concentration and the minimal bactericidal concentration. The results underwent an analysis of mono-factorial variances and a comparison of the means according to the Newman and Keuls test.
The aqueous extract of Mentha piperita L. is relatively rich in phenolic compounds (45.41 mgEAG/ml extract) and seems to have a bactericidal inhibitory effect on the yoghurt-specific lactic germ Sreptococcus thermophilus.
No growth of the studied germ was noticed in the pure undiluted extract of peppermint whose antimicrobial effect was very close to gentamycin; with an inhibition rate of approximately 87.71.
It is possible to incorporate the extract of Mentha piperita L. in yogurt at a rate of less than 20%. Nevertheless, this incorporation can slow down to 32% the growth of the Sreptococcus thermophilus germ in the product.
