Étude de l’effet de l’addition de l’extrait de myrte pour la bioconservation du lait bovin.

Abstract

Myrtle is among the medicinal aromatic plants, traditionally used as a treatment against several diseases, in the form of food or spice for a long time. This plant which is found in the Mediterranean and in the eastern regions, in our study, we obtained it from the eastern region of Algeria, more precisely from Mila. Our work aims to study the effect of adding the crude extract of M. communis to bovine milk in order to improve their microbiological qualities. A hydroethanolic extraction was carried out to determine the resulting yield which was equal to 20.73%, followed by the estimation of the content of total polyphenols using the Folin-Ciocalteu reagent and sodium carbonate (NaCO3) with a value equal to 690.29 ± 8.80 μg Eq AG/mg of extract, and content of flavonoids by aluminum chloride (AlCl3) with a value equal to 18.79 ± 1.60 μg EQ/mg of hydroethanolic extract. We studied the antibacterial activity which was tested in vitro on six referenced strains of Gram positive and Gram negative according to the method of diffusion on solid medium from discs impregnated with different concentrations of Myrtle extract. Our results show that our extract exerted a remarkable effect against the majority of the strains tested, especially those with Gram positive, Staphylococcus aureus ATCC2856 (17.73 ± 0.873), Staphylococcus aureus ATCC25923 (17.37 ± 0.970), Enterococcus faecalis ATCC49532 (22 .79±3.528) mm in diameter. Bacterial growth kinetics was monitored during cold storage of milk for 8 days at regular intervals and growth parameters were determined. Thus the favorite results which improve the quality of milk are the values of kinetic parameters which belong to the concentration of 5 mg/ml G=2.0555± 0.69 (53h), with a maximum cell density (μmax) equal to 8.503 ± 0.401 log CFU/ml and a strongest growth rate (Xmax) equal to 1.0897 ± 0.203 Log CFU.mL−1 /day. These results are encouraging and open a promising avenue for the use of the hydroethanolic extract of M. communis as a natural antimicrobial agent for milk preservation.