Résumé:
Lactic acid bacteria are used in the preparation of many dairy products, including fermented milk, L’ben and yogurt. They also have an effective role in improving organoleptic quality. The objective of our work is first to characterize the preparation of a fermented milk based on lactic
strains isolated locally and by the use of two types of milk (skimmed milk and goat; milk), then to study the kinetics of acidification during fermentation, the coagulant activity of the strains and the microbiological quality of the end product obtained; coagulated milk;. Eight lactic strains were tested (Lactobacillus plantarum, lactobacillus fermentum, Enterococcus faecium, Lactococcus lactis ssp lactis).
The kinetics of acidification was carried out by monitoring the evolution of pH and acidity. The microbiological quality of the finished product was determined by the search and enumeration of the following germs; total and faecal coliforms, total germs, yeasts and molds and staphylococcus aures. The results show that the majority of the strains tested have the capacity for coagulation and the formation of curd and present a good progressive production of lactic acid in skimmed milk compared to Goat's milk. In general, the results indicate that the speed of acidification in all strains is average and varies from species to species.
The two finished products analyzed (fermented milk based on skimmed milk and fermented milk based on goat's milk) have good microbiological quality and are very satisfactory from a hygienic and sanitary point of view, the values found for all the germs counted are lower than the required standards.
