Caractérisation des aptitudes technologiques d’un Lactococcus lactis isolé des produits laitiers locaux

Abstract

This study aims to enhance the local microbial heritage through the use of a strain of Lactococcus lactis (from the LSTPA laboratory) for the manufacture of a traditional fermented milk of the Raïb type. The aim is to use local Hamra sheep’s milk in order to offer a standardized, high-quality and perfectly reproducible finished product. The experimental approach is based on three fundamental steps ensuring the quality and traceability of Raïb. It begins with the characterization of raw milk, involving physico-chemical analyses to assess its functional composition and microbiological examinations, including the enumeration of total and lactic flora, in order to validate the technological suitability of the raw material. The second phase corresponds to the manufacturing process itself, which consists of inoculating sheep’s milk with a Lactococcus lactis strain selected for its controlled technological performance, before conducting fermentation under strictly controlled incubation parameters. Finally, the protocol concludes with the analysis of the finished product, where the Raïb is subjected to physico-chemical tests and sensory tests to ensure its conformity and taste quality. Hamra sheep’s milk analyses reveal an excellent processability (pH 6.29, density, 1046g/L of lactose 6.09 g/L of fat 2.79 g/L of protein matter 4.17 g/L), a total flora of (5×〖10〗^6) CFU/ml and a lactic flora of (4.32×〖10〗^4 ) CFU/ml. Seeding with the indigenous strain Lactococcus lactis induces rapid acidification, reaching the isoelectric point after 24 hours at 30 °C. The resulting stabilized Raïb has a pH of 4.7 and an acidity of 82 °D, and is distinguished by excellent organoleptic quality rated 6,59/20, combining a smooth texture with a typical aromatic profile. This work demonstrates the technological and economic interest of the development of local resources (Hamra sheep breed and indigenous microbial strain). The optimization of this process makes it possible to formulate an innovative, healthy and reproducible fermented milk, thus opening up opportunities for the local food industry.