Ngabirano, ElieSous la direction : Pr Nzigamasabo Aloys2026-01-212026-01-212025-07https://repository.ub.edu.bi/handle/123456789/2202Mémoire présenté et défendu pour obtention d’un diplôme de Master en sciences des aliments et nutrition Option : Technologie et qualité des alimentsProteins are essential nutritionally, economically, and sociocultural, and are especially present in ruminant milk, whose processing into cheese allows for better preservation. Rennet, a coagulating enzyme extracted from the stomachs of young ruminants, mainly milk-fed calves, is most often used in cheese processing, making it expensive and limited in availability. The study demonstrates that papain and bromelain can coagulate cow's milk, with variable results depending on the quantity used, and the processed cheeses retain their organoleptic qualities for 9 months of ripening and more. FP1 cheese, coagulated with 1 g of papaya leaves, did not form a curd, while at 3 g, an adequate curd formed. FA2 cheese, made with 40 ml of pineapple juice, was rated higher in taste, odor, and color than the one coagulated with 3 g of papaya leaves. A low dose of enzymes is recommended to preserve the organoleptic quality of the cheese. Although papain has superior proteolytic activity, bromelain is preferred for its sensory qualities. This study represents the first investigation into the production of Gouda cheese using natural coagulants, although challenges remain regarding enzyme extraction and the texture of the final product. Microbiological analysis reveals the absence of harmful staphylococci and coliforms, but a high presence of lactic acid flora and slight contamination by yeasts and molds. Ripening conditions influence microbial growth.