Background Milk quality, particularly somatic cell count (SCC) and psychrotrophic bacterial load, plays a critical role in cheese manufacturing, affecting yield, composition and technological performance. The presence of these factors is associated with enzymatic activity that can compromise protein integrity and product stability during storage, making their control essential for the dairy industry. Objective This study evaluated the effects of SCC and psychrotrophic bacteria levels in milk on the yield, physicochemical composition, proteolysis, microstructure and functional properties of mozzarella cheese during refrigerated storage. Methods Raw milk was classified into three groups according to SCC and psychrotrophic bacterial levels: G1 (227 600 cells/mL; 4 log cfu/mL), G2 (285 000 cells/mL; 5 log cfu/mL) and G3 (310 200 cells/mL; 6 log cfu/mL). Mozzarella cheeses were produced on an industrial scale and analysed in triplicate over 90 days of storage. Physicochemical, textural, mineral, proteolysis and microstructural analyses were performed. Data were evaluated using Tukey's test and response surface methodology. Key Results Milk with SCCs above 285 000 cells/mL and psychrotrophic levels above 5 log cfu/mL reduced cheese yield by approximately 1.8% and negatively affected protein and fat recovery. G3 cheeses showed increased proteolysis, higher moisture, structural weakening, reduced hardness and greater free oil release. Microstructural analysis confirmed progressive matrix degradation, especially in G3. Storage time intensified these effects, with significant deterioration observed after 90 days. Scientific or Industrial Implications The results demonstrate that controlling SCC and psychrotrophic bacteria in milk is essential to ensure optimal mozzarella yield, composition and functional quality, directly impacting industrial efficiency and product performance.
Bezerra et al. (Wed,) studied this question.