Influência da maturação nas características físico-químicas e microbiológicas do queijo Minas artesanal produzido com leite proveniente de vacas com alelo A2 para β-caseína

Abstract

The quality of food is essential to ensure sanitary safety and reduce the microbiological risks of the final product. To achieve this, it is crucial to guarantee the quality of raw materials and water used in production. Minas artisanal cheese (QMA), a dairy product that is traditionally important to Minas Gerais' culture and economy, is frequently questioned regarding its sanitary safety due to its production involving raw milk. Unpasteurized milk can serve as a source of pathogenic microorganisms, increasing the risk of foodborne illnesses. The production of QMA involves complex physicochemical and microbiological transformations, which not only contribute to the cheese's sensory characteristics but also promote the multiplication of desirable bacteria, such as lactic acid bacteria (LAB), while inhibiting the growth of pathogenic and spoilage microorganisms. A recent alternative gaining prominence in the dairy industry is the use of A2 milk in dairy product manufacturing. A2 milk is produced by cows that carry the A2 allele for β-casein and contains exclusively A2 β-casein. When digested, it does not release or releases only minimal amounts of the bioactive peptide beta-casomorphin-7 (BCM-7). In this context, the objective of this study was to perform the microbiological and physicochemical characterization of QMA produced with milk from cows carrying the A2 allele for β-casein in the region of Lagoa da Prata, Minas Gerais, under different maturation periods during both the dry and rainy seasons. Sample collections took place in two seasons, dry and rainy. The study included an analysis of coliforms, mesophilic bacteria, and the physicochemical characterization of the water used on the dairy farm. It also assessed the microbiological quality of raw A2 milk and whey starter used in QMA production. Additionally, Enterobacteriaceae, coliforms at 30°C and 45°C, Staphylococcus spp., Staphylococcus coagulase-positive, molds and yeasts, LAB, and Salmonella spp. were analyzed in QMA at one, seven, 14, 21, 45, and 60 days of maturation. Aflatoxin M1 (AFM1) was examined in QMA samples at one and 60 days. The isolated LAB strains were characterized, with 42 strains identified. Microbiological results for water showed a count of <1.0 log CFU/mL for aerobic mesophilic microorganisms and <0.9 MPN/mL for coliforms at 30°C in both seasons, confirming compliance with state and federal regulations. Regarding physicochemical analyses, pH, total hardness, alkalinity, and conductivity parameters were within the recommended limits. Analyses of raw A2 milk demonstrated compliance with current legislation, meeting quality standards. The season significantly influenced the count of LAB, fat content, lactose levels, and somatic cell count. Regarding the whey starter, microbial contamination was higher during the rainy season, except for molds and yeasts, which showed a 3.00 log CFU/mL higher count compared to the dry season. A significant difference was observed in the titratable acidity of the whey starter, being approximately 2.0 g lactic acid/100mL higher in the rainy season. For QMA, the maturation period had a significant effect (P < 0.05) on most analyzed microorganisms, except for coliforms at 45°C and Staphylococcus coagulase-positive. Seasonal variations influenced only Staphylococcus spp. counts. Overall, LAB showed a tendency to increase during maturation, while Enterobacteriaceae decreased. Regarding physicochemical analyses, seasonal variations significantly affected pH levels, chlorides, fat, and protein content in cheese. All QMA samples met the quality standards required by Minas Gerais regulations after 14 days of maturation in the rainy season and seven days in the dry season.