Ecologia da maturação do Queijo Minas Artesanal produzido na microrregião do Campo das Vertentes e sua influência na viabilidade do Staphylococcus aureus

Abstract

Artisanal Mynas cheese is very well-known and highly valued, not only in Mynas Gerais but also in other Brazilian states. Efforts have been made to reduce the maturation time stipulated in the legislation. Although there have been years of research involving its manufacturing process, studies on the viability of pathogenic microorganisms and the microbial dynamics of maturation still need to be conducted, defining the best maturation time for these cheeses with the aim of ensuring safety and the sensory quality, highly appreciated, of the product to the consumer. Thus, the objective of this project was to evaluate the viability time of Staphylococcus aureus in cheese as well as to study the dynamics of the fermentation process involving lactic acid bacteria (LAB). Ten freshly made cheeses were collected from each of the two cheese factories in the Campo das Vertentes microregion for the evaluation of S. aureus and LAB during their maturation, transported to the laboratory, where they were matured, with 5 cheeses from the control group and 5 cheeses inoculated with S. aureus producing enterotoxin type A (108 CFU/g of S. aureus), analyzed at five maturation times (0, 7, 14, 21, and 28 days) using microbiological and physicochemical methods, and the metabolome profile was also monitored. The detection of enterotoxins was carried out, and the metataxonomic study was conducted on the control group cheeses based on the sequencing of the V3-V4 region of the 16S rRNA. The physicochemical analyzes showed a significant reduction in moisture in both cheeses from the two studied cheese factories. The cheeses from São João del Rei (SJDR) tended to have a higher initial moisture content, around 48%, compared to the cheeses from Coronel Xavier Chaves (CXC) at 42.8%. The pH of the CXC cheeses started at 6.67, reduced to 6.08, and gradually increased to 6.45, with the initial pH of the control cheese being significantly higher than that of the Inoculated cheese. Time had a highly significant effect on the count of S. aureus, which decreased over the maturation period, at time 0, initial counts were 7,40 e 7,32 log CFU/g for cheeses from the CXC and SJRD inoculated groups,respectively, and at 28 days of maturation, counts were 1,27 and 1,64. The average values of LAB counts also showed a significant decline over the maturation time for all cheese factories and groups, with a marked predominance of the genus Lactococcus, which represented approximately 95% of the sequences attributed to the metataxonomic profile. The PCoA (Bray-Curtis) indicated a clear separation between the bacterial communities, suggesting a distinct microbial composition from the other samples, indicating that the bacterial community of the SJDR cheese factory at time 7 underwent significant structural changes during maturation, compared to the other samples. The results showing the absence of Salmonella spp, Escherichia coli, and Listeria monocytogenes found in the evaluation of microbiological quality throughout the entire maturation period attested to the hygienic quality of the cheese factories in the Campo das Vertentes microregion. Keywords: ripening; lactic bacteria; microbial ecology; foodborne diseases; staphylococcal enterotoxin.