Microbiological and physicochemical characteristics of Chihuahua cheese manufactured with raw milk

Chihuahua cheese is traditionally produced in the State of Chihuahua, Mexico, with raw milk, which involves potential bacterial outbreaks. The objective of this work was to characterize the cheese-making process of Chihuahua cheese, including the determination of cheese composition and microbiological determination of pathogens, indicators and Lactic Acid Bacteria (LAB). Ten different cheese factories were sampled where cheese manufacturing protocols were documented. Also, samples of raw milk, curd, cheddaring, and final product were taken. Pathogens, indicators (total mesophilic bacteria, coliforms, coagulase-positive Staphylococci and Salmonella) and LAB were quantified in all samples. Proximal analysis of the final product was also completed. Although process steps were similar, there were significant variations in relevant parameters such as temperature, pH, and time. Regarding microbiological analysis, coliforms (5.9-7.4 Log10 CFU/g) and total mesophilic counts were high (8.8-9.2 Log10 CFU/g), while counts of S. aureus were within the range of 2.1-2.3 Log10 CFU/g. The microbial count of lactobacilli was lower in milk and higher in the final product. The highest counts of enterococci (6.97 Log10 CFU/g) and thermophilic lactobacilli (8.16 Log10 CFU/g) were observed in the final product. Microbial counts were different in all dairies and LAB groups varied during the manufacturing process. Principal Component Analysis grouped data by type of sample or process analyzed, rather than by dairy location. Manufacturing standardization, incorporation of good manufacturing practices, and milk pasteurization with the use of a starter culture, can improve the overall quality of Chihuahua cheese. The balance between the sensorial and physicochemical properties of the artisanal product will assure that Chihuahua cheese is not a risk of food-borne outbreaks for consumers.