Proteolytic and lipolytic microbiota of refrigerated raw milk from northeast and southern regions of Brazil Microbiota proteolítica e lipolítica de leite cru refrigerado da região nordeste e sul do Brasil

The shelf life of milk and milk derivatives is directly related to the microbiological quality of refrigerated raw milk. Spoilage microorganisms with proteolytic and/or lipolytic properties are primarily responsible for the decrease in the quality of milk, which is reflected in the shelf life of pasteurized milk and all derivatives. The aim of this study was to determine the spoilage microbial load of refrigerated raw milk from the northeast and southern regions of Brazil, which have different climatic and technological conditions of production. We evaluated 46 samples of milk from the state of Parana in the southern region, and 10 samples of milk from the state of Maranhao in the northeast region, totaling 56 samples collected from November 2013 to November 2014. The producers of Parana were divided into large (20) or small (26) according to the average daily production. All producers of Maranhao were considered small (<500L/day). The proteolytic and lipolytic microorganism counts were conducted in milk agar and tributyrin agar, respectively. Milk from the large producers of Parana had average counts of 1.4 × 10 4 CFU/mL for proteolytic microorganisms and 1.2 × 10 3 CFU/mL for lipolytics microorganisms, significantly (p <0.05) lower than the small producers in the same state, and the producers of Maranhao. Producers of Maranhao had counts of 1.1 × 10 5 CFU/mL for proteolytic microorganisms and 2 × 10 5 CFU/mL for lipolytic microorganisms, with the proteolytic count significantly lower than that of small Parana producers. The amount of proteolytic and lipolytic spoilage microorganisms in milk is influenced by the adaptation of the microorganisms to cold, promoted by the cooling of milk, which is practiced less frequently in the country’s northeastern region. The amount of spoilage microorganisms is also affected by the implementation of milking hygiene practices, which reduce contamination. Such practices are more frequently and efficiently implemented among large producers with more advanced technology, which can improve the microbiological quality of raw milk, thus increasing the shelf life of pasteurized milk, and reducing problems in UHT milk as well as milk derivatives.