Effect of temperature of storage on the composition and microbiological quality of raw milk

The aim of the study was to evaluate the quality of refrigerated raw milk from dairy farms located in Southwestern state of Goias during the rainy and dry seasons. Fresh milk samples were collected from bulk tank and stored for 0, 24, 48 and 72 h for the evaluation of psychrotrophic microorganisms counts, titratable acidity, chemical composition, somatic cell count (SCC) and total bacterial count (TBC). In the rainy season, the average temperature of the refrigerated raw milk samples was 17.4, 6.0, 6.1 and 5.3°C and in the dry period, the average temperature was 9.2, 2.4, 3.8 and 1.4°C for 0, 24, 48 and 72 h of storage, respectively. The physicochemical characteristics of refrigerated milk were consistent with the maximum limits established by Brazilian legislation after storage for 72 h in expansion tanks; however, in the dry period, refrigerated milk should not remain stored for more than 24 h due to the high TBC values. The results of the microbiological analyses revealed failures in the cleaning of equipment and utensils used for milking, demonstrating need for greater hygiene in the collection and maintenance of refrigerated milk at the production source. Key words: Storage time, mastitis, refrigerated milk, hygiene.