Influence of marginal cooling on the psychrotrophic growth and acidifying metabolism of milk microbiota

Abstract

Brazil is the sixth largest producer of milk, amounting to 27 billion liters per year, although roductivity is one of the lowest in the world. In order to obtain a better quality product, the Ministry of Agriculture published in 2002, Instruction nº51, which established the milk refrigeration at 4°C, after milking and delivery (bulk) for dairy plant within 48 hours. The cooling associated with lack of hygiene in obtaining highlighted a group of microorganisms with high deteriorating potential: the psychrotrophics. Cooling is an important technological tool of conserv tion to preserve the original quality of the product , but must be done right, because marginal cooling temperatures, above 7 ° C, promotes not only a greater number of genera psychrotrophic, as well as a mixed characteristics of microflora (mesophilic / psychrotrophic), with intense metabolic activity of lipo-proteolytic and acidifying, reducing the quality of milk and its derivatives. Based on the informations given, the work in question is to determine how the use of marginal cooling influences the psychrotrophic bacterial growth, and further quantify the expression of metabolic activities of a transience microbiota, that modify some physical and chemical parameters milk, and therefore the loss of sensories characteristics of the general product. The results indicated that only the cooling to 4°C proved to be feasible, as a factor inhibiting the metabolic activities acid-producing bacteria. The work also suggests greater rigor in compliance with hygienic measures, as the most efficient way to achieve both microbiological and physical-chemical laid down in legislation, as well as the temperature of incubation, the initial bacterial count was also important for maintaining the sensories characteristics milk.