Counting, isolation and characterization of psychrotrophic bacteria from refrigerated raw milk

This study aimed to quantify, isolate and characterize psychrotrophic bacteria from refrigerated raw milk produced at the 'Mata' Region of Minas Gerais State and Souteast of Rio de Joneiro State, Brazil. Raw milk samples, were collected at the farms, from 20 collective refrigerated tanks and 23 individual refrigerated tanks. The psychrotrophic bacteria counting ranged from 10(2) to 10(7) Colony Forming Units (CFU) ml(-1) for both types of refrigerated tanks, but most of the collective tanks showed counts higher than 1 x 10(5) CFU ml(-1). Predominance of psychrotrophic gram-negative bacteria (81.2%) that were identified bv API 20E and API 20NE as belonging to genera: Aeromonas, Alcaligenes, Acinetobacter, Burkholderia, Chryseomonas, Enterobacter, Ewingella, Klebsiella, Hafnia, Methylobacterium, Moraxella, Pantoea, Pseudomonas, Serratia, Sphingomonas Yersinia were oserved. Tilt, gram-positive bacteria (18.8%), were identified by API 50 CH, API Coryne and API Staph, to genera: Bacillus, Brevibacterium, Cellum / Microbacterium, Kurthia e Staphylococcus. The API systems utilized could not identify all the bacterial isolates. Pseudomonas was the genus most isolated with P fluorescens as the predominant species. Most of the isolates presented proteolytic and/or lipolytic activity at 4 degrees C 7 degrees C and 10 degrees C showing high potential for milk and milk products spoiloge. The results indicated that more attention must be taken to the procedures necessaries to reduce milk contamination with psychrotrophic bacteria.