INFLUENCE OF MILK FAT IN THE RESISTANCE OF Mycobacterium fortuitum TO SLOW PASTEURIZATION

Abstract

ortuitum. Milk samples were divided into two portions, whole and skimmed, each part was inoculated with M. fortuitum and then distributed in tubes for quantification of the agent during pasteurization, in a water bath. As samples were diluted and plated on Lowenstein-Jensen (37 °C/5 days), the count results were expressed as log10 CFU/mL. The heat treatment reduced 4.4 log10 CFU/mL for goat whole milk (2.8% fat), 4.9 log10 CFU/mL for skim goat milk (0.3%), 3.9 log10 CFU/ml for whole bovine milk (5.9%), and 5.4 log10 CFU/mL for skim bovine milk (0.2%), without significant difference, possibly because of the low number of samples. Values of D65 °C were, respectively, 10.51 minutes, 8.61 minutes, 18.02 minutes, and 7.82 minutes and the low R2 value of the straight line equations indicated that other factors, in addition to the ones studied, influenced the heat death of the agent. The results suggest a trend of influence by fat milk, and by the animal species on the decay rate of M. fortuitum, and that pasteurization was less effective over M. fortuitum in whole bovine milk.

Keywords: fat content;