Affiliation:
1. Departamento de Nutrición, Bromatología y Tecnología de los Alimentos, Facultad de Veterinaria, Universidad Complutense, Ciudad Universitaria, Madrid 28040, Spain
2. Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, United Kingdom
Abstract
ABSTRACT
Variability in the numbers of bacteria remaining in saline solution and whole milk following mild heat treatment has been studied with
Listeria innocua
,
Enterococcus faecalis
,
Salmonella enterica
serovar Enteritidis, and
Pseudomonas fluorescens
. As expected, the most heat-resistant bacterium was
E. faecalis
, while
P. fluorescens
was the least heat resistant, and all bacteria showed greater thermal resistance in whole milk than in saline solution. Despite the differences in the inactivation kinetics of these bacteria in different media, the variability in the final number of bacteria was affected neither by the species nor by the heating substrate, but it did depend on the intensity of the heat treatment. The more severe the heat treatment was, the lower the average number of surviving bacteria but the greater the variability. Our results indicated that the inactivation times for the cells within a population are not identically distributed random variables and that, therefore, the population includes subpopulations of cells with different distributions for the heat resistance parameters. A linear relationship between the variability of the log of the final bacterial concentration and the logarithmic reduction in the size of the bacterial population was found.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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