Effect of pH and water activity on the growth limits of Listeria monocytogenes in a cheese matrix at two contamination levels

dc.contributor.author	Schvartzman, MS	en
dc.contributor.author	Belessi, C	en
dc.contributor.author	Butler, F	en
dc.contributor.author	Skandamis, PN	en
dc.contributor.author	Jordan, KN	en
dc.date.accessioned	2014-06-06T06:51:17Z
dc.date.available	2014-06-06T06:51:17Z
dc.date.issued	2011	en
dc.identifier.issn	0362028X	en
dc.identifier.uri	http://dx.doi.org/10.4315/0362-028X.JFP-11-102	en
dc.identifier.uri	http://62.217.125.90/xmlui/handle/123456789/5430
dc.subject.other	water	en
dc.subject.other	article	en
dc.subject.other	bacterial count	en
dc.subject.other	cheese	en
dc.subject.other	fermentation	en
dc.subject.other	food contamination	en
dc.subject.other	food control	en
dc.subject.other	food handling	en
dc.subject.other	growth, development and aging	en
dc.subject.other	human	en
dc.subject.other	Listeria monocytogenes	en
dc.subject.other	metabolism	en
dc.subject.other	methodology	en
dc.subject.other	microbiology	en
dc.subject.other	pH	en
dc.subject.other	product safety	en
dc.subject.other	pulsed field gel electrophoresis	en
dc.subject.other	Cheese	en
dc.subject.other	Colony Count, Microbial	en
dc.subject.other	Consumer Product Safety	en
dc.subject.other	Electrophoresis, Gel, Pulsed-Field	en
dc.subject.other	Fermentation	en
dc.subject.other	Food Contamination	en
dc.subject.other	Food Handling	en
dc.subject.other	Food Microbiology	en
dc.subject.other	Humans	en
dc.subject.other	Hydrogen-Ion Concentration	en
dc.subject.other	Listeria monocytogenes	en
dc.subject.other	Water	en
dc.subject.other	Listeria monocytogenes	en
dc.title	Effect of pH and water activity on the growth limits of Listeria monocytogenes in a cheese matrix at two contamination levels	en
heal.type	journalArticle	en
heal.identifier.primary	10.4315/0362-028X.JFP-11-102	en
heal.publicationDate	2011	en
heal.abstract	Listeria monocytogenes can proliferate at the beginning of cheesemaking as the conditions favor growth. The objective of this study was to establish the growth limits of L. monocytogenes in a cheese matrix, in case of potential contamination of the milk prior to cheese manufacture. A semisoft laboratory scale model cheese system was made at different initial pH and water activity (a w) levels with a mix of two strains of L. monocytogenes. A factorial design of five pH values (5.6 to 6.5), four a w values (0.938 to 0.96), and two L. monocytogenes inoculation levels (1 to 20 CFU/ml and 500 to 1,000 CFU/ml) was carried out. Each combination was evaluated in six independent replicates. In order to determine if there was a dominant strain, isolated colonies from the cheeses were analyzed by pulsed-field gel electrophoresis. The data relating to growth initiation were fitted to a logistic regression model. The a w of milk influenced the probability of growth initiation of L. monocytogenes at both low and high contamination levels. The pH, at the concentrations tested, had a lower effect on the probability of growth initiation. At pH 6.5 and a w of 0.99 for low contamination levels and pH 6.5 and a w of 0.97 for high contamination levels, increases in population of up to 4 and 2 log were observed at low and high contamination levels, respectively. This shows that if conditions are favorable for growth initiation at the early stages of the cheesemaking process, contamination of milk, even with low numbers, could lead to L. monocytogenes populations that exceed the European Union's microbiological limit of 100 CFU/g of cheese. Copyright © International Association for Food Protection.	en
heal.journalName	Journal of Food Protection	en
dc.identifier.issue	11	en
dc.identifier.volume	74	en
dc.identifier.doi	10.4315/0362-028X.JFP-11-102	en
dc.identifier.spage	1805	en
dc.identifier.epage	1813	en