Effect of Prior Growth Conditions on the Thermal Inactivation of 13 Strains of Listeria monocytogenes in Two Heating Menstrua
Abstract:The thermal tolerance of 13 Listeria monocytogenes strains was tested using a submerged heating coil apparatus. The strains were grown individually for 18 h at 37°C in acidogenic tryptic soy broth (without dextrose) supplemented with 1% glucose and 1% glutamine (TSB+G) or nonacidogenic tryptic soy broth supplemented with 1% glutamine but containing no glucose (dextrose) (TSB-G). The former medium results in cells induced for pH-dependent, stationary-phase acid resistance, whereas the latter medium allows L. monocytogenes to grow to high numbers in the absence of glucose, yielding cells that are not induced for pH-dependent, stationary-phase acid resistance. The average final pH values of the 18-h TSB+G and the TSB-G cultures were 4.7 and 6.7, respectively. The cells grown in the acid resistance–inducing and non–acid resistance–inducing media were then tested in two heating menstrua that consisted of brain heart infusion broth adjusted to pH 3.0 and water activity (aw) of 0.987 or pH 7.0 and aw 0.970. In 14 of the 26 menstruum-strain combinations tested, the acid resistance–induced strains were more heat resistant then the equivalent noninduced cultures. No difference in the pattern of thermal resistance in response to induction of acid resistance was apparent among the different serovars tested. The results suggest that the ability of prior induction of acid resistance to enhance thermal resistance can vary substantially among L. monocytogenes strains.
Document Type: Short Communication
Affiliations: 1: Department of Health and Human Services, Food and Drug Administration, Center for Food Safety and Applied Nutrition, College Park, Maryland 20740, USA 2: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, USA
Publication date: January 1, 2005
- IAFP Members with personal subscriptions to JFP Online: To access full-text JFP or JMFT articles, you must sign-in in the upper-right corner using your Ingenta sign-in details (your IAFP Member Login does not apply to this website). The Journal of Food Protection (JFP) is a refereed monthly publication. Each issue contains scientific research and authoritative review articles reporting on a variety of topics in food science pertaining to food safety and quality. The Journal is internationally recognized as the leading publication in the field of food microbiology with a readership exceeding 11,000 scientists from 70 countries. The Journal of Food Protection is indexed in Index Medicus, Current Contents, BIOSIS, PubMed, Medline, and many others.
Print and online subscriptions are available to IAFP Members and institutional subscribers. IAFP Members with a subscription to JFP Online will have access to all available JFP and JMFT content. Online visitors who are not IAFP Members or journal subscribers will be charged on a pay-per-view basis. Membership and subscription information is available at www.foodprotection.org.
- Information for Authors
- Submit a Paper
- Subscribe to this Title
- Membership Information
- Information for Advertisers
- ingentaconnect is not responsible for the content or availability of external websites