Thermal Resistance of Heat-, Cold-, and Starvation-Injured Salmonella in Irradiated Comminuted Turkey
Abstract:To investigate the effects of sublethal stress on Salmonella thermal inactivation kinetics, an eight-strain Salmonella cocktail was subjected to heat shock (30 min at 54°C), cold shock (2 h at 4°C), and starvation stress (10 days in phosphate buffer at 4°C), harvested by centrifugation, and inoculated into irradiated comminuted turkey. Immediately after stressing, the Salmonella cocktails contained 89.1% heat-injured, 44.7% cold-injured, and 67.7% starvation-injured cells, as determined by plating on selective and nonselective media. D 60°C-values for the heat-shocked cocktail (0.64 min on Trypticase soy agar containing 0.6% yeast extract [TSAYE], 0.35 min on xylose lysine desoxycholate [XLD] agar) were higher (P < 0.05) than those for the unshocked control (0.41 min on TSAYE, 0.17 min on XLD), whereas D 60°C-values for the cold-shocked cocktail (0.38 min on TSAYE, 0.17 min on XLD) were not significantly different from those for the control. Starved cells had the sameD 60°C-value on TSAYE as did the unshocked cocktail, but the D 60°C-value on XLD was significantly lower (0.14 min). Although starvation and cold shock were not thermally protective, heat shock increased thermal resistance, indicating that product history and the physiological state of the Salmonella cells should be considered when developing and validating thermal processes. D 60°C-values observed on selective media were significantly lower than those observed on nonselective media for all stress treatments and for the control. Therefore, nonselective culture media should be used to assess the response of microorganisms to a thermal challenge when developing performance standards for lethality.
Document Type: Research Article
Affiliations: 1: Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824, USA 2: Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824, USA
Publication date: May 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
- Ingenta Connect is not responsible for the content or availability of external websites