Publications by Year: 2005

This study was conducted to evaluate small-scale hot-water postpackaging pasteurization (PPP) as a postlethality (post-cooking) treatment for Listeria monocytogenes on ready-to-eat beef snack sticks and natural-casing wieners. Using a commercially available plastic packaging film specifically designed for PPP applications and 2.8 liters of boiling water (100 degrees C) in a sauce pan on a hot plate, an average reduction in L. monocytogenes numbers of > or = 2 log units was obtained using heating times of 1.0 min for individually packaged beef snack sticks (three brands) and 4.0 min for packages of four sticks (two brands) and seven sticks (three brands). Average product surface temperatures, measured as soon as possible after PPP and opening the package, were 47 to 51.5, 58 to 61.5, and 58.5 to 61 degrees C for the beef snack sticks packages of one, four, and seven sticks per package, respectively. A treatment of 7.0 min for packages of four natural-casing wieners (three brands) achieved L. monocytogenes reductions of > or = 1.0 log unit and average product surface temperature of 60.5 to 63.5 degrees C. Cooked-out fat and moisture resulting from tested treatments ranged from 0.2 to 1.1% by weight for beef snack sticks and from 0.4 to 1.2% by weight for natural-casing wieners. For natural-casing wieners, PPP had no detrimental effect on overall product desirability to consumers; results suggested that PPP may significantly enhance appearance of this product. However, for beef snack sticks the cooking out of fat and moisture during PPP had a significant negative effect on consumer opinions of product appearance.

Food regulatory agencies advise against thawing frozen meat and poultry at room temperature. In this study, whole chickens (1,670 g) and ground beef (453 and 1,359 g) were inoculated with Salmonella serovars, Escherichia coli O157:H7, and Staphylococcus aureus on the surface (all products) and in the center (ground beef). After freezing at -20 degrees C for 24 h, products were thawed at 22 or 30 degrees C for 9 h. Pathogen growth was predicted using product time and temperature data and growth values from the U.S. Department of Agriculture Agricultural Research Service Pathogen Modeling Program 7.0 predictive models of pathogen growth. No pathogen growth was predicted for whole chicken or 1,359 g of ground beef thawed at 30 degrees C or 453 g of ground beef thawed at 22 degrees C. Growth (< or = 5 generations) was predicted for 453 g of ground beef at 30 degrees C. Inoculation study data corroborated the predictions. No growth occurred on whole chickens or 1,359-g portions of ground beef thawed at 30 degrees C for 9 h. Pathogen numbers increased an average of 0.2 to 0.5 log on the surface of 453-g ground beef portions thawed for 9 h at 22 or 30 degrees C. Our results suggest that thawing > or = 1,670 g of whole chicken at < or = 30 degrees C for < or = 9 h and thawing >453 g ground beef portions at < or = 22 degrees C for < or = 9 h are not particularly hazardous practices. Thawing smaller portions at higher temperatures and/or for longer times cannot be recommended, however. Use of values derived from the Pathogen Modeling Program 7.0 model provided realistic predictions of pathogen growth during thawing of frozen ground beef and chicken.