Thickness and compositional effects on surface heating rate of bologna during in-package pasteurization

The surface heating rate (γ) and final surface temperature (α) during in-package pasteurization were determined for different thickness levels of 2 types of bologna having different (13 and 18%) fat contents. Three thicknesses (4, 12, and 20 mm), corresponding to 1, 3, and 5 slices of bologna, were vacuum-packaged separately in a clear polymer pouch after placing a thermocouple on the surface. Refrigerated samples were immersed in a water bath set to 1 of 4 predetermined temperatures (60, 70, 80, and 90°C), and time and temperature data were recorded for 10 min. Surface heating rate was fastest in the thinnest (4 mm) and slowest in the thickest (20 mm) samples for all 4 temperatures. Surface heating rate was slower in bologna with the higher fat content compared with the lower fat bologna. Final surface temperature attained after 3 min was lower with increased thickness levels for all temperatures. Thus, meat sample thickness and fat content significantly affect surface heating rate and final surface temperature during in-package pasteurization of bologna

Determining Thermal Inactivation of Escherichia coli O157:H7 in Fresh Compost by Simulating Early Phases of the Composting Process ▿

A three-strain mixture of Escherichia coli O157:H7 was inoculated into fresh dairy compost (ca. 107 CFU/g) with 40 or 50% moisture and was placed in an environmental chamber (ca. 70% humidity) that was programmed to ramp from room temperature to selected composting temperatures in 2 and 5 days to simulate the early composting phase. The surviving E. coli O157:H7 population was analyzed by direct plating and enrichment. Optimal and suboptimal compost mixes, with carbon/nitrogen (C/N) ratios of 25:1 and 16:1, respectively, were compared in this study. In the optimal compost mix, E. coli O157:H7 survived for 72, 48, and 24 h in compost with 40% moisture and for 72, 24, and 24 h with 50% moisture at 50, 55, and 60°C, respectively, following 2 days of come-up time (rate of heating up). However, in the suboptimal compost mix, the pathogen survived for 288, 72, and 48 h in compost with 40% moisture and for 240, 72, 24 h in compost with 50% moisture at the same temperatures, respectively. Pathogen survival was longer, with 5 days of come-up time compared with 2 days of come-up. Overall, E. coli O157:H7 was inactivated faster in the compost with 50% moisture than in the compost with 40% at 55 and 60°C. Both moisture and come-up time were significant factors affecting Weibull model parameters. Our results suggest that slow come-up time at the beginning of composting can extend pathogen survival during composting. Additionally, both the C/N ratio and the initial moisture level in the compost mix affect the rate of pathogen inactivation as well