Lag-phase duration (LPD) and growth rate (GR) values were calculated from experimental data obtained using a previously described protocol (S. C. Ingham, M. A. Fanslau, G. M. Burnham, B. H. Ingham, J. P. Norback, and D. W. Schaffner, J. Food Prot. 70:1445-1456, 2007). These values were used to develop an interval accumulation-based tool designated THERM (temperature history evaluation for raw meats) for predicting growth or no growth of Salmonella serovars, Escherichia coli O157:H7, and Staphylococcus aureus in temperature-abused raw sausage. Data (time-temperature and pathogen log CFU per gram) were obtained from six inoculation experiments with Salmonella, E. coli O157:H7, and S. aureus in three raw pork sausage products stored under different temperature abuse conditions. The time-temperature history from each experiment was entered into THERM to predict pathogen growth. Predicted and experimental results were described as growth (> 0.3 log increase in CFU) or no growth (< or = 0.3 log increase in CFU) and compared. The THERM tool accurately predicted growth or no growth for all 18 pathogen-experiment combinations. When compared with the observed changes in log CFU values for the nine pathogen-experiment combinations in which pathogens grew, the predicted changes in log CFU values were within 0.3 log CFU for three combinations, exceeded observed values by 0.4 to 1.5 log CFU in four combinations, and were 1.2 to 1.4 log CFU lower in two combinations. The THERM tool approach appears to be useful for predicting pathogen growth versus no growth in raw sausage during temperature abuse, although further development and testing are warranted.
U.S. Department of Agriculture (USDA) composition-based labeling standards for various ready-to-eat (RTE) meat products typically specify maximum product pH and/or moisture:protein ratio and less often maximum water activity (a(w)). Compliance with these standards often has been regarded as proof of shelf stability. However, the USDA now requires additional proof, e.g., challenge study results, of shelf stability. The pathogen most likely to grow on vacuum-packaged, reduced-moisture products is Staphylococcus aureus. Therefore, vacuum-packaged RTE products that do not support S. aureus growth at room temperature could be considered shelf stable. We developed mathematical equations for predicting whether S. aureus would grow under such conditions. Twenty-four commercial RTE meat products and 10 intentionally misprocessed products (insufficient drying, fermentation, and/or salt) were inoculated with a five-strain cocktail of S. aureus, vacuum packaged, and stored at 21 degrees C. Initial, 7-day, and 28-day S. aureus counts were recorded. Product pH, a(w), moisture:protein ratio, and percentage of water-phase salt (%WPS) also were determined. S. aureus grew only in the intentionally misprocessed products and in some commercial products labeled "keep refrigerated." Using bias reduction logistic regression data analysis, the probability of S. aureus growth (Pr) could be predicted by either of two equations. The first was based on pH and a(w) values: Pr = exp[-59.36 + (5.75 x pH) + (28.73 x a(w))]/{1 + [exp(-59.36 + (5.75 x pH) + (28.73 x a(w))]}. The second was based on pH and %WPS: Pr = exp[-26.93 + (5.38 x pH) + (-0.61 x %WPS)]/{1 + exp[-26.93 + (5.38 x pH) + (-0.61 x %WPS)]}. These equations accounted for observed S. aureus growth-no growth results and will be a useful tool for evaluating the shelf stability of RTE meats.
The objective of this study was to determine if a correlation exists between standard plate count (SPC) and somatic cell count (SCC) monthly reported results for Wisconsin dairy producers. Such a correlation may indicate that Wisconsin producers effectively controlling sanitation and milk temperature (reflected in low SPC) also have implemented good herd health management practices (reflected in low SCC). The SPC and SCC results for all grade A and B dairy producers who submitted results to the Wisconsin Department of Agriculture, Trade, and Consumer Protection, in each month of 2012 were analyzed. Grade A producer SPC results were less dispersed than grade B producer SPC results. Regression analysis showed a highly significant correlation between SPC and SCC, but the R(2) value was very small (0.02-0.03), suggesting that many other factors, besides SCC, influence SPC. Average SCC (across 12 mo) for grade A and B producers decreased with an increase in the number of monthly SPC results (out of 12) that were ≤ 25,000 cfu/mL. A chi-squared test of independence showed that the proportion of monthly SCC results >250,000 cells/mL varied significantly depending on whether the corresponding SPC result was ≤ 25,000 or >25,000 cfu/mL. This significant difference occurred in all months of 2012 for grade A and B producers. The results suggest that a generally consistent level of skill exists across dairy production practices affecting SPC and SCC.
Anecdotal information suggests that some Hispanic consumers may consider US-made Hispanic cheeses as having a general lack of authenticity compared with those made in their countries of origin. To characterize the potential differences, samples of fresh, pasta filata, and aged Hispanic cheeses were acquired from both the United States (total n=39) and countries of origin (total n=30) purchased from Mexico, Central America (Costa Rica and El Salvador), and the Caribbean (Puerto Rico). The proximate composition, microbial counts, melt profile, and sensory characteristics were evaluated and compared in country-of-origin cheeses and the US-made counterparts. The presence of Listeria spp. was confirmed for 1 Mexican aged cheese sample and 6 cheese samples from Central America (3 fresh, 2 pasta filata, and 1 aged). The chemical composition, melt profile, and sensory characteristics of fresh and pasta filata US Hispanic cheeses were not significantly different from their Mexican counterparts. Likewise, the chemical composition and melt profile of US aged Hispanic cheeses was not significantly different from the aged Mexican cheeses, but sensory characteristics varied among all aged cheeses. These results demonstrate the similarities and differences among US fresh, pasta filata, and aged Hispanic cheeses relative to their counterparts made in the countries of origin.
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