|HILDEBRANDT, BRANDLEY - Michigan State University|
|MARKS, BRADLEY - Michigan State University|
|HALL, NICOLE - Michigan State University|
|RYSER, ELLIOT - Michigan State University|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2016
Publication Date: 7/12/2016
Citation: Hildebrandt, B., Juneja, V.K., Osoria, M., Marks, B.P., Hall, N.O., Ryser, E.T. 2016. Cross-laboratory comparative study of the impact of experimental and regression methodologies on salmonella thermal inactivation parameters in ground beef. Journal of Food Protection. 79(7):1097-1106. doi: 10.4315/0362-028X.JFP-15-496.
Interpretive Summary: Researchers have reported different thermal death time values for a deadly pathogen, Salmonella, in beef. We collected data for heat inactivation of the pathogen in two independent laboratories using two different methods. We found a significant difference between the characteristics and quality of data yielded by the separate laboratory methodologies. A large and typically unknown uncertainty was noted when data from multiple studies across laboratories were combined. This observation emphasizes the need for regulatory agencies and food industry to consider the influence of laboratory methodologies and the resulting limitations of the industrial thermal lethality processes, and will assist them to standardize the laboratory methodologies.
Technical Abstract: Isothermal inactivation studies are commonly used to quantify thermal inactivation kinetics of bacteria. Meta-analyses and comparisons utilizing results from multiple sources have revealed large variations in reported inactivation parameters for Salmonella, even in similar food materials. Different laboratory or regression methodologies likely are the source of methodology-specific artifacts influencing the estimated thermal parameters; however, such effects have not been quantified. The objective of this study was to evaluate the effects of laboratory and regression methodologies on thermal inactivation data generation, interpretation, modeling, and inherent error, based on data generated in two independent laboratories. The overall design consisted of a cross-laboratory comparison using two independent laboratories (MSU and ERRC laboratories), both conducting isothermal Salmonella inactivation studies (55, 60, 62 degrees C) in ground beef, and each using two methodologies utilized and reported in prior studies. Two primary models (log-linear and Weibull) with one secondary model (modified Bigelow) were fitted to the resultant data using three regression methodologies (two two-step regressions and a one-step regression). Results indicated that laboratory methodology impacted the estimated D (60 degrees C) and z-values (a = 0.05), with the ERRC methodology yielding parameter estimates about 25% larger than the MSU methodology, regardless of the laboratory. Regression methodology also impacted model and parameter error estimates. Two-step regressions yielded RMSE values on average 40% larger than the one-step regressions. The Akaike Information Criterion indicated the Weibull as the more correct model in most cases; however, caution should be used to confirm model robustness in application to real-world data. Overall, the results suggest that laboratory and regression methodologies have a large influence on resultant data and the subsequent estimation of thermal resistance parameters.