title: Modeling the Effect of Temperature and Water Activity on the Thermal Resistance of Salmonella Enteritidis PT 30 in Wheat Flour.
abstract: Salmonella continues to be a problem associated with low-moisture foods, particularly given enhanced thermal resistance at lower water activity (aw). However, there is a scarcity of thermal inactivation models accounting for the effect of aw. The objective of this study was to test multiple secondary models for the effect of product (wheat flour) awon Salmonella enterica Enteritidis phage type 30 thermal resistance. A full-factorial experimental design included three temperatures (75, 80, and 85°C) and four awvalues (~0.30, 0.45, 0.60, and 0.70). Prior to isothermal treatment, sample awwas achieved by equilibrating samples in a humidity-controlled conditioning chamber. Two primary models (log linear and Weibull type) and three secondary models (second-order response surface, modified Bigelow type, and combined effects) were evaluated using the corrected Akaike information criterion and root mean squared errors. Statistical analyses of the primary models favored the log-linear model. Incorporating the three secondary models into the log-linear primary model yielded root mean squared errors of 2.1, 0.78, and 0.96 log CFU/g and corrected Akaike information criterion values of 460, -145, and -19 for the response surface, modified Bigelow, and combined-effects models, respectively. The modified Bigelow-type model, which exponentially scaled both temperature and aweffects on thermal inactivation rates, predicted Salmonella lethality significantly better (P < 0.05) than did the other secondary models examined. Overall, awis a critical factor affecting thermal inactivation of Salmonella in low-moisture products and should be appropriately included in thermal inactivation models for these types of systems.
authors.affiliation: Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Danielle F
authors.initials: DF
authors.lastname: Smith
authors.affiliation: Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Hildebrandt
authors.affiliation: Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Kaitlyn E
authors.initials: KE
authors.lastname: Casulli
authors.affiliation: Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824, USA.|Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Kirk D
authors.initials: KD
authors.lastname: Dolan
authors.affiliation: Department of Biosystems and Agricultural Engineering, Michigan State University, East Lansing, Michigan 48824, USA.|Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Bradley P
authors.initials: BP
authors.lastname: Marks
mesh_terms: D015169:Colony Count, Microbial; D005433:Flour; D005506:Food Contamination; D005511:Food Handling; D005516:Food Microbiology; D012475:Salmonella; D012477:Salmonella enteritidis; D013696:Temperature; D014908:Triticum; D014867:Water
chemical_list: D014867:Water
keywords: Lethality; Moisture; Predictive microbiology; Secondary model; Water activity