Expanded models for the non-thermal inactivation of Listeria monocytogenes

Abstract

. 1997. Previously developed four-variable response surface models for describing the effects of temperature, pH/lactic acid, sodium chloride and sodium nitrite on the time to achieve a 4-log, non-thermal inactivation (t4,,) of Listeria monoqytogenes in aerobic, acidic environments were expanded to five-variable models that distinguish the effects of pH and acidulant concentration. A total of 18 new variable combinations were evaluated and the inactivation kinetics data appended onto a consolidation of two data sets from earlier studies. The consolidated data set, which included 3 15 inactivation curves representing 209 unique combinations of the five variables, was analysed by response surface analysis.T h e quadratic model without backward elimination regression was selected for further evaluation. Three additional quadratic models were generated using the concentrations of undissociated lactic and/or nitrous acids as variables in place of percentage lactic acid and sodium nitrite concentration. Comparison of predicted t4,, values against literature values for various food systems indicated that the models provide reasonable initial estimates of the inactivation of L. monocytogenes. The models based on the concentration of undissociated lactic and nitrous acids support the hypothesis that antimicrobial activity is associated with this form of the compounds. Evaluation of several examples suggests that these models may be useful for predicting the equivalent of the compounds' 'minimal inhibitory concentrations' for accelerating inactivation under various conditions.

Acid Resistance of Twelve Strains of Enterobacter sakazakii, and the Impact of Habituating the Cells to an Acidic Environment

“…Despite the fact that there is an extensive body of research on the survival of foodborne bacteria in acidic environments, it is difficult to directly compare the acid resistance of E. sakazakii with that of other pathogens. This reflects the fact that the ability of a microorganism to survive an exposure to an acid environment is dependent on a large number of factors such as pH, acidulant identity, acidulant concentration, temperature, water activity, atmosphere, and the presence of other inhibitory compounds (Buchanan and others 1994, 1997; Buchanan and Golden 1995; Buchanan and Edelson 1999). Investigators have employed an array of pH values, acidulants, incubation temperatures, and water activities, making it difficult to quantitatively compare reported acid resistances.…”

MODELING THE BEHAVIOR OF LISTERIA MONOCYTOGENES IN pH‐MODIFIED CHICKEN SALAD DURING COLD STORAGE AND TEMPERATURE ABUSE CONDITIONS

“…Xiong et al . (1999b) also proposed a model based on the inactivation model of Buchanan et al . (1997a) that could describe a shoulder region followed by log‐linear inactivation.…”

“…The survival of L. monocytogenes under varied environmental conditions has been the focus of several predictive modeling studies. Some conditions of particular interest include the effects of varied cold storage temperature (Saguy 1992), the addition of NaNO 2 and NaCl (Buchanan et al . 1997a) and modified pH by the addition of lactic and/or acetic acid (Buchanan et al .…”

“…The implementation of the guidelines may be instrumental in preventing outbreaks of foodborne listeriosis. Therefore, the objective of this research was to compare the microbial behavior predictions of a broth‐based model for L. monocytogenes reported by Buchanan et al . (1997a) to that of a nonlinear model.…”

Safety assessment of the maximum permitted levels of L. monocytogenes in food according to health risk criteria

“…More than 20% of the population is considered to fall in the high risk group for Listeria monocytogenes [44,45]. Healthy children and immune-competent adults have a low risk of severe Listeria monocytogenes.…”