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Applied and Environmental Microbiology, April 2009, p. 1885-1891, Vol. 75, No. 7
0099-2240/09/$08.00+0     doi:10.1128/AEM.02283-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Prediction of a Required Log Reduction with Probability for Enterobacter sakazakii during High-Pressure Processing, Using a Survival/Death Interface Model{triangledown}

Shige Koseki,* Maki Matsubara, and Kazutaka Yamamoto

National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan

Received 5 October 2008/ Accepted 2 February 2009

A probabilistic model for predicting Enterobacter sakazakii inactivation in trypticase soy broth (TSB) and infant formula (IF) by high-pressure processing was developed. The modeling procedure is based on a previous model (S. Koseki and K. Yamamoto, Int. J. Food Microbiol. 116:136-143, 2007) that describes the probability of death of bacteria. The model developed in this study consists of a total of 300 combinations of pressure (400, 450, 500, 550, or 600 MPa), pressure-holding time (1, 3, 5, 10, or 20 min), temperature (25 or 40°C), inoculum level (3, 5, or 7 log10 CFU/ml), and medium (TSB or IF), with each combination tested in triplicate. For each replicate response of E. sakazakii, survival and death were scored with values of 0 and 1, respectively. Data were fitted to a logistic regression model in which the medium was treated as a dummy variable. The model predicted that the required pressure-holding times at 500 MPa for a 5-log reduction in IF with 90% achievement probability were 26.3 and 7.9 min at 25 and 40°C, respectively. The probabilities of achieving 5-log reductions in TSB and IF by treatment with 400 MPa at 25°C for 10 min were 92 and 3%, respectively. The model enabled the identification of a minimum processing condition for a required log reduction, regardless of the underlying inactivation kinetics pattern. Simultaneously, the probability of an inactivation effect under the predicted processing condition was also provided by taking into account the environmental factors mentioned above.

* Corresponding author. Mailing address: 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan. Phone: 81-29-838-7152. Fax: 81-29-838-8122. E-mail: koseki{at}affrc.go.jp

{triangledown} Published ahead of print on 6 February 2009.

Applied and Environmental Microbiology, April 2009, p. 1885-1891, Vol. 75, No. 7
0099-2240/09/$08.00+0     doi:10.1128/AEM.02283-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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