Authors: D.S. Head And S. Cenkowski
Identifier: C0908
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Published in: CBE Journal » CBE Journal Volume 52 (2010)

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Description: Spores of Geobacillus stearothermophilus at two inoculum levels [3 and 6 log colonyforming units per gram (cfu/g)] were challenged with superheated steam (SS) at a velocity of 0.35 m/s and temperatures of 130, 145,160, and 175 C. A tendency of tailing was observed in  the survivor curves [plots of survival ratio, log (N/No), against processing time] as a monotonic upward concavity. Therefore,non-linear regression models, the Weibull and Kamau models, instead of the traditional   first-order kinetics model were used to describe the survivor curves. The Weibull model was successfully fitted to all survivor curves obtained in this study, whereas the Kamaumodel agreed only for some. A high  correlation between the predicted and observed values of spore survival ratio were obtained for the SS treatment in the range of 145-175 C at both inoculum levels, and for SS treatment at 1308C at low inoculum level. The Weibull model was expanded by describing its parameters (a, b) as a function of SS temperature for the range of 130 175 C. This allowed accurate predictions ofthe spore survival ratio based on the SS temperature and processing time only (with the exception of predictions for spores at high inoculum level challenged with SS at 130 C).  Hence,the Weibull model is recommended for describing and modelling of inactivation of G.stearothermophilus spores in SS at higher  temperatures (145-175 C).

Keywords: modelling, spores, inactivation, geobacillus stearothermophilus.
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Date: 2010-09-16
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Publication type: Journal
Coverage: Canada
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