Abstract
Different inactivation kinetics data have been used to predict the number of survivors exposed to a heat treatment and, in consequence, to design thermal processes for the food industry. In this work, spores of an acidophilic strain of Bacillus subtilis were heated under isothermal and non-isothermal conditions. Experimental results obtained after isothermal treatments were analysed using the classical two-step linear regression procedure and a one-step non-linear regression method. Data obtained after non-isothermal treatments were analysed using a one-step, non-linear procedure. Kinetic parameters obtained from isothermal heating were close, either using the two-step linear regression (D 100=6.5 min) or the one-step non-linear regression (D 100=6.3 min), although the second method gave smaller 95% confidence intervals. The z values derived from non-isothermal heating were higher than those obtained in isothermal conditions (z=9.3 °C for non-isothermal heating at 1 °C/min versus z=7.7 °C for isothermal heating one step non-linear regression). Results were validated with experimental data obtained after different heat treatments, consisting of a phase of temperature increase at a fixed rate, followed by a holding phase. Non-isothermal methods predicted accurately the number of survivors after the heating ramp, while isothermal methods were more accurate for the holding phase of the treatment. When a temperature profile of a typical heat treatment process applied in the food industry was simulated, all predictions were on the safe side.
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This research was financially supported by the Ministerio de Ciencia y Tecnología of the Spanish Government through the Project AGL-2000-0494.
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Conesa, R., Periago, P.M., Esnoz, A. et al. Prediction of Bacillus subtilis spore survival after a combined non-isothermal-isothermal heat treatment. Eur Food Res Technol 217, 319–324 (2003). https://doi.org/10.1007/s00217-003-0749-5
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DOI: https://doi.org/10.1007/s00217-003-0749-5