29G-27 |
Validation of the efficacy of non-isothermal pasteurisation treatments based on data from isothermal heat treatments |
M. HASSANI1, P. Mañas, J. Raso-Pueyo3, S. Condón, and R. Pagán. (1) Tecnología de Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, C/ Miguel Servet, 177, Zaragoza, 50013, Spain, (2) Tecnología de los Alimentos, Facultad de Veterinaria. Universidad de Zaragoza, Zaragoza, 50013, Spain Food pasteurization pretends the destruction of all microorganisms potentially dangerous to human health. For this purpose, heat treatments have been calculated for different foods depending on their characteristics and usual microbial contamination. These calculations have been carried out assuming an exponential relationship between treatment temperature and heat resistance. However, in food products requiring long heating lag phases, such as “sous-vide” products, minimally processed refrigerated food and precooked products, bacterial pathogens might respond to sublethal temperatures, adapting to heat, and increasing their heat resistance. As a consequence, it has been suggested that the risk of some of these microorganisms surviving heat treatment would increase. The objective was to evaluate whether heat resistance data obtained from isothermal treatments allow to estimate survivors of Listeria monocytogenes after a non-isothermal heat treatment. Heat resistance of Listeria monocytogenes was carried out in a thermorresistometer under isothermal (52-62ºC) and anisothermal (heating rate: 2ºC/min; final temperature: 60ºC) conditions. Triptic Soy Broth adjusted at pH 7.4, 5.5 and 4 was used as treatment media. Survival curves were fitted by a model based on the Weibull distribution. A differential equation was used to estimate survival curves under non-isothermal conditions. Listeria monocytogenes was more heat resistant at pH 7.4 than at pH 5.5 or 4. Time to inactivate 5 log cycles of cells at 60ºC in pH 7.4, 5.5 and 4 was 2.45, 0.75 and 0.55 min respectively. A linear relationship was observed between the scale parameter of the Weibull model and the treatment temperature. Estimations of survival curves under non-isothermal treatments obtained from parameters of isothermal treatments fitted to experimental values at any pH investigated. Survival curves of Listeria monocytogenes under non-isothermal treatments have been accurately estimated from heat resistance parameters obtained under isothermal conditions.
Session 29G, Food Microbiology: General
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