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State of the art of nonthermal and thermal processing for inactivation of micro-organisms

Despite the constant development of novel thermal and nonthermal technologies, knowledge on the mechanisms of microbial inactivation is still very limited.Technologies such as high pressure, ultraviolet light, pulsed light, ozone, powerultrasound and cold plasma (advanced oxidation processes) have shownpromising results for inactivation of micro-organisms. The efficacy of inactivationis greatly enhanced by combination of conventional (thermal) with nonthermal, or nonthermal with another nonthermal technique. The key advantages offered bynonthermal processes in combination with sublethal mild temperature (<60°C)can inactivate micro-organisms synergistically. Microbial cells, when subjected toenvironmental stress, can be either injured or killed. In some cases, cells arebelieved to be inactivated, but may only be sublethally injured leading to theirrecovery or, if the injury is lethal, to cell death. It is of major concern when micro-organisms adapt to stress during processing. If the cells adapt to a certain stress, itis associated with enhanced protection against other subsequent stresses. One ofthe most striking problems during inactivation of micro-organisms is spores.They are the most resistant form of microbial cells and relatively difficult toinactivate by common inactivation techniques, including heat sterilization, radiation, oxidizing agents and various chemicals. Various novel nonthermalprocessing technologies, alone or in combination, have shown potential forvegetative cells and spores inactivation. Predictive microbiology can be used tofocus on the quantitative description of the microbial behaviour in food products, for a given set of environmental conditions.

cell injury, modelling, non-thermal processes, stress response, thermal processes

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