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RESEARCH PRODUCT

Extended Validation of Dynamic Irreversible Thermoporation: A Novel Thermal Process for Microbial Inactivation

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A novel thermal treatment for microorganism inactivation, characterized by a very rapid temperature increase (up to 30°C/s) and a low final temperature (up to 65°C) maintained for a relatively short holding time, has been recently presented and tested by the authors, showing microbial load reduction greater than 5 log units against several common bacteria and yeasts. With the aim of extending the possible use of the new thermal treatment to a wider microorganisms class, in this work the dynamic irreversible thermoporation (DIT) treatment was further tested on a well-known thermoresistant strain, the Enterococcus hirae: The results of these new experimental tests confirmed the reliability of the process, which allowed to reach the 5 log microbial reduction once the adequate holding time was employed. The comparison with simple immersion in a thermostatic bath, where the very slow heating process with 0.3°C/s has been performed, confirmed the crucial role of the thermal shock for the success of the treatment. The inactivation kinetics of E. hirae in isothermal conditions immediately after the application of thermal shock has also been studied. Finally, the morphological analysis performed by using a scanning electron microscope clearly revealed the rupture of the cell membrane, leading to identification of the process called dynamic irreversible thermoporation (DIT). Practical Applications The main features of the dynamic irreversible thermoporation (DIT) process produce two major advantages with respect to the traditional heat treatments commonly employed for beverages: one perfectly agrees with production economics principles, while the other concerns the quality of the product. First, the DIT process can be implemented directly on bottled products because its low maximum temperature of 65°C is compatible with the plastic materials usually employed for sealed beverages: Its online application in the filling process could hence be conveniently considered, thus avoiding both the use of an expensive aseptic environment and the risk of post-processing contamination. Second, by using such a low final temperature, the thermal degradation of the food components is avoided, with consequent preservation of the sensory and nutritional quality of the fresh-like food products.