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RESEARCH PRODUCT

Experimental Evaluation of a New Thermal Process for Microorganisms Inactivation

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A new thermal process for the inactivation of microorganisms in beverages has been studied and is presented in this paper. The treatment, not yet studied in the scientific literature, mainly consists of a thermal shock characterized by temperature increases up to 30°C/s, with final temperatures up to 65°C. This study presents the first experimental results obtained by the application of the new thermal treatment, with different combinations of the process parameters (rate of temperature rise, final temperature and holding time), on separate suspensions of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Listeria innocua and Candida albicans. The required rapid temperature increase has been performed by means of a properly designed test bench. The treatment proved to be effective against all the microorganisms tested, obtaining a load reduction greater than 5 Log units. Compared with the commonly employed thermal treatments for microorganisms inactivation, this new process is characterized by a very interesting combination of a short duration (few seconds) and a low final temperature, which makes it particularly attractive for the application in the beverage industry. Practical Applications Nowadays, most liquid foods, such as beverages, milk, fruit and vegetables juices, are pasteurized by high-temperature/short-time treatments and then bottled or packaged under rigidly maintained sterile conditions. Thanks to the very short duration of this new treatment and to its relatively low maximum temperature (65°C), which does not endanger the plastic materials commonly employed for bottles packaging, its online application in the filling process could be conveniently considered: this would avoid the use of an aseptic environment and the risk of the post-processing contamination. Moreover, a final temperature as low as 65°C would also preserve the sensorial and nutritional features of the beverage, which are usually deteriorated by the common high temperature treatments, and would be in agreement with the present-day energy-saving policy.