Resumen de Efficacy of Combined Sous Vide‐Microwave Cooking for Foodborne Pathogen Inactivation in Ready‐to‐Eat Chicory Stems

Massimiliano Renna, Maria Gonnella, Silvia Candia, Francesco Serio, Federico Baruzzi

• There is a variety of different food processing methods, which can be used to prepare ready‐to‐eat foods. However, the need to preserve the freshness and nutritional qualities leads to the application of mild technologies which may be insufficient to inactivate microbial pathogens. In this work, fresh chicory stems were packed under a vacuum in films, which were transparent to microwaves. These were then exposed to microwaves for different periods of time. The application of sous videmicrowave cooking (SV‐MW, 900 W, 2450 MHz), controlled naturally occurring mesophilic aerobic bacteria, yeasts and molds for up to 30 d when vacuum‐packed vegetables were stored at 4 °C. In addition, the process lethality of the SV‐MW 90 s cooking was experimentally validated. This treatment led to 6.07 ± 0.7 and 4.92 ± 0.65 log cfu/g reduction of Escherichia coliand Listeria monocytogenesinoculated over the chicory stems (100 g), respectively. With an initial load of 9 log cfu/g for both pathogens, less than 10 cfu/g of surviving cells were found after 90 s cooking. This shows that short‐time microwave cooking can be used to effectively pasteurize vacuum‐packed chicory stems, achieving >5 log cfu/g reduction of E. coliand L. monocytogenes. The combined SV‐MW approach reported here allows a reduction of time needed for the treatment. In addition to this, a reduction of energy consumption compared with conventional SVcooking when it takes place in hot water. The shorter treatment time and the safety level reached by SV‐MW 90 s cooking opens the possibility for an industrial scale up.