Ultrasound enhanced steam and hot water pasteurization of pineapple and apple slices in flexible pouches

This research investigated the ultrasound (U) enhancement of steam (S, SU), steam/air (SA, SAU) and hot water (W, WU) processes for the pasteurization of high acid foods in flexible pouches. A specially designed ultrasound setup was developed to process cut pineapples and apples in sugar solution that were pre-packaged in flexible retort pouches with steam and ultrasound combination treatments. An ultrasonic hot water bath was used to process these pre-packaged products under water and ultrasound combinations. All pasteurization techniques were designed to deliver a target lethality (F90 °C-10 min) through heat penetration testing and were compared for reduction in process time and improvement in product quality. Compared S, SA and W, the ultrasound assisted processes, SU, SAU, and WU, resulted in significantly reduced processing times presumably due to the induced ultrasound agitation and helped to improve the product quality. The resulting impact of these processes on quality of apple and pineapple slices depended on the specific process and quality indices, but the quality parameters were considerably better for the ultrasound assisted processes. Hence, ultrasound pasteurization was recommended as another viable technique for agitation processing of foods in flexible containers.