Ultrasound‐steam combination process for microbial decontamination and heat transfer enhancement

Abstract

Steam is by far the most effective heating medium used in commercial thermal processing applications. However, for rapid short time direct heating of food products it poses some serious difficulties because of the presence of air along the surface and internal tissues of the food products interferes with the heat transfer mechanism and slows down the effective heating of the surface. Addition of an ultrasound environment to steam can assist in removing this surface barrier and promote better heat transfer. The objective of this research was to evaluate the suitability of ultrasound—steam combination heating for (a) microbial decontamination and (b) enhancing heat transfer. It was demonstrated that short‐time (15 s) combined ultrasound—steam heating could result in more than five logarithmic cycle destruction of Escherichia coli population on carrot surfaces. Secondly, for longer time heating, the combination heat treatment was more efficient than steam alone for enhancing heat transfer rates contributing to achieve a lower heating rate index, higher temperatures and higher process lethality values. Practical Applications Surface contamination of fruits, vegetables, and meats present a serious problem with respect to public health safety and their marketability. Many techniques have been employed for microbial decontamination of food contact surfaces only with limited success. New methods are always evolving to improve the process efficiency without impairing the product quality. Physical methods are gaining more popularity than chemicals due to consumer concerns for chemical additives. While steam and sound have been independently used successfully for various food processing applications, their combination has not been widely tried either to improve the efficacy of surface decontamination or improved heat transfer. The main focus of this study is to review and demonstrate the success ultrasound‐steam combination process.

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