Ohmic heating in fruit and vegetable processing: Quality characteristics, enzyme inactivation, challenges and prospective

Abstract

Ohmic heating (OH), an alternative technique to conventional heating method, is a process in which food acts as an electrical resistor and converts electrical energy into thermal energy following the Joule's law. OH has been widely applied in the processing of fruits and vegetables due to its fast and volumetric heating mode. This review focuses on the effects of OH on the important enzymes (polyphenoloxidase, peroxidase and pectin methylesterase) in fruits and vegetables and the quality characteristics (electrical conductivity, color, pH, sensory quality and bioactive compounds) of fruits and vegetables. Meanwhile, the mechanisms behind the effects are also elucidated. At last, an overview of the application of OH in fruit and vegetable processing was performed in this work, including concentration, blanching, thawing, extraction and pasteurization. The literature review suggests that OH shows enhanced inactivation rate on several important enzymes in fruits and vegetables owing to the presence of non-thermal effect. Due to the rapid and uniform heating mode, OH processing has a better performance in retaining the natural color, pH, sensory quality and bioactive compounds (ascorbic acid, phenolic compounds, anthocyanins, carotenoids, chlorophyll and betalains) compared to conventional heating approaches. However, the challenge of electrochemical reactions needs to be addressed before industrial scale application. • Non-thermal effect of OH evidently affects enzymes, color and bioactive compounds. • OH enhanced the inactivation effect on vital enzymes in fruits and vegetables. • OH retaining better color, pH and bioactive compounds compared to CH. • Electrochemical reactions need to be addressed before industrial scale application.