Radiofrequency inactivation of oxidative food enzymes in model systems and apple derivatives

The effect of increasing radiofrequency (RF) electric fields on the activity of oxidative enzymes was studied in model systems and food. In particular, the mechanisms of enzyme inactivation by RF treatments were studied on polyphenoloxidase (PPO) and lipoxygenase (LOX) model systems. RF treatments efficiently inactivated both enzymes, although PPO was more sensitive to an increase in the RF electric field. RF efficacy was attributed to the generated thermal effect, while the contribution of the electromagnetic field resulted negligible. Following, the efficacy of RF in blanching vegetables to obtain color stable derivatives was evaluated. To this aim, RF and conventionally water blanched apples were processed to get purees which were analyzed for color, sensory attributes and consumer preference. RF allowed apples to be adequately blanched. In particular, the puree obtained from the RF blanched apples was judged comparable to the conventionally water blanched one for color and sensory attributes. However, a slightly higher perceivable sweetness of the RF blanched sample was found, probably due to the fact that the RF treatment allowed any contact with water to be avoided. (C) 2008 published by Elsevier Ltd.