Color stability of apple derivatives by radiofrequency treatments

In the last decade the demand for high quality and stable fruit and vegetables with fresh like appearance has greatly increased. Among the fruits, apples represent one of the mostly used for both direct consumption and processing. However, one issue for apple stability is represented by enzymatic browning. Here we studied the possibility to increase color stability of apple derivatives by means of radiofrequency (RF) treatments. In particular, the effect of increasing RF electric fields on the activity of oxidative enzymes was studied in model systems and food. Firstly, the mechanisms of enzyme inactivation by RF treatments were studied on polyphenoloxidase (PPO) model systems. RF treatments efficiently inactivated the enzyme. 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.