Metabolic response of organic strawberries and kiwifruit subjected to PEF assisted-osmotic dehydration

This research aims to evaluate the effect of pulsed electric field (PEF) pre-treatment for osmotic dehydration (OD) on physiological changes in organic strawberries and kiwifruits, in terms of metabolic heat production, measured by isothermal calorimeter, and of tissue damage, evaluated by fluorescence microscopy, texture analysis, and electrolytes leakage. Fruits were pre-treated at two electric field strengths (100 and 200 V/cm) using 100 near-rectangular shaped pulses (pulse width: 10 μs, repetition time: 10 ms) and then subjected to OD in hypertonic solutions (40% w/w) of sucrose or trehalose, both added with calcium lactate 1%. Results showed that OD alone allowed to retain the functionality of the membranes causing only a decrease in the endogenous heat production. The application of low electric field strength (100 V/cm) generally preserved the cell viability, which was drastically reduced after OD treatment. On the contrary, the application of 200 V/cm caused tissue damage and loss of cell vitality, probably due to irreversible electroporation. Industrial application: PEF could be an interesting pre-treatment for reducing the intensity of osmotic dehydration of fruits. However, it is important to understand the implication of the treatment on the tissue metabolism and structure to control the effect on the quality of the final product. This study provides some useful information that could be exploited for the industrial production of intermediate moisture fruit products.