Ohmic heating/vacuum treatments and cooled storage effect on polyphenols retentions of osmodehydrated apples

Abstract

Polyphenols are important bioactive compounds of apples and they contribute positively to human health. Consumer demand has increased the application of mínimal processing techniques to preserve organoleptic and nutritional properties of raw fruits for longer. The aim of this study was to analyze the combined effect of ohmic heating (OH), pulsed vacuum (PV), osmotic dehydration (OD) and refrigerated storage on polyphenol compounds and physical properties of apples cubes. Treatments were performed using a 65 °Brix sucrose solution at 30°C, 40 "C or 50°C for 120 min, and then samples were stored for 28 days at 5 °C. OH provides an electric field of 13 V/cm and pulsed vacuum was applied for 5 min at the beginning of the process. Results indicated that lower process temperatures retain more polyphenol compounds after treatment, but during refrigerated storage at higher process temperature, the retention of these compounds was better, due to the polyphenoloxidase inactivation. Considering the greater mas s transfer, lower color difference and better retention of polyphenols, PVOD/OH treatment at 50°C was the best process to obtain a partially dehydrated apple.