Osmodehydration assisted by ohmic heating/pulse vacuum in apples (cv. Fuji): retention of polyphenols during refrigerated storage

Apples are a widely consumed fruit and have a high polyphenol content. The aim of this study was to analyse the combined effects of osmotic dehydration (OD) and ohmic heating (OH) with a pulsed vacuum (PV) on polyphenol retention during the stored refrigeration of apple cubes. Treatments were performed using a 65 degrees Brix sucrose solution at 30, 40 or 50 degrees C for 120 min, and then, samples were stored for 28 days at 5 degrees C. OH provides an electric field of 13 V cm(-1), and a pulsed vacuum was applied for 5 min at the beginning of the process. The results indicated that a lower temperature process (30-40 degrees C) resulted in the retention of more polyphenol compounds after treatment than a higher temperature process (50 degrees C). Nevertheless, during refrigerated storage, we observed that 50 degrees C preserved these compounds better due to polyphenol oxidase inactivation. PVOD/OH treatment at 50 degrees C was determined to be the best retention of polyphenols from the fresh apple for dehydrating apples.