Shelf life studies on apple juice pasteurised by ultrahigh hydrostatic pressure

Shelf life of Golden Delicious apple juice treated by ultrahigh hydrostatic pressure (HPP) was evaluated in terms of colour, total polyphenol content, antioxidant capacity, ascorbic acid content, pH, titratable acidity, total soluble solids, polyphenol oxidase (PPO) activity, pectin methylesterase (PME) activity and sensory testing. Using response surface methodology it was determined to process the apple juice in a HPP unit at 430 MPa for 7 min, and stored at room temperature (20 degrees C) and in refrigeration (4 degrees C) for 34 days. No significant changes (p < 0.05) in physicochemical properties, nutritive value or sensory attributes were detected in the treated apple juice, but the PPO started recovering its activity during the storage without causing significant difference (p < 0.05) in its colour. PME was completely inactivated in the HPP treatment, while indigenous micro-biota of the raw juice was also eliminated. The applied processing conditions preserved the physicochemical and sensory quality of apple juice, and kept polyphenols content and antioxidant capacity unaltered. (C) 2014 Elsevier Ltd. All rights reserved.