Shelf life studies on apple juice pasteurised by ultrahigh hydrostatic pressure

- Apple juice was successfully preserved by an HPP treatment.
- By using surface response methodology, optimum operating variables were determined.
- Enzymes (PPO and PME) activity was controlled by the HPP process.
- A shelf life study for 34 days was carried out on the HPP-treated juice.
- The main sensory and nutritive properties of the HPP-treated juice were preserved.

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 °C) and in refrigeration (4 °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.