Effect of a combination of electrodialysis with bipolar membranes and mild heat treatment on the browning and opalescence stability of cloudy apple juice

The purpose of this work was to develop a process enabling the quick inactivation of the polyphenol oxidase and pectin methylesterase enzymes, which are present in cloudy or unclarified apple juice; These enzymes are respectively responsible for enzymatic browning and opalescence instability. In order to fulfill this objective, acidification of the apple juice to pH 2.0 was conducted by electrodialysis (bipolar–anionic membranes) followed by mild heat treatment at temperature of 40, 45 and 50 °C for a duration of 0–60 min. Then, juice pH was readjusted to its initial value by electrodialysis with bipolar–anionic membranes. It was shown that a mild heat treatment at 45 °C for 5 min performed on the acidified juice represents an appropriate condition to quickly inactivate the enzymes. Furthermore, the organoleptic properties of the juice after treatment were found to be preserved and the adjusted juice (pH readjusted to its initial value) shows a better color than an untreated apple juice. Opalescence of the adjusted juice was also more stable than for an untreated cloudy apple juice, when stored at 4 °C for 3 months.