Application of induced voltage in cloudy apple juice: enzymatic browning and bioactive and flavouring compounds

Controlling enzymatic browning and decreasing the loss of phenolic and flavour compounds by emerging technologies have drawn interest. In this study, magneto-induced voltages (900-1800 V, 20-45 kHz) with mild temperature (20-50 degrees C) were applied to inactivate polyphenol oxidase (PPO) and peroxidase (POD) in cloudy apple juice. Results suggested that PPO and POD activities could be reduced by 98.5% and 99.4%, respectively, following the condition: induced voltage 1800 V; frequency 45 kHz; temperature 50 degrees C and duration 3 min. And, phenolic compounds included gallic acid, catechin, chlorogenic acid, p-hydroxybenzoic acid, caffeic acid, rutin and p-coumaric acid, as well as major aroma compounds consisted of 22 volatile constituents which classified into three categories: esters, alcohols and aldehydes were also investigated. It suggested the phenolic compounds and major aroma compounds remained unchanged after the electrical treatment. This study suggests that the induced voltage produced by electromagnetic induction is an alternative to conventional heating methods.