Inactivation of apple (Malus domestica Borkh) polyphenol oxidases by radio frequency combined with pulsed electric field treatment

다국어 초록 (Multilingual Abstract)

Radio frequency (RF) preprocessing combined with pulsed electric field (PEF) processing was employed to inactivate polyphenol oxidase (PPO) in apple juice. PPO enzyme levels, loss of total phenolic content (TPC), colours and volatile components in the apple juice were subsequently determined and compared with conventional processing methods (60 °C for 10 min and 70 °C for 10 min). Results indicated that, when the apple tissue was preprocessed using RF for 10 min, the residual activity of PPO decreased to 13.57%; when the squeezed juice was processed by PEF, the residual activity decreased to about 5% at 15–35 kV cm−1 for 400 μs. RF treatment caused no significant loss in TPC. Compared with the conventionally processed samples, the apple juice that was RF‐treated for 10 min and PEF‐treated at 15 kV cm−1 for 400 μs increased its lightness and maintained its fresh‐like flavour.
Apple juice which is squeezed from apples pre‐processed by radio frequency is treated by pulsed electric field treatment to inactivate the PPO efficiently and improve the juice qualities.