Comparison of biochemical properties and thermal inactivation of membrane‐bound polyphenol oxidase from three apple cultivars ( Malus domestica Borkh)

Summary A comparative study of the properties of membrane‐bound polyphenol oxidase ( mPPO ) from three apple cultivars, namely Red Fuji ( FJ ), Granny Smith ( GS ) and Golden Delicious ( GD ), was carried out for the first time. Data indicate that mPPO s from three cultivars exhibit significantly different properties. GS mPPO had the strongest affinity to catechol, but FJ mPPO had the highest maximum velocity. Red Fuji ( FJ ) mPPO had the significantly higher activity than those of GD and GS mPPO s. Red Fuji ( FJ ) mPPO had the highest activity at pH 8.00, while GD and GS mPPO s at 4.50 and 7.50–8.00, respectively. Red Fuji ( FJ ) mPPO was more stable than GD and GS mPPO s over the pH range of 5.0–8.5. The optimal temperature for GS mPPO was within 70–75 °C, which is higher than those for mPPO s from FJ and GD . Thermal inactivation of the three mPPO s followed a first‐order kinetic model with different inactivation kinetic parameters.