Changes in Apple Polyphenoloxidase and Polyphenol Concentrations in Relation to Degree of Browning

ABSTRACT Polyphenoloxidase (PPO) activity and polyphenol concentrations decreased during maturation and remained relatively constant during cold storage. However, there was no set pattern of changes in degree of browning during maturation and cold storage. Not all cultivars showed the same relationship between degree of browning and enzyme activity. In some cultivars ( Classic Delicious, RI Greening, McIntosh and Cortland ), PPO activity was directly related to degree of browning while in others ( Empire, Rome and Golden Delicious ), degree of browning was related more to phenolic concentration. High performance liquid chromatography analysis of the phenolics in apples showed that the types of phenolic compounds in all cultivars were similar and that no one particular compound could account for the differences observed in browning.