Biochemical characterization of enzymatic browning in selected apple genotypes

Abstract

Enzymatic browning in apples (Malus × domestica Borkh.) caused by polyphenol oxidases (PPO) is the major factor responsible for the deterioration of quality in processed apple products such as juice, fresh-cut slices, and chips. Selected apple genotypes with a range of low post-cut enzymatic browning were investigated to understand the biochemical mechanisms leading to enzymatic browning. Post-cut enzymatic browning, polyphenolic profiles using LC-MS/MS, PPO activity, vitamin C, total antioxidant capacity using the Ferric Reducing Antioxidant Power (FRAP) and the Oxygen Radical Absorbance Capacity (ORAC), and elemental composition were determined in two recently released cultivars [Eden™(also known as SJCA38R6A74) and SuperMac], and one new advanced line (SJCA16) and compared with two commercial cultivars (Empire and Cortland). Eden™ exhibited the least post-cut enzymatic browning as estimated by Whiteness Index. SJCA16 possessed a characteristic yellowish flesh color. Whiteness Index (WI) values were inversely related to chlorogenic acid, catechin and epicatechin contents present in apple slices. Vitamin C content showed a strong positive correlation with WI. Among the mineral elements, the content of copper had a strong positive correlation with PPO activity. Key words: Apple genotypes, enzymatic browning, polyphenoloxidase, polyphenolics, Whiteness Index, total antioxidant capacity