Biochemical Analysis of Browning Activities in Apples

Abstract

This study investigates the differential browning mechanisms among various cultivars of apples. The biochemical mechanism responsible for browning activities in apples involves a group of enzymes known as polyphenol oxidases (PPO). These enzymes facilitate the reaction between polyphenolic substrates (PPS) and oxygen in the production of benzoquinones, a compound that auto-polymerizes to form melanin, the primary browning agent in apples. In this study, both the PPO and PPS were extracted from five distinct apple cultivars, namely Fuji, Red Delicious, Gold Rush, Ruby Frost, and Mutsu. To identify the types of PPO in each subspecies, the reactivity of the extracted enzyme from each cultivar was quantified in the presence of three known substrates, catechol, catechin, and chlorogenic acid using UV-vis absorption spectrophotometry. The reactivity of the PPO extract with each substrate was compared across the five apple cultivars to identify the specificity of PPO to type(s) of PPS present and to quantify the concentration of PPO present in each species. Browning activity directly affects the longevity of fruits and vegetables, which is a consistent problem in the agricultural industry. If the biochemical mechanism of browning activity is better understood, it could lead to improvements in future food production, storage, and transportation methods.