COMPARISON OF ENZYMES AND FLAVONOIDS RELATED TO POSTHARVEST BROWNING IN THREE LITCHI (LITCHI CHINENSIS SONN.) CULTIVARS

ABSTRACT The experiments were performed to compare differences of enzymes and flavonoids related to postharvest browning in three litchi cultivars cv. “Nuomici,”“Heli” and “Feizixiao.” By high-performance liquid chromatograph analysis, the major flavonoids from pericarp tissues were identified as (−)–epicatechin (EC), (−)–epigallocatechin (EGC) and proanthocyanidin A2 (PA2). These flavonoids were ortho dihydric or triatomic phenols serving as potential substrates for enzymatic browning reaction. It was further observed that the similar flavonoid components existed in three cultivars. In addition, comparing three litchi cultivars, cv. “Nuomici” exhibited higher activities of polyphenoloxidase (PPO) and peroxidase (POD) as well as higher contents of potential substrates EC, EGC and PA2, indicating that this cultivar had the stronger capability of enzymatic browning reaction. After the ripe fruits were harvested, cv. “Nuomici” would brown quickly. However, cv. “Heli” possessed the highest EC, EGC and PA2 contents but the lowest PPO and POD activities, and contrarily cv. “Feizixiao” had higher PPO and POD activities but the lowest EC, EGC and PA2 contents, suggesting that both cultivars browned more slowly than cv. “Nuomici” after harvest. PRACTICAL APPLICATIONS Enzymatic browning of pericarp tissues seriously influences the quality of harvested litchi fruit. The browning level of various litchi cultivars is closely correlated with the differences of enzyme activities and flavonoid contents. The aim of the present study was to compare differences of enzymes and flavonoids related to postharvest browning in three common litchi cultivars. This study helped in comprehending the postharvest storage characteristics of different litchi fruits and provided a practical reference for selection and breeding of litchi cultivars with good shelf life.