Postharvest light-emitting diode irradiation of sweet cherries (Prunus avium L.) promotes accumulation of anthocyanins

Light influences postharvest formation of bioactive compounds in fruit and vegetables. The objectives of this study were to determine the physicochemical changes and phenylalanine ammonia lyase and flavonoid 3'-hydroxylase activities in sweet cherries (Prunus avium L.) irradiated with light-emitting diodes. Cherries were stored under light-emitting diodes for 10 days, exposed to UV-B and blue light, and to the combination of white, blue and green light. Irradiation with blue light significantly increased the anthocyanin content (cyanidin 3-O-glucoside, cyanidin 3-O-rutinoside) and significantly influenced the CIE color parameters hue, C* and Delta E. Combined white-blue-green light provoked similar but less pronounced effects, while UV-B light was similar to control (in the dark). Blue and white-blue-green light increased phenylalanine ammonia lyase activity. Light irradiation had no significant effects on ascorbic acid and the phenolic profile. Highly significant correlations were found between anthocyanins and phenylalanine ammonia lyase on the one side, and the color parameters hue, C* and Delta E on the other.