Effects of negative air ion treatment on postharvest storage quality and anthocyanin metabolism of grape

Grapes are rich in anthocyanin but are prone to postharvest quality deterioration. Many studies proved that negative air ion (NAI) preserved horticultural products. We hypothesized that NAI kept postharvest quality and repressed anthocyanin degradation of grape. In this study, NAI delayed grape firmness loss, mitigated rot and shattering gloss. It also preserved quality attributes like total soluble solids, acidity, vitamin C (Vc), phenols, and anthocyanins. Among treatments, NAI3 (treat with NAI every 3 days for 1 h) was most effective. Ultra-high performance liquid chromatography analysis showed NAI3 increased delphinidin, malvidin, paeonidin, petunidin, and pelargonidin levels while reducing cyanidin. NAI3 maintained activities of anthocyanin synthesisrelated enzymes and inhibited degradation-related ones. Gene expression analysis showed NAI3 induced synthesis-related genes and inhibited degradation-related genes. Thus, NAI maintained anthocyanin content and composition by regulating activities and gene expressions of enzymes involved in anthocyanin metabolism, playing a crucial role in grape storage.