Effects of fruit bagging on the physiochemical changes of grapefruit (Citrus paradisi)

Abstract

Fruit bagging is a commonly used cultivation measure to protect citrus fruit from insects and adverse environments. Present study aimed to comprehensively investigate the effects of bagging on physiochemical characteristics of grapefruit. The grape fruit were bagged at about 110-120 days after anthesis with one-layer kraft paper bag with black coating inside (SL), double-layer kraft paper bag with one black paper as inner layer (DL), and three-layer kraft paper bag with two black papers as inner layers (TL) respectively. UPLC-HRMS technique was used to identify a total of 19 flavonoids, 2 phenylpropanoids, 9 coumarins, and 5 limonoids. By using HPLC method, 50 carotenoids were identified. GCMS method was used to identify 3 soluble sugars, 3 organic acids, and 11 amino acids. In the quantitated components in the peel (albedo and flavedo), the chlorophylls and the carotenoids components (such as luteoxanthin, violaxanthin, 9-cis-violaxanthin, xanthophyll, zeaxanthin and β-carotene) were significantly down-regulated by bagging, causing the surface color of bagged fruit turn yellow earlier but paler than unbagged control, particularly in the three-layer kraft bag treatment. Unlike the peel, the color and the carotenoids contents of the juice sacs were less affected. The physiochemical compounds other than pigments, including soluble sugars, organic acids, amino acids, flavonoids, coumarins, and limonoids were minimally affected by bagging treatments. Our results indicated that bagging at about 110-120 days after anthesis exerted influence mainly on peel color, while less on sugars, acids, amino acids, flavonoids, limonoids and coumarins of grapefruit.