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

Fruit bagging is a commonly used cultivation measure to protect citrus fruit from insects and adverse environments.The present study aimed to comprehensively investigate the effects of bagging on the physiochemical characteristics of grapefruit.The grapefruit were bagged at approximately 110–120 d after anthesis with a one-layer kraft paper bag with black coating inside(SL),a double-layer kraft paper bag with one black paper as the inner layer(DL),and a three-layer kraft paper bag with two black papers as inner layers(TL),respectively.Ultra performance liquid chromatography-high resolution mass spectrometry(UPLC-HRMS)technique was used to identify a total of 19 flavonoids,2 phenylpropanoids,9 coumarins,and 5 limonoids.By using UPLC,50 carotenoids were identified.Gas chromatography–mass spectrometry 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 andβ-carotene)were significantly downregulated by bagging,causing the surface color of bagged fruit to turn yellow earlier but paler than that of the unbagged control,particularly in the three-layer kraft bag treatment.Unlike the peel,the color and the carotenoid content of the juice sacs were less affected.The physiochem-ical 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 approximately 110–120 d after anthesis exerted influence mainly on peel color,but less on sugars,acids,amino acids,flavonoids,limonoids and coumarins of grapefruit.