Comparative Analysis of the Effect of Pre-Harvest Bagging and Non-Bagging Treatment on Fruit Quality of ‘Younai’ Plum by UPLC-MS/MS and GC-IMS

In this study, ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and gas chromatography-ion mobility spectrometry (GC-IMS) combined with multivariate statistical analysis were used to analyze the effect of pre-harvest bagging on metabolites, metabolic pathways and volatile composition in ‘Younai’ plum fruit. The results showed that the peel and pulp of ‘Younai’ plum subjected to pre-harvest bagging treatment were yellow. By UPLC-MS/MS, 604 metabolites were identified, pre-harvest bagging changed the metabolic characteristics and pathways, and 58 significantly differential metabolites were selected, 22 and 36 of which were up-regulated and down-regulated, respectively. Among them, the contents of taste-related substances such as sugars and organic acids were not significantly different, and the contents of taste-active amino acids taste were significantly different between the bagging and non-bagging groups. By GC-IMS, 27 volatile substances were identified, including 14 aldehydes, 5 esters, 4 alcohols, 3 ketones and 1 other compounds. Most esters were more abundant in non-bagged fruits, while most alcohols were more abundant in bagged fruits. The fingerprints of volatile components in ‘Younai’ plum with pre-harvest bagging and non-bagging treatment were different. By searching against the Traditional Chinese Medicine System Pharmacology Database and comparing them with identified metabolites, 199 active ingredients were identified, and 37 key active ingredients were obtained according to the screening criteria. Among them, only quercetin was down-regulated in ‘Younai’ plum after pre-harvest bagging treatment. In conclusion, pre-harvest bagging can improve the appearance quality, but it may also have an effect on the taste-active, aroma-active and functional components of ‘Younai’ plum.