Deciphering the Metabolic Pathways of Pitaya Peel after Postharvest Red Light Irradiation
Center of Economic Botany, Core Botanical Gardens, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China
Institute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences, Guangzhou 510600, China
College of Food Science and Technology, Hainan University, Haikou 570228, China
Author to whom correspondence should be addressed.
Metabolites 2020, 10(3), 108; https://doi.org/10.3390/metabo10030108
Received: 17 January 2020 / Revised: 20 February 2020 / Accepted: 2 March 2020 / Published: 14 March 2020
(This article belongs to the Special Issue Volatile Metabolites’ New Frontier for Metabolomics)
Red light irradiation can effectively prolong the shelf-life of many fruit. However, little is known about red light-induced metabolite and enzyme activities. In this study, pitaya fruit was treated with 100 Lux red light for 24 h. Red light irradiation significantly attenuated the variation trend of senescence traits, such as the decrease of total soluble solid (TSS) and TSS/acidity (titratable acidity, TA) ratio, the increase of TA, and respiratory rate. In addition, the reactive oxygen species (ROS) related characters, primary metabolites profiling, and volatile compounds profiling were determined. A total of 71 primary metabolites and 67 volatile compounds were detected and successfully identified by using gas chromatography mass spectrometry (GC-MS). Red light irradiation enhanced glycolysis, tricarboxylic acid (TCA) cycle, aldehydes metabolism, and antioxidant enzymes activities at early stage of postharvest storage, leading to the reduction of H2O2, soluble sugars, organic acids, and C-6 and C-7 aldehydes. At a later stage of postharvest storage, a larger number of resistance-related metabolites and enzyme activities were induced in red light-treated pitaya peel, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical-scavenging, reducing power, fatty acids, and volatile aroma.