Metabolic variations in the pulp of four litchi cultivars during pulp breakdown.

Fruit of four litchi cultivars were stored at 25 ± 1 °C. The shelf life changed from long to short respectively was "Feizixiao (FXZ), "Jingganghongnuo (JGHN)", "Huaizhi (HZ)" and "Nuomici (NMC)". During pulp breakdown, marketable fruit and total soluble solids (TSS) decreased significantly, while respiratory rate increased significantly. After metabolomics analysis, a total of 179 metabolites were detected in litchi pulp, including 56 primary metabolites, 79 volatile compounds, 28 free amino acids and 16 hydrolyzed amino acids. Compared with other litchi cultivars, FZX pulp was rich in volatile alcohols and amino acids, NMC pulp was rich in soluble sugars and sesquiterpenes, and JGHN and HZ pulp were rich in sesquiterpenes. During the postharvest storage, most of volatiles and amino acids were induced in NMC pulp, while most of volatiles were reduced in JGHN and HZ pulp. The specific metabolites accumulated in a litchi pulp might be related to its shelf life and fruit quality. The increased metabolites during pulp breakdown might be also related to the resistance of litchi pulp.