Analysis on quality differences associated with metabolomics of rambutan during different temperature storage

This study aimed to understand how temperatures differentially impact the crucial quality indices and metabolites in rambutan during storage. Rambutan browned quickly at room temperature from 0 d (control). After ten days at 5 ℃, browning index and lightness were 4.2% and 147.5%, compared with rambutan stored at 1 ℃, which was the best quality achieved. An UPLC-MS/MS was performed to uncover the metabolism underlying those quality differences, followed by the analysis of KEGG pathways. Results showed that 276 differentially expressed metabolites (DEMs) screened were enriched in 18 KEGG pathways. The pathways related to carbohydrates, aliphatic metabolites, and organic acids were highly active in rambutan stored at room temperature, whereas the pathways related to amino acids biosynthesis and nucleotides were highly active in rambutan stored at 1 ℃, 5 ℃. These findings indicated that increased scopoline was associated with serious browning at room temperature. L-leucine and L-isoleucine both increased in response to low temperature and reduced browning. Glutathione and ascorbate decreased to 4.89% and 4.36%, compared with 0 d (CK) in rambutan with severe browning stored at 1 ℃ for ten days. However, no significant changes in those two metabolites were observed in rambutan stored at optimal 5 °C for ten days. Thus glutathione and ascorbate could be used as potential indicators of browning degree. Our study provided a metabolic insight into the role of temperature on rambutan quality and browning.