Comparative analysis of carotenoids and metabolite characteristics in discolored red pepper and normal red pepper based on non-targeted metabolomics

Discoloration of red peppers, such as fading and color desaturation, can occur during harvesting, drying and storage. In this study, liquid chromatography-mass spectrometry (LC-MS) was used to identify and quantify carotenoids. Metabolomics analysis based on ultra-high performance liquid chromatography coupled with a quadrupole extractive orbitrap mass spectrometery (UHPLC-QE Orbitrap/MS) was performed to determine the metabolites present in discolored red peppers and normal red peppers. This approach showed that the carotenoid composition of discolored red peppers was similar to that of normal red pepper, but that the carotenoid content was reduced overall, damaging the structural stability of cell tissues and resulting in the discoloration phenomenon. Additionally, metabolomics analysis showed that, 408 differentially accumulated metabolites, especially the lipids and their derivatives and flavonoids exhibited significant differences between the discolored and normal red pepper. In addition, the distinguishing metabolites of discolored and normal red pepper indicated that the discoloration is closely related to the plant response to biotic and abiotic stress. These results suggested that lipid and flavonoid syntheses are significantly correlated with discoloration formation, and provide valuable information for future studies examining the functions of major metabolites in preventing discoloration.