Spatial and Temporal Distribution of Four Organic Acids during Post-Ripening of ‘Fenjiao’ Bananas Observed by Mass Spectrometry Imaging

Abstract

Organic acids are among the primary substances affecting the flavor of ‘Fenjiao’ bananas. Several previous studies have characterized organic acids and their corresponding biosynthetic pathways in ‘Fenjiao’ bananas; however, chemical information about the spatial and temporal distributions of the organic acids in the bananas is absent. In this study, air flow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI) for analyzing organic acids in ‘Fenjiao’ bananas was developed. The organic acids in the peel and pulp of ‘Fenjiao’ bananas were detected and imaged in situ, and the spatial distribution of organic acids in banana fruit tissue slices were visualized. The results were validated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that the MSI method can provide more accurate spatial and chemical localizations of the four primary organic acids (i.e., citric, malic, fumaric, and quinic acids) in the same tissues of ‘Fenjiao’ bananas. However, the quantification of the concentrations in different tissues is adversely affected by inaccuracy due to matrix effects. The in situ determination of the organic acids in ‘Fenjiao’ bananas can assist to understand the spatial and temporal distribution of organic acids in bananas, which provides a new method and idea to explore the biosynthesis and accumulation pattern of metabolites.