Metabolomic profiling of matured coconut water during post-harvest storage revealed discrimination and distinct changes in metabolites

Abstract

The metabolites of coconut water stored at room temperature were analyzed using UPLC-MS/MS and multivariate statistical analysis to identify the differential biomarkers and metabolic pathways during post-harvest storage. Principal component analysis (PCA), partial least squares-discriminate analysis (PLS-DA), and orthogonal projections to latent structures discriminant analysis (OPLS-DA) were employed to analyze the UPLC-MS/MS data set of 34 matured coconut water samples collected after 0, 1, 2, 3, 4, and 5 months of storage (MOS); moreover, the p-value and fold change were chosen to identify the differential biomarkers; furthermore, a KEGG pathway was applied to analyze the metabolic pathways. All samples were discriminated well in the OPLS-DA model and were divided into two clusters: groups A (0 MOS, and so on), B, C, and D were in one cluster, and groups E and F were in another. A total of 18 biomarkers were identified among all groups and 12 biomarkers between groups A and E, from which we concluded that the post-harvest storage life of matured coconut water shall not exceed 3 months and the pathways of the TCA cycle, protein hydrolysis from coconut meat, and interconversion among amino acids were mainly enriched during the post-harvest storage.

Fig. 1. Appearance changes of coconut water during storage. ^a MOS: months of storage.

Fig. 2. Changes in conductivity, °Brix, pH and sugar/acid ratio of matured coconut water during storage.

Fig. 3. Upregulated and downregulated DE metabolites, PCA score plots, PLS-DA score plots, and OPLS-DA score plots based on NT-pos ((a)–(d)) and NT-neg ((e)–(h)).

Fig. 4. (a) Heatmap for the differential biomarkers combined with hierarchical cluster analysis, (b) correlation matrices of biomarkers, and (c) pathway analysis based on biomarkers of matured coconut water during storage.

Fig. 5. (a) Ranking the 12 biomarkers according to their importance; (b) correlation matrices of biomarkers, and (c) pathway analysis based on biomarkers of matured coconut water between group A and E.