Identification and verification of key taste components in wampee using widely targeted metabolomics

Abstract

Due to the lack of comprehensive evaluation of all metabolites in wampee, the metabolic reasons for taste differences are unclear. Here, two local varieties YF1 (sweet taste) and YF2 (sweet-sour taste), were selected for quality analysis, followed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) based widely targeted metabolomic analysis. YF1 and YF2 were clearly separated by principal component analysis (PCA) and cluster analysis, and 449 metabolites were different between the cultivars, including 29 carbohydrates and 29 organic acids. Among them, d-galactose, d-mannose, and d-fructose 6-phosphate contributed mainly to the sweet taste of the YF1 wampee. l-citramalic acid, 2-hydroxyglutaric acid, and 3-methylmalic acid were the dominant organic acids in YF2 wampee, and therefore, contributed primarily to the sweet-sour taste. The differential metabolites were significantly enriched in the "ascorbate and aldarate metabolism" and "C5-branched dibasic acid metabolism" pathways. Ascorbate played a crucial role in the regulation of sugars and organic acids through those pathways. In addition, high-performance liquid chromatography (HPLC) based quantitative verification exhibited the same specific cultivar variations.

Keywords: Cultivar; Metabolomics; Sweet taste; Sweet–sour taste; Wampee.

Fig. 1

Mature fruits of YF1 and YF2 wampees.

Fig. 2

Differential fruit chemotype between YF1 and YF2. (A) PCA analysis of metabolites identified from YF1, YF2 and mix sample. Equal weight of YF1 and YF2 flesh samples were mixed for use as quality control. Each group had three individual samples. For example, YF1-1, YF1-2, YF1-3 were three YF1 wampee samples. (B) Hierarchical cluster analysis of metabolites from YF1 and YF2. The color from green (low) to red (high) indicates the level of each metabolite. The Z score represents the deviation from the mean by standard deviation units.

Fig. 3

Differential metabolites between YF1 and YF2. (A)Volcano plot of the 1012 metabolites identified. (B) Pie chart of the biochemical categories of the 449 differential metabolites.

Fig. 4

Maps of KEGG pathways involved in key differential metabolites. Note: The pathway maps include “ascorbate and aldarate metabolism” and “C5-branched dibasic acid metabolism”. The colored circles in front of each metabolite indicate log₂YF2/YF1 values.

Fig. 5

Quantitative verification of key taste metabolites by HPLC. (A) Quantitative verification of carbohydrates. (B) Quantitative verification of organic acids. Note: ** on the column meant extremely significant difference between YF1 and YF2 wampees (p < 0.01).