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Abstract
This study explored the metabolic mechanisms of key pecan flavor compound formation using pathways-based metabolomics, and statistical correlation analysis. Key pecan flavor compounds were identified, and metabolites (precursors and intermediates) that lead to the formation of those flavor products were investigated. Pathways elucidated include 2,3-butanedione and 3-penten-2-one biosynthesis, phenylalanine biosynthesis and metabolism, terpenoid backbone biosynthesis, lipoxygenase pathways, and vanillin biosynthesis, flavonoid, benzoic acid biosynthesis and sucrose metabolism. Other important primary and secondary metabolites were also analyzed. Three cultivars of raw pecans (“Avalon”, “Desirable” and “Sumner”) were collected and evaluated. A total of 93 distinguished metabolites were identified which include 57 non-volatiles (organic acids, carbohydrates, amino acids, phenylpropanoids), 17 fatty acid methyl esters (FAMEs), and 19 volatiles compounds. Based on the results, possible metabolic mechanisms for the formation and regulation of key flavors in pecans were identified and discussed. The pathways-based metabolomics reveal that flavor precursors and intermediates are consistent with the final flavor products. Statistical correlation analysis confirmed a strong positive relationship between precursors (glucose, pyruvate, cis-aconitate, isocitrate) and products (2,3-butanedione, ethanol, and 3-penten-2-one). This supports that the biosynthesis of 3-penten-2-one, 2,3-butanedione, and ethanol are major metabolic pathways contributing to the buttery, sweet and fruity flavor in pecans. With these novel strategies, the regulated metabolic flux through the pathways was elucidated for the first time, revealing potential mechanisms for the formation and regulation of key flavors in pecans. Thus, this finding will serve as preliminary data for future research and breeding programs aimed at improving or maintaining flavor quality of pecans.