Assessment of taste profile dynamics during crabapple (Malus prunifolia (Willd.) Borkh.) ripening by metabolomics and electronic tongue analysis

Crabapple (Malus prunifolia (Willd.) Borkh) is valued for its ornamental appearance, effectiveness as a rootstock, and rich nutritional profile. However, the flavor profile and metabolite composition are poorly characterized, which hinders a comprehensive assessment of its overall value. This study combined broad-spectrum untargeted metabolomics with electronic tongue analysis to systematically characterize the flavor and metabolite profiles of M. prunifolia across four distinct ripening stages, thereby clarifying the relationship between flavor and metabolites and uncovering the metabolic basis of flavor formation. The results indicated that the fundamental flavor characteristics remained relatively stable throughout ripening, with an overall trend toward increased sweetness and reduced sourness, bitterness, and astringency. Among these attributes, sweetness and sourness were the primary indicators of ripeness. The increase in sweetness was associated with changes in fructose, glucose, sucrose, D-mannitol, and D-sorbitol, and the reduction in sourness was associated with changes in ketoglutaric acid, aconitate, as well as significant enrichment of glyoxylate and dicarboxylate metabolism. Diverse flavonoids (including quercitrin, astragalin, rutin, mangiferin, neohesperidin, catechin, and (−)-epicatechin), triterpenoids (including maslinic acid, corosolic acid, and alphitolic acid), and phenolic acids (including cryptochlorogenic acid) were identified. While these metabolites contribute to bitterness and astringency, and also impart substantial functional properties. The results provide a reference for assessing the nutritional value of M. prunifolia, facilitating resource utilization and targeted extraction of bioactive compounds.