Investigations on the formation of α-dicarbonyl compounds and 5-hydroxymethylfurfural in fruit products during storage: New insights into the role of Maillard reaction

The formation of α-dicarbonyl compounds and 5-hydroxymethylfurfural was investigated under different conditions and the amino acid adducts of them were confirmed using high-resolution mass spectrometry in fruit products during storage. Changes in the concentrations of sugars, amino acids, α-dicarbonyl compounds, and 5-hydroxymethylfurfural in fruit juice concentrates and dried fruits were monitored. Among the dicarbonyls, glucosone was the dominant one in 30 °Bx of fruit juice concentrates, whereas 3-deoxyglucosone was the major in 50 and 70 °Bx of those and in all dried fruits during storage. The highest level of 3-deoxyglucosone was found as 7251 ± 896.6 mg/kg in dried date at the end of the storage. During storage, the loss of free amino acids significantly increased (p < 0.05) in the higher initial reactant concentrations in fruit juice concentrates. The confirmation of amino acid adducts of dicarbonyls and 5-hydroxymethylfurfural generally with high mass accuracy proved the contribution of Maillard reaction to non-enzymatic reactions in fruit products.