Maillard reaction and caramelization during hazelnut roasting: A multiresponse kinetic study

•1,2-Enolization is important in the interconversion of glucose and fructose.•5-Hydroxymethylfurfural formation proceeds via fructofuranosyl cation dehydration.•Methylglyoxal and dimethylglyoxal mainly form from 1-deoxyglucosone.•Glyoxal forms through glucose degradation during roasting in hazelnuts.•α-Dicarbonyl compounds could have a role in the formation of melanoidins. A comprehensive kinetic model indicating the elementary steps of Maillard reaction and caramelization during hazelnut roasting was proposed based on a multi-response kinetic modeling approach. Changes in the concentrations of sucrose, fructose, glucose, amino acids, 3-deoxyglucosone, 1-deoxyglucosone, 3,4-dideoxyglucosone, glyoxal, methylglyoxal, dimethylglyoxal, and 5-hydroxymethylfurfural were examined in hazelnuts during roasting at 150, 160 and 170°C for 15, 30, 60, 90, and 120min. The results suggested that 1,2-enolization was important in the interconversion of glucose and fructose, 5-hydroxymethylfurfural formation mainly proceeded via fructofuranosyl cation dehydration rather than 3-deoxglucosone, glucose contributed more than fructose and fructofuranosyl cation to the early stage of the Maillard reaction. Methylglyoxal and dimethylglyoxal were mainly formed from 1-deoxyglucosone with high reaction rate constants while glyoxal formed through glucose degradation. α-Dicarbonyl compounds could have a role in the formation of melanoidins. The temperature dependence of the reactions was complicated and could not be explained by the Arrhenius equation.