Role of different factors affecting the formation of 5-hydroxymethyl-2-furancarboxaldehyde in heated grape must

The influence of concentration and water activity (aw) on the formation of 5-hydroxymethyl-2-furancarboxaldehyde (HMF) in thermally treated grape must was evaluated. Must was cryoconcentrated and then heated to study the pure effect of sugar concentration. Moreover, NaCl was added to the must to lower aw, maintaining the same sugar concentration, with the purpose of evaluating the pure effect of aw. Finally, the influence of minimal pH changes on the formation of HMF was evaluated by means of a model solution. The results showed that aw and sugar concentration are both determinant in the formation of HMF in grape must. Sugar concentration influences the reaction by supplying substrates; low aw enhances the formation of HMF by changing the equilibrium in the dehydration step of the reaction.