Heat-induced chemical modification of grape must as related to its concentration during the production of traditional balsamic vinegar: a preliminary approach

Occurrence and concentration of some furanic compounds during grape must concentration were studied by high-performance liquid chromatography with diode array detection. A progressive decrease of the glucose/fructose ratio was observed, along with a progressive increase of cyclic oxygenated compounds, which followed sugar concentration. Furoic acid, furfural, and 5-hydroxymethylfurfural were detected and quantified, with the latter found to be the main substance in this group. One other unknown substance with a furan-like UV spectrum was detected. Its accumulation profile was irregular, apparently scarcely influenced by sugar concentration. Two parameters that describe colour (optical absorbance at 280 and 420 nm), pH and reducing sugar content are studied.