• grapes;
  • nonenzymatic browning;
  • acidity;
  • reducing sugars;
  • storage


The effect of storage on juice concentrate from 2 red grape (Merlot and Criolla) and 1 white grape (Yellow Muscat) varieties on color and chemical composition, at temperatures ranging from 10 to 30 °C, was investigated. Color deterioration as A420 occurred at a faster rate in juice made with Merlot variety. The same was true when the pigment destruction as A520/420 was studied. Total reducing sugar, fructose-to-glucose ratio, and proline (the only significant amino acid present in grape juice) remained practically constant during storage. The hydroxymethyl-furfural (HMF) buildup reaction proceeded faster in Criolla grape juice. Independent of variety, a detectable amount of HMF was produced only after 12 wk of storage at any temperature.