Changes in Color Parameters during Fermentation and Storage of Red Wine Using Thai Roselle under Different pHs and SO2 Concentrations.

Abstract

A red wine was made from must consisting of dried roselle calyces, water, yeast extract, sugar, and NH4H2P04. The pHS of wine samples were adjusted to various values within the range 2.5 to 4.0, or S02 Was added prior to yeast addition to give concentrations ranging from O to 250 mg/ l, and the wines were stored at 25'C. After storage for 35 months, the pH of each wine was regularized, and the wines were then analyzed to determine their general composition and various red color parameters. There was little difference in general composition among the wines stored under different pHS and containing various concentrations of S02' There were, however, appreciable differences in color density, color hue, and polymeric pigment color, but little difference in the wine color measured at wine pH and at pH 0.25, among the wines stored under different pHs. On the other hand, there were noticeable differences in all the above color parameters, except for color hue, among the wines stored under various S02 concentrations. Wine color and anthocyanin color were more stable in wines stored at lower pHS or at lower concentrations of S02, whereas the degree of contribution of polymeric pigment to wine color (at pH<0.5) increased with increasing storage pH and was lowest in the wines to which 100 or 150 mg S02/1 was added. Sensory analysis indicated that the addition of S02 at 100 mg/ I when bottling imparted the best overall quality to the roselle wines stored under the various conditions tested.