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 NH4H2PO4. The pHs of wine samples were adjusted to various values within the range 2.5 to 4.0, or SO2 was added prior to yeast addition to give concentrations ranging from 0 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 SO2. 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 SO2 concentrations. Wine color and anthocyanin color were more stable in wines stored at lower pHs or at lower concentrations of SO2, 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 SO2/l was added. Sensory analysis indicated that the addition of SO2 at 100 mg/l when bottling imparted the best overall quality to the roselle wines stored under the various conditions tested.