Color of Riesling and Vidal Wines as Affected by Bentonite, Cufex°

Browning has been controlled by sulfur dioxide (SO2 ) in wine for many years, but other compounds also have the potential to reduce browning. Bentonite, Cufex and SO2 were applied to juice from Riesling grapes Vitis vinifera L. and Vidal grapes, a French-American Hybrid to compare their effects on wine browning. Seven treatments (control, 35 mg/L SO2, 70 mg/L SO2, 120 mg/L bentonite, 240 mg/L bentonite, 90 mg/L Cufex and 150 mg/L Cufex) were applied to the juice. Two levels of SO2 (0 and 20 mg/L) and two storage times (initial and 3 months at 37°C) were established on each of the seven treatments after fermentation was complete. The SO2 juice treatments resulted in the least browning (absorbance at420 nm), and bentonite and Cufex treatments were also less brown than the control. Sulfur dioxide juice treatments and SO2 at bottling increased green and reduced yellow color as was shown by lower Gardner Color Difference meter 'a' and `b' values. The addition of 20 mg/L SO2 at bottling further decreased browning but was more effective in Riesling than in Vidal wines. Three months storage at 37°C increased browning almost two-fold as compared to initial readings.