Effect of temperature and insoluble solids added to clarified musts on fermentation rate and wine quality

Abstract

The effect of suspended solids added to clarified musts on fermentation rates and qualities of wines from grape cultivars Thompson Seedless and Arka Kanchan was studies with two fermentation temperature (13 and 18 ºC) and compared with cold settled and centrifuged juice. The suspended solids such as grape solids and bentonite were added at 15 and 2% and 400 mg and 800 mg/1, respectively. In case of Thompson Seedless musts fermented at 13 ºC both the maximum and overall fermentation rates were high when either grape solids or bentonite was added. When fermented at 18 ºC, only bentonite addition increased the fermentation rates. However, the cold settled juice fermented faster than the juice with suspended solids at 18 ºC. in case of Arka Kanchan fermented at 13 ºC the maximum fermentation rates increased with higher solids contents, but overall fermentation rates didn’t show much difference. At 18 ºC both maximum and overall fermentation rates were higher in all the treatments except in juice with 1% solids. Varietal comparison showed that the musts of Thompson Seedless fermented faster at 13 ºC while Arka Kanchan at 18 ºC. The alcohol content, total acidity, pH and tannin were not affected by addition of suspended solids. Volatile acidity was in all the treatments and was within the range. Residual sugar was low in all the treatments indicating that the fermentation was complete in all the samples. Sensory evaluation of wines indicated that in case of Thompson Seedless must the quality of wine was better when fermented at low temperature with bentonite. However, at high temperature, wine from centrifuged must was better. Better quality wine obtained from Arka Kanchan, when centrifuged juice was fermented at both the temperatures. 19