Effect of ethanol, glycerol, glucose/fructose and tartaric acid on the refractive index of model aqueous solutions and wine samples.

The refractive index is a basic optical property of materials. This study explores the effect of ethanol, glycerol, tartaric acid and glucose/fructose on the refractive index in model aqueous solutions and in dry white wines. Various model aqueous solutions consisting of these components were prepared and the refractive index was measured at 20 °C and each component was studied both alone and in mixtures with the others. The refractive index of white dry wines samples was also measured. A linear regression analysis was performed and linear multi-dependence equations were derived. The resulting regression models had a coefficient of determination over 97.3%. Glucose/fructose was found to have the greatest effect on the refractive index, followed by tartaric acid and glycerol while ethanol had the smallest effect. The knowledge of the correlation of the concentration of each wine component to the refractive index can be of value for the estimation of fermentation kinetics.

Effect of ethanol, glycerol, glucose and tartaric acid on the viscosity of model aqueous solutions and wine samples.

Viscosity is a property that exerts great influence on the body of wines, since it affects the sensation of thickness in the mouth. The present study refers to the quantitative correlation of the major components of wine, alcohol, reduced sugar, glycerol and total acidity, in its viscosity. Various model aqueous solutions consisting of these components were prepared and viscosity was measured at 20 °C. Each component was studied either alone or in mixtures with the others. Viscosity of white dry wines samples was also measured. From the experimental results, linear multi-dependence equations were derived, which correlate the viscosity with the concentration of the components of the solutions, each of them alone and in combination. Glucose was found to affect viscosity of model aqueous solutions the most, whereas ethanol had the least effect. The knowledge of these factors may have a practical value in optimizing wine's body.