Glycerol

glycerol or glycerine, member of the chemical class of polyols and a minor product of alcoholic fermentation. The name derives from the Greek word for sweet and glycerol does indeed taste slightly sweet, as well as oily and heavy. It is present in most wines in concentrations ranging from about 4 to 6 g/l, although botrytized wines may have concentrations of around 10 g/l.

Glycerol does have a slight effect on the apparent sweetness of a wine but, contrary to popular conception, glycerol makes only a very minor contribution to the apparent viscosity of a wine, and bears no relation to the tears observed on the inside of many a wine glass. Whereas sensory tests have demonstrated that glycerol imparts sweetness at a threshold of about 5.2 g/l in white wine, a level of more than 28 g/l would be needed before any difference in viscosity were noted.