Name (also glycerol or propanetriol) for a colourless, syrupy, trivalent type of alcohol. It is produced as a primary and valuable by-product mainly at the beginning of alcoholic fermentation, above all by wild, vineyard yeasts. This means that spontaneous fermentation usually results in higher amounts of glycerol. In controlled fermentation with artificial yeasts, the ratio of glycerol to ethanol (the most common type of alcohol in wine) is about 1 to 12. The higher the alcohol content, the higher the proportion of glycerol. The name is derived from the Greek "glykos" (sweet), as the substance tastes slightly sweet. However, it has only a minor influence on the sweetness of a wine. A high content causes a positively evaluated viscosity (thick liquid) in the wine. That is why glycerine is also colloquially called "oil sweet".