Karien’s comments on the hype that was made about glycerol, makes me nostalgic. Everybody was caught in the frenzy to find ways to increase glycerol in wines, and people went to extremes to achieve their goal.

 Glycerol is one of the base chemicals used to make dynamite, and the commercial production of glycerol involves yeast fermentation, where SO2 is added constantly. To protect itself from the SO2, yeast produces glycerol. Winemakers tried to simulate this effect by stressing the yeast during fermentation. Treatments included adding small amount of SO2 constantly during fermentation, adding unfermented juice to wine (osmotic shock) and stressing the yeast by cooling it suddenly. Many winemakers (and some of the best) practised fermentation practices where the must was cooled to 10°C, allowed to rise to 15°, cooled quickly to 10°C, allowed to warm etc, to increase the amount of glycerol in the wine.

 All these techniques probably resulted in an increase in the glycerol concentration, but had no effect on quality resulting from the glycerol.

Louis Nel is the owner and winemaker of Louis wines in South Africa.