This wine defect, also known as bacterial cloudiness, is caused by a non-sterile bottling process in which yeasts are still present in the wine (a single cell is sufficient). The residual sugar present causes secondary fermentation and the formation of carbonic acid. This can also lead to the cork being expelled or even the bottle bursting. The wine has a cloudy colour with gas bubbles and a foamy edge on the surface. The taste is tangy and unharmoniously acidic with typical fermentation aroma.