An absolute prerequisite for a high-quality wine is controlled fermentation. During alcoholic fermentation, the sugar contained in the grape must is converted into alcohol, whereby various primary and secondary by-products are also produced. These are, for example, the components ester and glycerol, which are positive for the taste of the wine. Depending on their concentration, the various chemical substances can negatively influence the quality of the wine through fermentation errors. Most fermentation faults can be avoided by appropriate must treatment. For example, sulphurisation of the grapes and a correctly dosed degumming of the must (removal of trub particles) are common. Fermentation stagnation can have physical (low fermentation temperature), microbiological (beginning BSA during fermentation) or chemical (low nitrogen content in the must) causes. The stagnation manifests itself through very typical signs. Carbon dioxide formation stops, the temperature drops and the yeasts begin to settle at the bottom.