After longer periods of storage, filtered beer loses its clarity and brilliance, especially when it is cooled, to the point that haze or a sediment layer forms in the beer. In order to eliminate sensitivity to cold and to avoid undesirable haze or turbidity, beer is often treated with clarifying agents, which allow beer to remain free of haze for months longer than it would without such treatment. Because it is valuable to gain some insight into the stability of packaged beer as early as possible, methods of analysis have been developed that provide information immediately after the packaging process regarding the propensity of a beer to form haze.
This method allows a prediction of the expected permanent turbidity of the beer.
Suitable for all beers.
Strong supercooling causes reversible turbidity in beer, which depends on the condition of the beer and is caused by precipitated polyphenol-protein complexes. The addition of alcohol reduces the solubility of the complexes and thus accelerates the formation of turbidity.
The cold test, which can be performed very quickly, allows predictions to be made about the expected permanent turbidity of the beer. Immediately after filtration or bottling, the AKT provides indications of the turbidity potential of a beer and the effectiveness of stabilization measures, which can then be evaluated and modified if necessary.
The influence of oxygen is not recorded by the test.
Beer is cooled strongly (to -8 °C) in a cuvette with the addition of alcohol (up to 6 %) (down to -8 °C). The turbidity formed in a specified time (40 min) is measured (EBC formazin units).