Valid for all non-turbid beers
By incrementally adding increasing amounts of a saturated ammonium sulfate solution to beer, haze appears as a result of protein precipitation. The amount of the ammonium sulfate solution necessary to produce haze is directly proportional to the stability of the beer. The ammonium sulfate precipitation value expresses the ml of saturated ammonium sulfate solution that must be added to 100 ml of beer in order to produce a barely perceptible opalescence.
The Esbach reaction test provides an indication of the physical and chemical stability of beer, particularly for those which have been treated with bentonite [1, 2].
Suitable for all non-turbid beers
Higher molecular weight proteins are precipitated with the Esbach reagent (solution of picric acid and citric acid). The haze that is formed is determined spectrophotometrically.