The expected haze-free shelf life of beer is best determined by employing so-called forced aging methods.
Suitable for all beers
Forced aging is the most practical means for determining the duration of shelf life and the potential for haze formation in beer. In the forced aging test, an appropriate number of bottles (at least five) are subjected alternately to temperatures of either 40 °C (untreated beer) or 60 °C (stabilized beer) and 0 °C until the turbidity increases by > 2 EBC formazin units as a result of forced aging.
By multiplying the value determined in performing the test, expressed in ‘days of shelf life at 40 °C or 60 °C’, by a factor specific to beer (conversion factor), it is possible to predict how long a beer will remain free of turbidity or haze in the package.
Determination of the high-molecular weight proteins in wort and beer by precipitating them with magnesium sulfate
This method is suitable for wort and beer.
The high molecular weight proteins are precipitated by magnesium sulfate, and the nitrogen content in the sediment is determined, e.g., according to Kjeldahl.
In order to measure the portion of the high molecular weight protein fractions in wort and beer, precipitation with magnesium sulfate is recommended. Through gel chromatography it has been established that magnesium sulfate precipitates nitrogenous compounds possessing molecular weights of approximately 2600 Da and higher [2]. A strong correlation between the nitrogenous substances precipitated by magnesium sulfate and beer foam has also been observed [3, 4].
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.
This method describes how the protein content in adjuncts is determined.
This method describes how the protein content in adjuncts is determined.