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.
Hops with high moisture content have a shorter storage life; in contrast, hops that are too dry disintegrate easily and lose their lupulin.
Hops and hop products intended for use in beer brewing or elsewhere in the food industry
The moisture content of whole hops, hop powder products or pellets is determined through the difference in weight before and after drying under standardized conditions.
Suitable for analysis of all (laboratory) wort samples
Iron is measured using the AAS technique by directly aspirating the diluted sample into an acetylene oxygen flame or electrothermally (graphite furnace); the measurement is made at 248.3 nm.
wort, beer
The thiobarbituric acid index is a measure of the cumulative thermal stress brought about by exposure to heat (intensity) in malt and wort. The TBI is a figure, which indicates the presence of numerous Maillard reaction products in addition to 5-hydroxymethylfurfural (HMF) and other organic compounds.
The analysis sample (e.g., wort, beer or wort obtained from a standardized method, such as Congress wort) undergoes a chemical reaction with an acetic acid/thiobarbituric acid solution; the resulting product is yellow in color and is measured spectrophotometrically.
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].
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.