Determination of the total oxygen content (dissolved and in the headspace) in filled containers
The bottled or canned beer is brought to 20 °C and mechanically shaken, thereby achieving equilibrium between the oxygen dissolved in the beer and the oxygen present in the headspace (Henry’s and Dalton’s laws). By directly measuring either the oxygen in the beer or in the headspace, the total oxygen can be calculated through referencing a table of values, which includes the headspace volume as a percentage of the fill volume.
Cloudy beers
The shelf-life test involves direct incubation of the untreated, sealed sample with accompanying visual inspection of the biological states of a beverage (slime formation, creamy skin, agglomerates) and a final microscopic analysis.
Filtered beer
Testing for microbiological shelf life involves direct incubation of the untreated sealed sample as well as a visual inspection of the biological condition of a beverage (medium) and a final microscopic analysis in the event of positive visual findings.
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.
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.