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.
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.