At least two points in the processes of malt and wort production must be conducted in such a way that they bring about a higher level of thermal stress on the product, i.e., during the kilning of the green malt and when the wort is boiled. However, at these points, the thermal stress should be kept as low as possible in order to protect the flavor stability of the beer. Otherwise, an excessive amount of the substances serving as precursors for aging compounds are formed which can later be perceived when they exceed their respective flavor thresholds in the finished beer.
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.