Phenolic compounds originate in malt and hops. The amount of these compounds present in the finished beer is largely dependent on the technology and equipment used to brew the beer. The structure and size of the molecules determines to what extent they affect the various attributes of the finished beer, such as color, flavor, flavor stability, foam as well as chemical-physical stability. Under less than optimal conditions, for instance given a high concentration of compounds with a proclivity for polymerization, condensation or the presence of air (oxygen), the resultant compounds with the ability to precipitate proteins, possess an undesirable flavor.
Tannoids belong to the type of polyphenols, which can be precipitated with PVP and include the lower to medium molecular weight polyphenols, polymers of catechins and anthocyanogens. Tannoids are present in malt and hops. Although they are present in relatively small amounts in beer, tannoids are of great significance for the colloidal stability and flavor consistency of the beer. They can effect precipitation of the proteinaceous substances found in wort and beer but can also serve as protective compounds.
This method is suitable for barley, malt, hops, wort, beer and other beverages
The tannoid content of beer and wort as well as the content in barley, malt and hop extract can be determined through precipitation with polyvinylpyrrolidone (PVP), which has a structure similar to protein in that tannoids attach to it by means of hydrogen bonds. As a result, PVP and tannoids form insoluble complexes, which produce turbidity. If PVP is continuously metered into the sample, the turbidity will constantly increase until all of the tannoid molecules are attached to the PVP; however, if the PVP continues to be added to the sample after that point, then the turbidity will begin to decrease. The quantity of PVP required to reach the maximum level of turbidity is proportional to the tannoid content. The Tannometer, therefore, measures the turbidity relative to the quantity of added PVP and expresses the tannoid content of the sample in mg/l of PVP.