Kolbach Index is a measure of the extent of protein modification in beer. It comprises the assessment of total soluble protein in wort as a percentage of the total protein measureable in the malt. This assessment is as performed in the Congress mash.
The typical value for the Kolbach index in suitably modified malt is between 38% and 42%. Various claims are made concerning the relationship of this parameter to quality aspects of beer such as haze stability and foam. The reality is that the index is nothing more than a gauge of the extent to which proteolysis has occurred during malting.