A method for the rapid evaluation of colloidal stability in beer.
The principal disadvantage of the conventional forcing test for determining the colloidal stability of beer is the fact that it takes several days to produce a result. In order to overcome this problem, the author and colleagues evaluated 4 rapid test procedures, namely the saturated ammonium sulphate precipitation limit (SASPL), found by measuring the quantity of saturated ammonium sulphate solution which must be added to a beer sample to make its turbidity begin to increase; a simplified version where the difference in the turbidity of 150 ml beer at 21.1 degrees C before and 10 minutes after adding 30 ml saturated ammonium sulphate is measured; the Chapon test, where the turbidity of 200 ml degassed beer at 20 degrees C is measured before adding 14 ml of 95% ethanol, holding temperature at 20 degrees C for 20 minutes followed by 50 minutes at minus 5 degrees C, measuring turbidity again and comparing with the first measurement; and a simplified cooling test like the Chapon test except that no ethanol is used and the period at minus 5 degrees C is only 40 minutes. Although none of these proved satisfactory by itself, it was found that combining the results of the simplified ammonium sulphate test and the cooling test, using a simple mathematical formula, yields a figure corresponding much more closely to the results of the forcing test than either of these tests by itself, although a certain degree of adjustment may be necessary to allow for differing characteristics of individual beer types or brands. The author considers that the test should also be easy to automate.
Keywords : accelerated beer colloidal haze measurement stability