The degree of turbidity present in a beer sample can be compared to beer containing EBC formazin standard solution for producing turbidity or haze through visual evaluation or determined with a device for measuring turbidity. The EBC scale is based upon a standardized formazin suspension. As an alternative, AEPA turbidity standard (styrene divinyl benzene suspension produced by Norit Haffmans, www.haffmans.nl) may be used. Clear, opalescent and turbid are the three levels of turbidity discernable by visual evaluation.
The turbidity of the beer is determined in order to evaluate how well the bottled beer can be stored and, if necessary, to predict the stability over time of the beer using the forced aging test
Turbidity measurement in beer
If a beam of light strikes a particle in a liquid, the light is scattered. This phenomenon is referred to as turbidity. In measuring turbidity during the lautering process, it has been shown that only light scattered in a forward direction should be measured to achieve a meaningful correlation between the concentration of solids and the measurement value. Measurements performed at a 90° angle do not correlate with the amount of solids in wort due to particle size and dependence on color. In addition to the amount of scattered light, the absorption (light transmission) is also measured. The utilization of dual beams eliminates disruptive parameters such as color, lamp age and window fouling.
For monitoring filter efficacy, measurements employing forward scattered light are advantageous (measured at an angle ranging from 11 to 25°).
With a suitable turbidity measuring device, the visual impression of turbidity is quantified.