Lesson 5 - Beer Haze SAQ
This lesson enables you to test yourself on the material covered in the lesson on Beer Haze and to determine the level to which you have met the learning outcomes.
Suggested Response - Q4
** Explain the principles and practice of beer haze measurement. Detail any shortcomings with the methodology used.
Response:
Brewers use the principle of light scattering to measure haze, called nephelometry. When illuminated by a light source, haze particles in the beer scatter light. By measuring the intensity of scattered light at a specific angle to the incident-light, and against a direct-beam light, we can quantify the haze into a number.
Most haze meters measure 90° scattered light, but some measure 11, 13 or 25 degrees forward-scatter measurement.
The 90° is good at measuring small haze particles and the 11, 13 or 25 degrees are good for larger particles, for example, yeast cells, diatomaceous earth and calcium oxalate crystals.
The haze meters are calibrated using formazin, a stable synthetic particle colloidal mixture with a defined particle size of 2.1 µm.
Before use, the meter is zeroed by using a filtered water blank sample.
There are some shortcomings with modern haze meters:
a. Firstly, different meters use different angles of scatter to measure haze. All use 90°, but the forward-scatter angle differs. This makes absolute haze comparison between centres difficult.
b. The light source wavelength is not standardised across analytical bodies. The EBC wavelength is not specified, and the
ASBC use 580 nm. This can lead to differences in result between measurements.
c. The relatively large particle size in the formazin standard used for calibration leads to an overestimation of the haze reading in certain so-called ‘invisible’ haze. These hazes appear visually bright but give high 90° readings. The haze is from very small particles of < 0.1 µm, made up of components originating in unmodified regions of the starchy endosperm of barley, retrograded starch and polysaccharides originating from yeast cell walls.
Despite these limitations, modern meters offer a quick and easy method of measuring beer haze, which usually correlates well to an observed lack of clarity in beer.