A method of measuring the colour of beer, in units of the colour scales used by the American Society of Brewing Chemists and the European Brewery Convention, by photometric determination of the absorption of light at a wavelength of 430 nm (in the visible violet) under standardised conditions is described together with experiments aimed at developing an on-line sensor for the automatic continuous monitoring of the colour of piped beer by this method. The main problem with photometric colour measurement is that turbidity can distort the instrument reading so that the colour is recorded as being darker than is actually the case. (Likewise, dark beers can produce false positive readings on some turbidity sensors). It was found that the absorption loss at the infrared wavelength of 830 nm was practically unaffected by colour, and could therefore be used as a reference indicator of turbidity, enabling the colour reading to be automatically corrected.
Keywords : automatic beer calibration colour error measurement on-line photometry sensor turbidity