Beer colour measurement started getting attention as far back as the late 1800’s. By 1950, methods were being developed by the Institute of Brewing, the American Society of Brewing Chemists, and the European Brewing Congress. As technology evolved in the brewing industry, many organizations began to adopt different methods to measure beer colour as compared to early visual standards.
Colour standards were originally developed for beer colour determination through a visual comparison of samples that ranged from 2 – 27. These visual standards were based on both beer colour intensity and hue. The low end of the scale was used for the pale (more) yellow colour/hue beers (lagers and pale ales) while the middle and upper end of the scale moved through the red beers to the brown (darker) stout type beers. The European Brewing Congress conceived a standard measure for beer colour known as EBC colour.
These methods were developed as spectrophotometric determinations. The European Brewing Congress used a spectrophotometric method that originally measured beer colour at 530 nm (526.6 nm in some cases). The Institute of Brewing (IoB) also uses the 530 nm measurement to determine beer colour. In contrast, the American Society of Brewing Chemists (ASBC) called for colour measurement at 430 nm. In 1991, the EBC adopted the 430 nm wavelength method using a 1 cm cuvette while the ASBC method called for a ½ inch cuvette. While any of these methods for beer colour measurement are fairly consistent and comparable, colour measurement of darker, more concentrated brewing extracts (caramel colour and malt extract) are not as straightforward.
IoB colour = Absorbance (530 nm) x D (dilution) x 1000
EBC (as EBC) colour = Absorbance (430 nm) x D (dilution) x 25
ASBC (as SRM = Lovibond)) colour = Absorbance (430 nm) x D (dilution) x 12.7
(Where EBC = SRM x 1.97)
Extrapolation of EBC colour values for dark extracts (Caramel or Malt) can be limiting unless a reference method and wavelength being used for measurement is indicated. Caramel colours can vary in intensity and hue depending on caramel class and strength. Darker caramels will have less yellow hue and a conversion factor is used for the IoB method of measurement (at 530 nm) to give a corrected colour. The four different classes of caramel colour each have their own conversion factor for IoB measurement.
Product Development Scientist