Today in 1998, US Patent 5716850 A was issued, an invention of Gurinder Takhar and Mandy King, assigned to Whitbread PLC, for their “Monitoring the Colour And Bitterness of Beer.” Here’s the Abstract:

A method of determining one or both of the colour and bitterness of beer by illuminating the beer with light of a pre-determined wavelength, typically 400±30 nm, to cause iso-α-acids in the beer to fluoresce. The fluorescence is detected over a range of wavelengths, typically 420 to 673 nm, using a fluorescence spectrophotometer. One or both of the colour and bitterness of the beer is determined by comparing an output signal from the fluorescence spectrophotometer to output signals stored for beers of known colour and bitterness.