Q: What quantitative method (or instrumentation) is used to measure light absorption, transmission, and reflection rates in food production in order to assign to assign a ‘color’ value?
A: Spectrophotometry measure light absorption and reflection rates. Colorimeter is also accepted.
Spectroscopic Studies of Food Colorings
Light is a wave (plus photons riding the wave) and as a wave, there are fluctuations in intensity and band shifts. UV/VIS spectrum (ultraviolet and visible wavelength range 10-780 nm). The roots of electronic color measurement Based on Lambert-Beer-Bouguer’s Law stating absorbance is proportional to concentration within a range when measuring monochromatic light through a homogenous solution.
Here is a vision of BBL based on electromagnetic theory: The Bouguer‐Beer‐Lambert Law: Shining Light on the Obscure – Mayerhöfer – 2020 – ChemPhysChem – Wiley Online Library
In the traditional French bakeries, bread is considered done when it is “broomstick brown.” Subjective color assessment is too inconsistent for commercial production, so today we use machine vision based on L.a.b. values, or RGB which is based on additive light theory. This is the same model that computer screens utilize, but different from the subtractive light model of CMYK that printers are based on. It is helpful for consumer visual appeal to adjust for the differences between digital color and printed color representations in packaging.
Colorimeter measures Red, Green, and Blue.
L = lightness, A= green to red, B= blue to yellow
Spectrophotometer works on the same principle, but usually has more than one light source (sometimes with multiple angles of light angles), and measures the full spectrum of visible light.
Hue, Saturation, Light
No matter how you see it, there’s a lot more to color than meets the eye.