On Reflectometric Measurement of a Refractive Index of Milk

The refractive index of milk samples was measured with a reflectometer. Fresnel's formula for intensity reflectance and the concept of critical angle were applied to measured data. Milk samples were also measured with surface plasmon resonance sensor for refractive index assessment. The experiments were carried with commercial milk that had fat volume concentrations of 0.004, 1.53, and 3.55%. We observed that simultaneously quantitative information about the refractive index and absorption of milk, as a function of fat concentration, could be obtained with both devices.