Fluorescence-Scatterometric Method for Measuring the Percentage of Dispersed Components of Emulsions as Applied to Assessing the Quality of Milk

A technique combining measurements of light scattering (scatterometry) and fluorescence (fluorometry) for determining the percentage of emulsion flowing within an optically transparent cylindrical tube is proposed. Based on this technique, a flow-through sensor is developed, whose workability is experimentally tested by the example of milk. The sensor operating principle is based on measurements of the angular distribution of scattered radiation of a semiconductor laser with a wavelength of 532 nm and the milk fluorescence intensity upon excitation by an UV light-emitting diode at a wavelength of 280 nm using an axial photodiode array. It is experimentally shown that the light scattering indicatrix in milk is shaped as a monotonic dependence of the scattering intensity on the fat percentage in the range of ~0.01–10%. Furthermore, the intensity level at forward scattering angles (0° < θ < 40°) is sensitive to large-scale particles in milk. The dependence of the fluorescence intensity on the protein content was found.