Detection of Somatic Cells in Milk Using Laser Light Scattering

The angular intensity distribution of 650 nm laser radiation multiply scattered by bovine milk samples of various fat content, containing large-scale particles with a size of ~20 μm, is studied in cylindrical geometry. It is shown that the forward scattering intensity measured for milk with a fat content in the range of 0–6% decreases monotonically with increasing concentration of somatic cells in the range of 5 × 10⁴–10⁶ cm^‒3. However, the angular dependence of the side- and backscattering intensity, used to determine the fat content in milk, practically does not change when somatic cells are added. A prototype of a milk composition sensor is assembled, based on measuring the scattering indicatrix in the angular range of 18°–162° using an axisymmetric array of photodiodes in combination with a photodetecting CMOS matrix that measures the small-angle forward light scattering intensity (near 0°).