Abstract: Methods and apparatus are provided for measuring component concentration in a liquid containing relatively large particles and relatively small particles. The invention may be utilized for measuring fat and casein concentrations in a dairy product, but is not limited to such use. A polarized light beam is directed through a scattering cell having first and second windows and containing a sample of the liquid. A normal to an exterior surface of the second window of the scattering cell is at or near Brewster's angle with respect to the light beam to reduce or eliminate reflections. A first light detector, positioned at an angle of about 5° to about 45° with respect to the light beam, detects scattered light from a first component of the liquid, such as fat particles. A second light detector, positioned at an angle of about 130° to about 160° with respect to the light beam, detects scattered light from a second component of the liquid, such as casein particles.