Modeling the Joint Influence of Milk Fat Particle Size Micro-Distribution and Absorption on Optical Scattering and Composition Determination

Optical scattering techniques often lead to simplified assumptions about secondary factors, such as neglecting the absorption effect of particles or the residual particle size micro-distribution after homogenization; these are made to enhance measurement efficiency. However, such simplifications can introduce systematic errors in precise detection. This study uses the scattering–transmission ratio composition determination method as an example, revises the basic scattering–transmission ratio model to incorporate absorption effects, and demonstrates the coefficient calculation process. Furthermore, Mie key coefficients, including the particle size micro-distribution—which are core parameters of this method—are derived. Based on these models, effective particles from image processing are analyzed to assess the impact of these two factors. The results demonstrate the joint influence of the micro-distribution and absorption characteristics of milk fat particles on Mie key coefficients and composition determination, exhibiting non-uniform enhancement and reduction effects. Specifically, at a wavelength of 800 nm, the scattering–transmission ratio of the modified model increases by a factor of 1.56 compared to the traditional model at a volume concentration of 0.5%, while at 3.3% concentration, the scattering–transmission ratio of the modified model is approximately one-third of the traditional model. These findings provide a theoretical basis for developing dairy product quality assessment technologies.