The deterioration of a homogenizer’s mechanical components over time needs to be detected by the MIR operator to minimize the negative effect on analytical accuracy and repeatability. What causes MIR milk analyzers to have poor homogenization efficiency? There are 3 common problems for a 2-stage homogenizer designed with springs in the milk flow. First, if the coil spring has a rough spot on the end that is in direct contact with the ball it can chip the ball (Figure 4), preventing it to form perfect closure against the seat (Trout, 1950; Walstra et al., 2005). On this type of homogenizer the ball rotates, so the same area is not always contacting the seat, and the homogenizer performance may oscillate between getting better and worse depending on whether the place on the ball with the chip is contact with the seat. Second, because the spring is in direct contact with milk, pieces of foreign material present in milk and ball chips can get stuck in the spring, affecting homogenization performance and purging efficiency (Walstra et al., 2005). Third, if the spring is bent it can cause an unequal opening between the ball and the seat. When these things happen it is common to hear a high-pitched squeaking noise produced by the homogenizer. If the bent spring is allowing the opening between the seat and ball to happen only on one side, accumulation of material between ball and the seat will diminish homogenization performance.