Infrared Analysis of Milk: Effect of Homogenizer and Optical Filter Selection on Apparent Homogenization Efficiency and Repeatability

Abstract

The apparent homogenization efficiency (AHE) and repeatability of one instrument was measured with 5 instrument homogenizers that differ in true homogenization efficiency (THE) to determine if instrument characteristics change when different fat A and B optical filters are used in the same machine. Inefficient homogenizers demonstrated both poor repeatability and poor AHE with both sets of fat B filters. One set of fat A filters produced infrared readings that were influenced less by differences in homogenization efficiencies than the other set. The most inefficient homogenizer demonstrated poor repeatability and failed AHE evaluation with both pairs of fat B filters and one pair of fat A filters. Differences in the transmission characteristics of the 2 sets of fat A filters influenced results of AHE evaluation for the most inefficient homogenizers. However, a very efficient homogenizer passed evaluation of AHE and demonstrated good repeatability on both unhomogenized and homogenized milks regardless of differences in the spectral characteristics of filters. A second objective was to determine if AHE test values are correlated with true differences in milk fat globule (MFG) size distribution. A good correlation was found between AHE and THE data for a group of homogenizers for one reference milk. A weakness of the AHE tesl is that the MFG size distribution of the externally homogenized reference milk may vary from one evaluation to another, resulting in an inconsistent reference point for AHE values. The preferred method of evaluating homogenization efficiency of infrared milk analyzers is analysis of the MFG size distribution resulting from instrument homogenization of unhomogenized milk.