Performance of Homogenizers in Infrared Milk Analyzers: A Survey

Abstract

Abstract The objective of this survey was to determine if infrared milk analyzers can achieve a <0.05% difference in fat test between unhomogenized and homogenized portions of the same milk, as stated in official methods. Two batches of pasteurized, unhomogenized milk (3 and 6% fat) were prepared from a single source of raw cream and skim. Homogenized milks were produced at 3 pressures: 0, 10342, and 17238 kPa. Pairs of unhomogenized and homogenized portions of the same milk were tested on 22 infrared analyzers. More instruments exceeded the 0.05% difference between homogenized and unhomogenized milk than expected; differences between homogenized and unhomogenized milk increased with increasing homogenization pressure and fat concentration. At 3% fat, differences between homogenized and unhomogenized milks at both 10342 and 17238 kPa were <0.05% for 21 of 22 instruments for fat A; only 17 and 13 of 22 instruments for fat B achieved a difference of <0.05% at 10342 and 17238 kPa, respectively. At 6% fat, differences between homogenized and unhomogenized milks for fat A were <0.05% for 15 and 14 of 22 instruments at the 2 pressures, respectively. For fat B, 8 and 5 of 22 instruments achieved a difference of <0.05% at 10432 and 17238 kPa. Instruments were also evaluated for homogenization efficiency by a revised criterion that is dependent on the fat content of the samples used for the evaluation.