Infrared Milk Analysis — Challenges for the Future

Infrared milk analyzers are the only practical method of economically testing large numbers of milk samples for fat, protein, and SNF content in producer payment and dairy herd improvement programs. The major challenge for successful use of infrared analyzers is correctly establishing and maintaining accurate calibration. To achieve an accurate calibration, an infrared analyzer needs to be checked periodically to verify that zero drift, repeatability, purging efficiency, lineaxity, and homogenization efficiency meet minimum instrument performance standards. Once these performance criteria have been satisfied, the primary slope for each channel can be established and maintained. Next, intercorrection factors for each component need to be determined. Two different approaches are used to determine intercorrection factors for an instnunent: characterization with reference solutions or multiple regression of uncorrected instrument data versus chemical data on large numbers of milk sampies. The comparative ruggedness of these two approaches has never been collaboratively studied. Finally, secondary slope and bias for day-to-day adjustment of calibration are established. In instruments with both fat A and B filters, the ratio of these signals used for fat determination needs to be set. Various ap-