Mathematical Model Describing the Relationship of Fat, Protein, and Lactose to the Total Solids—Its Application in Milk Testing

Abstract

California dairy farmers producing and selling Grade A milk for pasteurization receive payment based on milkfat and solids-not-fat content of raw milk. In 1970, the concept of using electronic methods for testing of milk and its components was accepted by the California Department of Food and Agriculture. The InfraRed Milk Analyzer (IRMA) with its ability to measure fat, protein, and lactose, using a predetermined factor for the unmeasured solids, appeared to fill the need for a rapid, accurate, and economical method. After comparing IRMA results with chemical tests of known accuracy for several seasons, it appeared the ash factor could vary seasonally and geographically, as well as with individual dairy herds. It was decided to study the accuracy and calibration stability of InfraRed Milk Analyzers (IRMA), as well as the use of a constant value for the ash factor. By applying a multiple regression technique to milk sample data, it was possible to generate a model describing the relationship of fat, protein, and lactose to total solids (and solids-not-fat).