Calibration of Infrared Milk Analyzers: Modified Milk Versus Producer Milk¹

Flow chart of milk processing steps for manufacture of modified milk calibration samples. The gravity-separated cream, the 2× UF retentate, and the UF permeate are the end products that are used in combinations with water and lactose to formulate the modified milk calibration samples.

Residual plot of differences between instrument predictions and reference chemistry for Fat B for a) a modified milk calibration set expected calibration error, and b) a producer milk calibration set expected calibration error as a function of the predicted fat concentration.

Correlation of percent fat and protein content of a) producer milk calibration samples, and b) modified milk calibration samples used in Experiment 1.

Protein slope for an infrared analyzer calibrated with a) modified milk samples, and b) producer milk samples in Experiment 1 plotted as a function of study day. Filled (sets 1 and 3 for modified and sets 1, 3, 5, and 7 for producer) and empty symbols (sets 2 and 4 for modified and sets 2, 4, and 6 for producer) represent alternating calibration sets in a series.

Protein intercept for an infrared analyzer calibrated with a) modified milk samples, and b) producer milk samples in Experiment 1 plotted as a function of study day. Filled (sets 1 and 3 for modified and sets 1, 3, 5, and 7 for producer) and empty (sets 2 and 4 for modified and sets 2, 4, and 6 for producer) symbols represent alternating calibration sets in a series.

Protein slope for an infrared analyzer calibrated with a) modified milk samples, and b) producer milk samples in Experiment 2 plotted as a function of study day. Filled (sets 1 and 3 for modified and set 2 for producer) and empty (set 2 for modified and sets 1 and 3 for producer) symbols represent alternating calibration sets in a series.