Lipolysis and Proteolysis of Modified and Producer Milks Used for Calibration of Mid-Infrared Milk Analyzers¹

Calibration set mean FFA content during storage at 4°C for modified milk calibration sets for 28 d: (♦) set 1, (■) set 2, and (●) set 3; and producer milk calibration sets for d 15: (♢) set 1, (□) set 2, and (○) set 3.

Calibration set mean decrease in casein as a percentage of true protein (CN%TP) during storage at 4°C for (a) modified milk calibration sets for 28 d: (♦) set 1, (■) set 2, and (●) set 3; and b) producer milk calibration sets for d 15: (♢) set 1, (□) set 2, and (○) set 3.

Decrease in casein as a percentage of true protein (CN%TP) at the last day of shelf life as a function of SCC in (a) modified milk at d 28; and (b) producer milk at d 15.

Uncorrected reading residuals as a function of the increase in FFA content during 15 d storage at 4°C for the 2 producer milk calibration samples with the highest lipolysis from each replicate (6 samples total): (a) fat B, (b) fat A, (c) protein, and (d) lactose. Slope of residuals was different (P≤0.05) from zero for protein.

Uncorrected reading residuals as a function of the decrease in casein as a percentage of true protein (CN%TP) during 28 d of storage at 4°C for the 2 modified milk calibration samples with highest proteolysis from each replicate (6 samples total): (a) fat B, (b) fat A, (c) protein, and (d) lactose. Slope of residuals different (P≤0.05) from zero for fat B, fat A, and protein.