Near-infrared analysis of fat, protein, and casein in cow's milk

Fat, crude protein, true protein, and casein were determined in cow milks b y near-infrared transmission spectroscopy (NIR). Partial and overall PLS ca librations were performed on two sets of samples: partial calibration inclu ded 76 unhomogenized samples, whereas overall calibration used 96 homogeniz ed and unhomogenized samples. Standard errors of calibration were 0.12% for fat, 0.06% for crude protein, 0.04% for true protein, and 0.05% for casein in the overall calibration. Validation of the overall calibration with an independent set of samples gave standard errors of prediction of 0.07% for fat, 0.06% for crude protein and casein, and 0.05% for true protein. Except for fat, all of the statistical parameters were better with overall than w ith partial calibrations, which indicates that homogenization has an effect on NIR fat determination. Despite the relatively small number of samples i ncluded in the calibration model, NIR transmission was found to be a reliab le method for the determination of fat and nitrogenous constituents in milk .