Quality Control of Technical Casein—Near Infrared Reflectance Spectroscopy Method

The near infrared (NIR) reflectance spectroscopy method can be used in the routine checking of the technical casein. All the chemical and physical characteristics of the product that influence the NIR spectrum affect the qualification. In order to monitor possible deviations in the preparation, it is advisable to carry out some test during the different manufacturing stages. These test are: determination of water, fat, ash, free and total acidity. A set of 66 ground casein samples was used to calibrate the output from NIR instrument InfraAlyzer 500 (Bran+Luebbe GmbH), taking reflectance readings every 2 nm between 1100 nm and 2500 nm. As soon as the spectral scanning had been completed, the casein samples were subjected to the standard wet chemistry analysis. The spectral data from this calibration set was then statistically manipulated using MLR method with the aid of the software SESAME ver. 2.10 (Bran+Luebbe GmbH) to generate calibration models. These calibrations were then applied to a separate set of 20 samples which, for validation purposes, were also analysed by wet chemistry. The casein samples analysis predictions compared with the wet chemistry results on these samples, with standard errors of determination of 0.1%, 0.2%, 0.2%, 0.2% and 0.5% for water, fat, ash, free and total acidity, respectively. The use of NIR instrumentation and appropriate calibrations is able to result in a significant saving of laboratory resources when large numbers of the technical casein samples are being processed for analysis.