Acta Univ. Agric. Silvic. Mendelianae Brun. 2010, 58, 123-136
Published online 2014-08-06

Analysis of calibration results for casein determination via indirect method of infrared spectroscopy

Oto Hanuš1, Tao Yong2, Josef Kučera3, Václava Genčurová4, Kristýna Hanušová4, Tomáš Kopec3, Jaroslav Kopecký1, Radoslava Jedelská4

1Research Institute for Cattle Breeding Rapotín, Výzkumníků 267, 788 13 Vikýřovice, Czech Republic
2Anhui Agricultural University, Department of Animal Sciences, College of Animal Science and Technology, Changjiang West Rd. 130, 230036 Hefei, P. R. China
3Czech Fleckvieh Breeders Association, Horní 28, 591 01 Žďár nad Sázavou, Czech Republic
4Agriresearch Rapotín, Výzkumníků 267, 788 13 Vikýřovice, Czech Republic

Casein measurement is important for cheesemaking and control of dairy cow nutrition. Reference Kjeldahl method is not suitable for routine purposes. Infra-red spectroscopy MIR and MIR-FT use can be a solutin. However, their casein specifity is relatively limited. Aim of the work was to assess the quality of performed calibrations for validation of calibration parameters. A retrospective analysis of MIR and MIR-FT calibrations was performed for estimation of limits their suitable parameters. Mean casein values of reference sample sets varied from 2.49 to 2.7% (2.61 ± 0.155). Mean variation range was 0.561 ± 0.164%. The mean correlation coefficient of calibration (KKK) was 0.974 ± 0.018 (P < 0.001). The mean standard deviation of mean for individual differences (SDID) was 0.03 ± 0.011% (from 0.01 to 0.08). MIR-FT results were slightly better both for calibration and for proficiency testing. The high and low KKKs were higher in the case of accepted calibration as in proficiency testing for MIR-FT and MIR (0.986 > 0.964 and 0.970 > 0.948; 0.982 > 0.947 and 0.947 > 0.911; P < 0.001). The casein number varied from 79.4 to 80.56% in bulk milk samples in three years, its variability was low from 1.4 to 1.5% relatively, which shows on relatively reliable casein analyses by methods MIR and MIR-FT. It does not need to agree fuly for individual milk samples. It is linked more to MIR than MIR-FT. Limits for acceptable calibration parameters were derived: > 0.945 for KKK; 0.048 for SDID and 0.029% for mean difference as maximum.


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