[Quantitative determination of the protein content of milk by ultraviolet spectrophotometry. 3. The protein content of whole milk].
It is possible to determine the protein content of unskimmed milk after dilution with a detergent solution by measuring of absorbance at 210 and 220 nm. If milk samples are not elder than 36 h the difference A210-A220 shows a high correlation to the values of Kjeldahl nitrogen analysis (r = 0.97). Similar coincidence was found to the values of absorbance measurements in skimmed milk (A210: r = 0.98; A235-A280: r = 0.96). With decreasing age of unskimmed milk samples the coincidence diminished. Absorbance data measured at 210, 215, 220, 225, 235 and 280 nm as well as the differences A215-A225 and A235-A280 do not much agree with analogous results from skimmed milk. Elderly creamed milk samples allow the determination of protein content from milk plasma. It could be proved by Kjeldahl nitrogen analysis, that differences in the nitrogen content of unskimmed and skimmed milk depend on the nitrogen-loss during centrifugation, on the protein content and the protein-fat-ratio.
Akademie der Landwirtschaftswissenschaften der DDR, Forschungszentrum für Tierproduktion Dummerstorf-Rostock, Bereich Züchtungsforschung, Abt. Rinderzucht, Clausberg.
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Reichardt
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Schüler
D000818:Animals; D002417:Cattle; D008894:Milk Proteins / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet
D008894:Milk Proteins
Die quantitative Bestimmung des Proteingehaltes der Milch mittels Ultraviolettspektralphotometrie. 3. Mitt. Versuche zur Analyse des Proteingehaltes von Vollmilch.