Detection of adulteration of pasteurised milk with whey by determination of the casein-bound phosphorus and protein nitrogen content.
A new method to detect the adulteration of pasteurised milk with whey is described. The method is based on the determination of casein-bound phosphorus (Pcas) and the protein nitrogen content in milk. By using a mean Pcas content (0.85 g P/100 g casein), a Kjeldahl factor of 6.34 and protein N, the relative casein-N content (casein N/protein N x 100) can be estimated. Over a period of one year the variation in the phosphorus factor of dried skimmed milk samples amounted to 2.9%. In order to calculate the percentage of added whey, a standard curve has been prepared in which the relative casein content is plotted against the corresponding whey percentage. The results of 26 analyses on genuine pasteurised milk (Pcas = 21.7 mg/100 ml; casein N/protein N = 80.9%) and on 25 whey samples were used for the standard curve. In laboratory-made blends of pasteurised milk and cheese whey (5%, 10%, 20% and 30%), the estimated percentage of whey varied between -1.2% and +2.9% from the actual value. The analysis of nine samples from the Brazilian market showed that four samples were clearly adulterated with cheese whey. Sweet and/or acid whey addition will be detected by the proposed method.
Wolfschoon-Pombo
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AF
Instituto de Laticínios Cândido Tostes/EPAMIG, Minas Gerais, Brazil.
Furtado
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MA
D000818:Animals; D002364:Caseins / Q000032:analysis; D003611:Dairy Products / Q000032:analysis; D005506:Food Contamination; D007785:Lactose / Q000032:analysis*; D008892:Milk / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D012621:Seasons
D002364:Caseins; D010758:Phosphorus; D007785:Lactose; D009584:Nitrogen