title: Is it possible to screen for milk or whey protein adulteration with melamine, urea and ammonium sulphate, combining Kjeldahl and classical spectrophotometric methods?
abstract: The Kjeldahl method and four classic spectrophotometric methods (Biuret, Lowry, Bradford and Markwell) were applied to evaluate the protein content of samples of UHT whole milk deliberately adulterated with melamine, ammonium sulphate or urea, which can be used to defraud milk protein and whey contents. Compared with the Kjeldahl method, the response of the spectrophotometric methods was unaffected by the addition of the nitrogen compounds to milk or whey. The methods of Bradford and Markwell were most robust and did not exhibit interference subject to composition. However, the simultaneous interpretation of results obtained using these methods with those obtained using the Kjeldahl method indicated the addition of nitrogen-rich compounds to milk and/or whey. Therefore, this work suggests a combination of results of Kjeldahl and spectrophotometric methods should be used to screen for milk adulteration by these compounds.
authors.affiliation: Escola Politécnica de Saúde Joaquim Venâncio, Fundação Oswaldo Cruz, Av. Brasil, 4365, Manguinhos, CEP 21040-900, Rio de Janeiro, RJ, Brazil.
authors.forename: Virgínia de Lourdes Mendes
authors.initials: Vde L
authors.lastname: Finete
authors.forename: Marcos Martins
authors.initials: MM
authors.lastname: Gouvêa
authors.forename: Flávia Ferreira de Carvalho
authors.initials: FF
authors.lastname: Marques
authors.forename: Annibal Duarte Pereira
authors.initials: AD
authors.lastname: Netto
mesh_terms: D000645:Ammonium Sulfate / Q000032:analysis*; D000818:Animals; D002417:Cattle; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D005506:Food Contamination / Q000032:analysis*; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis*; D013053:Spectrophotometry / Q000379:methods*; D014227:Triazines / Q000032:analysis*; D014508:Urea / Q000032:analysis*; D000067816:Whey Proteins
chemical_list: D008894:Milk Proteins; D014227:Triazines; D000067816:Whey Proteins; D014508:Urea; C011907:melamine; D000645:Ammonium Sulfate
keywords: Ammonium sulphate; Melamine; Milk adulteration; Milk protein; Protein determination; Urea