Detection of adulteration of pasteurized milk with by determination of the casein-bound phosphorus and protein nitrogen content

Abstract

A new method to detect the adulteration of pasteurized 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/100g casein), a Kjeldahl fator 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 fator of dried skimmed milk smaples amounted to 2.9%. In order to calculate the percentage of added whey, a standard curve has been prepared in wich 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% form the actual value. The analysis of nine samples were clearly adulterated with cheese whey. Sweet and/or acid whey addition will be detected by the proposed method.    

Introduction 

Because it is economical, cheese whey (in its various forms) is a mean of increasing the volume of milk sold to the consumers by the fluid milk industry. In contrast to Europe and North America, where concern exists because of adulteration of non-fat dried milk with whey powder, illigal addition of whey to pasteurised mil kis na increasing problem in Latin America. Several procedures have been investigated in order to detect skim milk powder adulteration [1]: polarographic cysteine/cystine determination [1]; a colorimetric sulphur-based method [2, 3]; high pressure liquid chromatography (HPLC) of glycomacropeptide [4,5]; sialic acid determination [5 – 7]; microscopic observation [8]; amino acid analysis [9]; gel electrophoresis [10]; HPLC of indoxyl sulfate [11]; and one of above [6] simplified and adapted for the detection of rennet whey in Brazilian milk [12].

References   

1. LECHNER, E.; KLOSTERMEYER, H. Milchwissenschaft, v. 36, p. 267-270, 1981.

2. HILL, S. D.; RICHTER, R. L.; DILL, C. W. Cult Dairy Prod J., v. 22, p. 14-18, 1988.

3. DE KONNING, P. J.; VAN ROOIJEN, P. J. Milchwissenschaft, v. 26, p. 1-6,1971.

4. OLIEMAN, C.; VAN DEN BEDEM, J. W. Neth Milk Dairy J., v. 37, p. 27-36, 1983.

5. MEHRENS, H. A.; REIMERDES, E. H. GIT Fachz Lab., v, 30, p. 406-409, 1986.

6. DE KONNING, P. J.; EISSES, J.; DE VRIES, H. Neth Milk Dairy J, v. 20, p. 204-212,1966.

7. RAMPILLI, M.; RESMINI, P.; TRIPICIANO, C.; SADINI, V. Sci Tec Latt Cas, v. 36, p. 28-45, 1985.

8. LOKO, R. Tech Laitiere, v. 964, p. 23-27, 1982.

9. GREENBERG, R.; DOWER, H. J. J Agric Food Chem., v. 34, p. 30-32, 1986.

10. BASCH, J. J.; DOUGLAS, F. W.; JR PRONCINO, L. G.; HOLSINGER, V. H.; FARREL, H. M. Jr. J Dairy Sci., v. 68, p. 23-31, 1985.

11. WOLFSCHOON-POMBO, A. F.; KLOSTERMEYER, H. Z Lebensm Unters Forsch, v. 182. p. 103-106, 1986.

12. WOLFSCHOON-POMBO, A. F.; PINTO, A. P. E. de F. Cienc Tecnol Aliment, v. 5. p. 111-115, 1985.

 [100] WOLFSCHOON-POMBO, A. F.; FURTADO, M. A. M. Detection of adulteration of pasteurized milk with by determination of the casein-bound phosphorus and protein nitrogen content. Z. Lebensm Unters Forsch, v. 188, p. 16-21, 1989.