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Urea Extraction Technique for Preparation of Whole _s and ß-Caseins

Agricultural Products Utilization Biochemistry, Department of Animal and Range Sciences, Montana State University, Bozeman

ABSTRACT

The following urea extraction technique has been used in our laboratory for preparation of whole _s,-casein (_{s1, 2, 3} and ₄) and ß-casein. This technique is simple, convenient, and gives good yields for these casein fractions.

Preparation for whole _s-casein. Whole isoelectric casein is prepared according to the method reported by the author (1). The excess moisture is removed by pressing it into a bag made of four layers of cheese cloth. The wet casein particles from three liters of skimmilk (75–85 g of dried casein) are then blended in an electric blender for 2 min, to break it up into small particles of homogenous size. The casein is then divided into 30-g portions and placed into 250-ml centrifuge bottles. To this is added 150 ml of a 4.80 M urea solution containing 21.20 g NaCl/liter. The bottles are then shaken onto a mechanical oscillating shaker for 25 min and centrifuged at 2,000 x g for 15 min.