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Journal of Dairy Science Vol. 41 No. 4 465-471
© 1958 by American Dairy Science Association ®
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Effect of Calcium Chloride and Heat on Solutions of Mixtures of ß-Lactoglobulin and Casein

E. S. Della Monica, J. H. Custer and C. A. Zittle

Eastern Regional Research Laboratory,1 Philadelphia, Pennsylvania

ABSTRACT

The effect of heat and calcium chloride concentration on the precipitation in the ultracentrifuge of casein and ß-lactoglobulin has been studied. With ß-lactoglobulin alone (1% solution) at pH 6.5 with 2 mM calcium chloride per liter, the protein is totally precipitated after heating at 90° for 30 min. and ultracentrifuging (127,000 X G for 45 min.). With ß-lactoglobulin (1%) and casein (2%) together under the same conditions, no precipitate is obtained until the calcium chloride concentration exceeds 4 mM per liter. Electrophoretic examination of the supernatant solution, when 50% of the total protein is precipitated (8 mM calcium chloride per liter), together with the insolubility of the precipitate in versene, suggested that the ß-lactoglobulin is in the sediment. This conclusion was confirmed by the determination of the phosphorus to measure the casein distribution. Similar treatment of an unheated mixture showed that all of the ß-lactoglobulin was in the supernatant solution. Also determined was the amount of calcium bound to the precipitated proteins, both alone and mixed. The total results support the assumption that the proteins in the mixture studied react independently and not as a complex.

FOOTNOTES

1 A laboratory of the Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.






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Copyright © 1958 by the American Dairy Science Association ®.