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Abstract
The functionality of caseins in food systems depends on their solubility. The solubilities of whole casein, αs1-casein, β-casein, and dephosphorylated whole casein were measured as the pH was adjusted from 7 to 2 with HCl. When NaCl was added before pH adjustment, solubilities of whole casein at pH 2.5 decreased by 25, 40, 85, and 98% at NaCl concentrations of .01, .05, .1 and .2 M, respectively. Likewise, solubilities of dephosphorylated whole casein decreased by 50%, αs1-casein by 30%, and βcasein by 90% in .1 M NaCl. When .01 and .05 M NaCl were added to whole casein solutions after pH adjustment, effects on solubility were slight; however, . 1 and .2 M NaCl decreased solubility by 30 and 95%, respectively. When NaCl was added to casein solutions, pH decreased if the original solution was above the isoionic point, indicating Na ion binding; however, at pH between 5 and 3, the pH of the solution increased when NaCl was added. The pH shift upon addition of NaCl to dephosphorylated casein was less than with native caseins, suggesting that Na ion binding by phosphate and acid groups occurred in casein. Although NaCl is commonly used in food processing, these unusual solubility effects should be considered be considered when NaCl is used with casein.
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References
- Removal of phosphate groups from casein with potato acid phosphatase.Biochim. Biophys. Acta. 1976; 429: 448
- Physical Biochemistry.John Wiley & Sons, Inc., New York, NY1943
- Studies on the binding of small ions in protein solutions with the use of membrane electrodes. VII. The binding of the alkali-metal ions in solutions of phosphoproteins.Arch. Biochem. Biophys. 1958; 77: 158
- Emulsifying properties of pure and mixed αs1- and β-casein fractions: effects of chemical glycosylation.J. Agric. Food Chem. 1991; 39: 1369
- Covalent binding of glycosyl residues to bovine casein: effects on solubility and viscosity.J. Agric. Food Chem. 1989; 37: 32
- Proteins Structure and Molecular Properties.W. H. Freeman and Co., New York, NY1984
- Data for Biochemical Research.3rd ed. Oxford Univ. Press, Oxford, Engl1986
- Physical equilibria: proteins.Fundamentals of Dairy Chemistry. 3rd ed. Van Nostrand Reinhold Co., New York, NY1988 (Page 470)
- Caseins.Food Gels. Elsevier Sci. Publ. Co., Inc., New York, NY1990 (Page 128)
- Interaction of bovine αs1-casein with small ions.J. Am. Chem. Soc. 1965; 87: 110
- Physicochemical and dynamic properties of caseins modified by chemical phos-phorylation.J. Food Sci. 1992; 57: 617
- Functional properties of αs/κ- or β-rich casein fractions.Food Chem. 1991; 39: 211
- Binding of calcium ion to bovine β-casein.J. Dairy Res. 1981; 48: 71
- The search for standardized methods for assessing protein functionality.Developments in Food Proteins-5. Elsevier Sci. Publ. Co., Inc., New York, NY1987 (Page 302)
- Effects of salts on the solubility of casein and paracasein.J. Dairy Sci. 1936; 19: 573
- Qualitative and quantitative determination of caseins with reverse-phase and anion exchange HPLC.J. Food Sci. 1991; 56: 1415
- Method for the colorimetric determination of phosphorus.Science (Washington, DC). 1944; 100: 413
- DEAE-cellulose-urea chro-matography of casein in the presence of 2-mercaptoethanol.J. Dairy Sci. 1966; 49: 792
Article info
Publication history
Accepted:
January 10,
1994
Received:
January 19,
1993
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Copyright
© 1994 American Dairy Science Association. Published by Elsevier Inc.
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