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Stability of Fluid Food Emulsions. II. Interacting Effects of Electrolytes, Sodium Caseinate and Emulsifiers¹

Department of Food Science and Nutrition, Ohio Agriculture Research and Development Center, Columbus 43210

ABSTRACT

Our first paper of this study dealt with single effects of protein, electrolytes, and emulsifiers on the stability of model emulsions. This second phase involved interactions of proteins, electrolytes, and emulsifiers in relation to protein-salt solubility and emulsion stability in complex multi-component fluid food systems, to develop stable fluid dairy-type foods.

Preliminary investigations of model aqueous systems of CaCl₂ and Na₂HPO₄ showed that the extent and nature of precipitated salts depended on their relative concentrations. In equimolar concentration (25 mM/liter, each) of the electrolytes, the precipitated salts were a mixture of CaHPO₄ and Ca₃ (PO₄)₂. Maximum precipitation occurred when phosphate to calcium was 2:1, the ratio at which precipitated salt conformed primarily to CaHPO₄. Addition of sodium citrate had a significant solubilizing effect, but precipitation of an apatite-type calcium-phosphate-citrate salt still occurred.

In fluid systems containing 4% emulsified coconut oil, 2% sodium caseinate and 25 mM/liter CaCl₂, added Na₂HP0₄ precipitated protein and calcium in increasing amounts up to 12.5 mM/liter of phosphate. At higher concentrations, phosphate favored solubilization of protein but it adversely affected calcium solubility and emulsion stability. Addition of sodium citrate to the system had a distinct solubilizing effect, but emulsion stability was impaired. Citrate at 7.5 mM per liter, completely solubilized protein and salts. Emulsion stability was restored with emulsifiers of Hydrophile-Lipophile-Balance (HLB) of 3 to 5, contrasted with an HLB requirement of 7 to 9 for the model o/w emulsion without caseinate and electrolytes. By judicious use of electrolytes and emulsifiers, completely stable fluid food systems were developed, containing the electrolyte balance of regular cow's milk.

¹ Approved for Journal Series Article 83: 71, The Ohio Agricultural Research and Development Center. Wooster.

² Present address: Fisher Cheese Company, Wapakoneta, Ohio.