Fat emulsion. Effect of heat on solubility of hydrophilic emulsifiers

Abstract

SummaryThe bonds between some water‐soluble emulsifiers and water are hydrogen bonds with low energies of dissociation, of the order of 7 kcal./mole. In the absence of other factors such bonds can be broken by the kinetic energy of motion at elevated temperatures.The solubility of several emulsifiers was determined, and emulsions containing these emulsifiers at concentrations 2 to 4 times the amount required to make a monomolecular film of the oil droplets were made.To provide emulsion stability at homogenization and sterilization temperatures the emulsifiers must be more hydrophilic than many oil‐in‐water emulsifiers that are satisfactory in ordinary use and must have an increased affinity for water in the temperature range of 5° to 120°. For a given type of emulsifier containing a given alkyl group, an optimum weight percentage of polyoxyethylene groups is required.The solubility of an amine type emulsifier with the same alkyl group and approximately the same weight percentage of polyoxyethylene groups per molecule is greater than that of the corresponding amide compound, which, in turn, is more soluble than the corresponding ester type of emulsifier, because of differences in chemical type. Polyethylene‐propylene oxide had the longest solubility range of the emulsifiers tested.An increase in particle size or an appearance of two phases in emulsions prepared with emulsifiers which undergo solubility inversion below 85° was found. Emulsions prepared with emulsifiers whose inversion temperatures were above 85° maintained, generally, a low particle size on autoclaving, did not separate into a watery phase and an emulsion phase, and did not form a layer of oil.Emulsions prepared with two emulsifiers, such that one had some lipophilic characteristics stronger than the other, were found to be stable and maintain a low particle size on autoclaving.