SUMMARY A simple method was developed for estimating the emulsifying capacity of protein extracts. Several variables influenced the amount of oil that could be emulsified by 1 mg of soluble protein. The amount of soluble protein in the original aliquot used, the speed of mixing, the final temperature of the emulsion, and the amount of oil initially added, each influenced the emulsifying capacity of the soluble protein. The rate of addition of oil did not affect the amount of oil emulsified. Any differences in the effect of rate of addition of oil could be attributed to a temperature difference. Photomicrographs were made of emulsions showing the protein‐oil relationship at increasing amounts of oil before and after emulsion breakdown. A method for predicting the stability of emulsions was used to verify the method developed.

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SUMMARY– Surface tension responses for solutions of salt‐soluble protein from cow meat, beef hearts, beef cheek meat, pork trim and pork cheek meat were found to follow the Type III curves assigned to surface‐active agents. The stability of emulsions prepared utilizing salt‐soluble protein of the meats was significantly affected by concentration of protein and level of oil. As either concentration of protein or of oil was increased, higher and more significant stability of the emulsions was observed. Emulsions prepared from protein of each type of meat had similar responses for stability. High and significant correlation was found between protein surface activity and emulsion stability. Little change in emulsion viscosity was found except at the upper protein and oil levels tested.

An experimental technique was utilized which allows the observation and photographic recording of film formation at an oil‐water interface. Salt soluble protein of cow meat and beef hearts, sodium caseinate and gum acacia showed extensive interfacial film development. No films were observed from solutions of soy sodium proteinate or propylene glycol alginate.

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