Production factors including chopping temperature, chopping duration, protein-type, and order of ingredient addition necessary to produce a stable soy protein isolate stabilized fat mixture were examined. To produce a stable mixture, several steps were required. First, one part of soy protein isolate was added to four and one-half parts of 90(DEGREES)C water in a steam heated laboratory bowl chopper. After the protein and water mixture had been chopped for 60 seconds, four parts of coarse ground fat were added and chopped for a total of ten minutes at a minimum temperature of 48.9(DEGREES)C. Thirty seconds prior to the end of the ten minute chopping cycle, a solution of sodium nitrite and water was added to deter fat rancidity. Essentially no fat or water cookout resulted when a stability test of the final mixture was performed. A comparison of the physical characteristics of both the caseinate and soy isolate stabilized fat mixtures was used to speculate concerning the stabilizing structure of the fat mixtures;When added as the fat source to either a fine-textured bologna or a course-ground cotto salami, the stabilized fat mixtures were detrimental to the textural and sensory properties of the sausages. While an improvement in the stability of the fat and water in the raw meat batters was noted when soy stabilized fat mixture was used, no improvement in smokehouse yield was apparent;The functionality of several soy isolates and two caseinates was examined using the "model system" emulsion capacity test. Emulsion capacity did not adequately estimate the effect of several factors, including protein-type, heat, and addition order, on the functionality of the proteins studied. Light micrographs taken at various stages of the emulsion capacity measurement suggested that emulsion capacity is better described as a measurement of protein elasticity and self-interaction than as a measurement of the protein to lipid interaction of emulsification.