Egg white gels were formed by heating liquid egg white at various pH, protein, and NaCl levels at different temperatures and times of heating. Hardness, cohesiveness, and springiness of gels were measured. Serum was expressed from gels and evaluated by polyacrylamide gel electrophoresis. Selected samples were prepared for scanning electron microscopy. Gel hardness rose with increasing temperature, time, pH, and protein level, and decreased with added salt. Cohesiveness and springiness increased with time and temperature of heating. Expressed serum decreased as pH, time, temperature, and protein level were increased. Gels at pH 5 and 6 had a coarse, aggregated structure. At pH 9 protein strands and globules were arranged in a uniform matrix. Salt prompted aggregation of gels.

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Hardness, cohesiveness, and springiness of heated intact egg yolks were determined by an Ins&on compression test. Hardness increased as temperature was increased from 75" to 90°C and as time of heating was increased from 10 to 30 min. Cohesiveness and springiness increased as temperature was increased from 75" to 80°C and as time was increased from 10 to 30 min. Egg yolks from cooked shell eggs were lower in all textural parameters than gels formed from stirred egg yolk. Low scores for cohesiveness and springiness were indicative of the crumbliness of yolk from cooked shell eggs; crumbliness was attributed to structural characteristics. The microstructure consisted of adjoining polyhedral grains, which showed no evidence of crosslinking. Grains appeared to be equivalent to yolk spheres, ranging in size from 40 to 100 pm. The structure of a stirred yolk gel consisted of a highly crosslinked protein matrix containing spheres (S-35 ym) and granules (l-2 pm).