Gelation Properties of Albumen Proteins, Singly and in Combination

Studies of gelation properties of the albumen proteins in a custard model system showed that conalbumin was the least heat stable protein with a denaturation temperature of 57.3 C. Globulins and ovalbumin ranked second with denaturation transition temperatures of 72.0 and 71.5 C, respectively. Lysozyme denatured at 81.5 C while ovomucin and ovomucoid showed no coagulation abilities. Lysozyme produced the strongest gel followed by globulins, ovalbumin, and conalbumin. In a study of binary mixtures, aggregation of polypeptides occurred near the denaturation transition temperature of the least heat stable protein. Therefore, in combinations of lysozyme, globulins, and ovalbumin with conalbumin, denaturation was apparent at 58.3, 57.8, and 58.1 C, respectively. Ovomucoid consistently increased the coagulation temperature ranges of globulins, conalbumin, and ovalbumin, and prevented coagulation of lysozyme. Gel strength varied according to the proteins present. The combinations of five or all proteins resulted in more subtle changes of temperature during coagulation. The destabilizing effects of conalbumin on the other proteins were still apparent. The control mixtur e exhibited two distinct coagulation temperature ranges of 61.5 to 62.5 C and 73.0 to 71.0 C. In the scanning electron microscopic investigations of selected coagulums it was found that lysozyme, conalbumin, and ovalbumin polypeptides aggregated in grape-like clusters of variable size. The control mixture gel also exhibited the same pattern. Globulins polypeptides appeared to tighly associate in membrane-like arrangements and showed excellent binding abilities. Small cluster sizes seemed to parallel gel firmness.