Coagulation of Proteins

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4A.2
RRL
4A.2.1 Coagulation of Proteins
Coagulation of protein refers to sticking together, like a blood clot, usually as a result of denaturation or coming out of solution due to abnormal ionic strength or a change of solvent. Definite characteristics of the proteins are changed when they are coagulated, among which is loss of solubility in water and dilute salt solutions. In some instances and under certain conditions the coagulation process may be reversible. (Campbell, et.al, 1979) 4A.2.2 Chemistry behind Coagulation

Ovalbumin the main protein in egg white is a globular protein denatured by heat, this means reaction is more rapid with an increase in temperature of heating. Since heat is absorbed during coagulation of egg proteins, the reaction is endothermic. Egg white coagulated by heat changes from a transparent viscous solution to a opaque white gel, the water of white trapped by the protein. (De Mann, 1986) 4A.2.3 Chemistry behind Opalescence

Opalescence is a type of dichroism seen in highly dispersed systems with little opacity. The material appears yellowish-red in transmitted light and blue in the scattered light perpendicular to the transmitted light. The phenomenon is named after the appearance of opals (Fennema, 1996). There are different degrees of opalescent behavior. One can still see through a slightly opalescent phase. The more particles and the bigger the particles are, the stronger the scattering arising from them and the cloudier the particular phase will look. At a certain concentration the scattering is so strong that all light passing through is scattered, so that it is not transparent any more (Fennema, 1996).

4A.2.4 Different Factors that Influence Coagulation of Proteins

Coagulation is influenced by factors such as heat, beating, pH and also use of sugar and salt. Heat should be slow and mild. The egg white coagulates, and become solid at temperatures 62-65C. Egg yolks begin to coagulate at 65C and become solid at 70C....
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