Factors affecting coagulation of egg proteins

FOOD SCIENCE AND PROCESSING 3 (2+1)
Lesson 19 :Eggs - Processing, Preparation and Preservation

Factors affecting coagulation of egg proteins

  1. Concentration: The temperature at which egg proteins coagulate and the time required for coagulation depends in part on the proportion of egg in any mixture. Dilution of egg increases the temperature at which coagulation occurs.

  2. Part of egg used: Egg yolk proteins require a slightly higher temperature for coagulation than egg white.

  3. Intact or stirred: The texture of coagulated egg yolk, when it is cooked intact, is crumbly and mealy but solid. When the yolk membrane is ruptured and the stirred yolk is heated, however, the texture of the resulting gel is firm and rubbery. The difference in texture of intact and stirred egg yolk may result from changes that occur in the intricate microstructure of egg yolk with stirring. The tiny discrete granules of the intact yolk may form a highly cross-linked protein network when it is disrupted.

  4. Time and temperature: The rate of coagulation and the amount of coagulum formed in a definite time increase with increasing temperature. The character of the coagulum formed when egg white is heated at high temperature is firm, as compared with the soft, tender, more evenly coagulated product obtained when coagulation takes place at lower temperature.

    The toughness and greater shrinkage of the protein coagulated at a high temperature are the basis for the recommended use of low or moderate temperatures for egg cookery. If eggs are cooked in water, temperature should be 85oC that will produce a texture that is tender yet firm.

    Oven temperatures from 148.8 to 176oC have been found to be satisfactory for cooking eggs and egg dishes. Plain egg dishes in a pan of water when baking them in the oven helps to protect the egg product from becoming over-cooked.

  5. Micro organisms: Salmonella enteritidis may infect the reproductive system of some laying hens, which may lay eggs contaminated with the organism. A possible danger may arise, therefore, from eating raw or lightly cooked eggs. Hence such egg preparation should not be served for infants and pregnant mother. At warm temperatures, micro-organisms can increase rapidly which is why eggs should always be properly refrigerated.
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Last modified: Monday, 12 December 2011, 6:47 AM