Experimental cookery

In cooking eggs or foods containing large proportions of egg, the amount of coagulum formed at a definite temperature depends upon the length of time the food is held at the specified temperature and the number of degrees the specified tempera- ture is above the point at which coagulation may begin. Using filtered egg white, Lepeschkin found that, with water at a definite temperature, a longer time was required before the egg appeared turbid at lower tempera- tures than at higher temperatures. His findings may be summarized : 334 EGG COOKERY °c. Seconds req uired for coagulation 57.04 22,600 58.01 9,520 59.03 1,535 60.03 595 61.02 230 62.01 97 63.01 40 As the temperature of milk custards is elevated the firmness of the custard is increased. At a definite temperature, depending on the rate of heating, an optimum consistency is obtained. Heating to a temperature higher than this increases syneresis and porosity of the custard. Woodruff and Meyer found that by increasing the temperature from 79° to 91° by 4° intervals the strength, when tested by a gel tester of distilled-water-egg custard gels with 0.2 M and 0.05 M sodium chloride and 0.2 M magnesium chloride plus 23 per cent sugar, was increased. But at the higher temperatures the gels were porous and undesirable. The con- centration of egg used was approximately 2 to a cup of liquid. Co?icentration. Robertson states, "The concentration of the protein, and especially the presence of other substances in the solution, very markedly affects the coagulation temperature." This is illustrated in egg cookery. The whole egg coagulates at a temperature not far from 70 °C. When 1 to 2 tablespoons of milk or water are added, as in the making of plain omelets, coagulation occurs at a temperature above 70°C. When 1 egg is added to a cup of milk the coagulation temperature is much higher than that of egg alone. It is about 80°C., the amount coagulated at a definite temperature depending upon the rate of heating. If 2 eggs are added to a cup of milk the concentration of egg is greater than when 1 is used, and coagulation under the same conditions for heating occurs at a slightly lower temperature. Salts. The salt content of the egg or of the material with which the egg is combined affects the coagulation of the egg proteins. Lepeschkin has shown that, if egg albumin is dialyzed so that the mineral content is low- ered, the albumin does not coagulate on heating. He has also shown that coagulation varies with the salt concentration, that some concentrations cause coagulation and others do not. However, if, to the heated egg al- bumin that has been dialyzed, salts are added, coagulation takes place, but this often requires a definite concentration for maximum coagulation, higher or lower concentrations not being so effective or failing to bring about coagulation. The effect of the salt content on coagulation can be shown by com- bining egg as for custard, but substituting distilled water for the milk, which when heated to 83° to 86°C. does not gel. If to this distilled-water custard a definite concentration of a salt is added, coagulation will occur on heating. Salts which will bring about coagulation are iron lactate, ferric I pH AND COAGULATION OF CUSTARD 335