Experimental cookery

Tests for quality. A candler's grading of the egg is based largely on the size of the air cell and the visibility of the yolk. Perry found that yolk color, ascertained after breaking the egg, influences the yolk shadow and the 3'olk movement, as determined in candling. The dark yolks cause a darker shadow and increase the apparent movement, though the percentage of thick albumen did not influence the yolk shadow and movement. The air cell increases in size with loss of water from the egg. The less the humidity of the air in which the egg is stored, the greater the loss of water. When water is lost to the outside air the total solids of the egg increase. The changes in the cooking quality of the white and yolk may not be so detrimental as when the w\ater loss is prevented. Since the size of the air cell increases with the loss of water, the humidity of storage rooms is usually controlled to prevent a large moisture loss. But other changes, more detrimental to the quality of the egg than water loss, may occur. Almquist, Givens, and Klose say that the transmission of light varies for different layers of egg albumen, being lowest for the firmest or gelat- inous layers. They find the transmission of light to be correlated with the percentage of mucin in the albumen. In addition it varies with the tem- perature and pH, both of which affect the physical condition of the mucin. FACTORS AFFECTING QUALITY OF EGGS 327 At lower temperatures and at lower pH the translucency of the mucin fibers is lessened. Wilcke used a torsion pendulum to measure externally the interior viscosity of an egg and from observations worked out an index K, which was a measure of the combined viscosity of the entire contents of the egg. He found that the K value increased with increased weight of the eggs, but that the rations used did not affect the K values of the eggs produced by hens on the rations used in his study. The index, K, is a characteristic of the individual hen. Standing-up quality of the yolk. Sharp has worked out a system of determining the quality of the egg from the standing-up ability of the yolk. If a fresh egg of good quality is broken out of the shell, the yolk stands up. But as the interior quality deteriorates the yolk flattens out more and more readily until a stage is reached at which the yolk membrane breaks, no matter how carefully handled, when the shell is broken. Both the time the yolk is on the dish and its temperature affect the extent of flattening, the flattening being greater with longer time and a higher temperature. By dividing the height of the yolk by its width a numerical index is obtained that indicates the quality of the egg. The measurements of the yolk, after being freed of the white, taken 5 minutes after it is laid on the Petri dish and at a temperature of 25°C., give an average value of about 0.41 for eggs 3 to 4 hours old. With deterioration of the egg the index becomes less, and breaking occurs when the index falls to about 0.25. The standing-up ability of the white may also be used to determine egg quality.