Experimental cookery

Replacing magnesium in chlorophyll products. It is very difficult to re- place the magnesium of the magnesium-free chlorophyll products. It can be done chemically by using a very reactive substance, magnesium methyl iodide, but this is impracticable to use in cooking processes. However, Will- statter states that the acetate salts of some metals such as copper, iron, and zinc will combine with phaeophytin and give very bright green-colored products. This is such a good test for small quantities of these metals that it is necessary in isolating chlorophyll to be extremely careful that it does not come in contact with them. If to the green vegetable to which acid has been added and in which the olive-green color has developed. Experiment 17A, 6, copper acetate is added, a vivid green color will develop on standing. Carotinoids. Carotinoids is a term applied to the pigments giving yel- low and orange coloring to fruits and flowers, carotene, C4oHr,o, and xanthophyll, C4oHr,(;02. The carotinoids are not soluble in water, and the pigments are not affected, to any great extent, by the concentration of acids or alkalies used in food preparation. The darkening produced by the action of alkalies by caramelization of the sugar in vegetables, like carrots, must not be confused with a change in pigment color. Carotene is easily oxidized when exposed to air. Xanthophyll can also be oxidized in the same way. One of the characteristics of the carotinoids is the intensity of their coloring. The red pigment found in tomatoes is lycopin, an isomer of carotene. Flavones and Flavonols. Flavones and flavonols are amphoteric pig- ments found in vegetables and petals of flowers. They are also found in the cell sap of the epidermis and underlying tissue of plants. Onslow gives the following formulas : FLAVONES AND FLAVONOLS 115 flavonol As they occur in nature they often have other or additional hydrogen atoms replaced by hydroxyl groups. The position of the hydroxyl groups markedly influences the intensity of color, the color usually being deeper if two hydroxyl groups are in the ortho position to each other. The flavone and flavonol pigments are yellovr in color. In plants they often occur as glucosides, one or more of the hydroxyl groups being combined with the sugar, and then the color is less intense. They give an intense yellow color with alkalies. Sometimes the quantity of them found in white vegetables is so minute that they are not visible. Adding an alkali or holding them over ammonia vapor intensifies the color and they become visible. The color changes of the flavones cannot be observed so readily in the yellow, red, or green vegetables. Rice cooked in alkaline water usually has a yellow tinge, and sometimes it is rather deep in hue or has a green tint. Rice from the same source as that cooked in alkaline water, but cooked in distilled water, has a snowy white appearance. The cooking of cauliflower, white cabbage, and particularly white onions in alkaline water often causes the yellow color to develop. Some white onions cooked in the hard water at Ames have developed nearly a sulfur yellow in color, whereas portions of the same onions cooked in distilled water remained white, or retained their natural yellow tinge.