Experimental cookery

Certain water, such as hard water, softened water, or water from many streams, is alkaline in reaction. Rain water, snow, or ice water is usually about neutral. If the cooking water contains alkaline salts, these salts may neutralize the non-volatile acids, and if there is a slight excess of alkaline salts the green color is intensified. To a certain extent the intensification depends upon the quantity of water used, for the larger quantity of water contains a greater quantity of alkaline salts. If the water is only slightly alkaline the plant acids may not all be neutralized and the olive-green color may develop. If the water is very alkaline and considerable water is used, not enough volatile and non-volatile acids will be liberated to neutralize the alkalinity of the water, the cover can be kept on during cooking, and the product will be bright green. With longer cooking the heat may have more effect upon the chlorophyll than the alkaline salts of the water. The addition of sodium bicarbonate (baking soda). Experiment 17A, 5, also intensifies the green color. Canned spinach, asparagus, peas, and string beans have a deep olive-green color due to the retention of the plant acids during processing and to the high temperature at which they are processed. Green vegetables like cabbage, Brussels sprouts, and spinach cooked in milk may remain a bright green color. Owing to the ease with which milk scorches and boils over there is usually less tendency to cook the vege- tables too long when milk is used. Heat decomposes chlorophyll, an olive-green color being produced. The extent of decomposition depends upon the time of heating and the tem- perature reached. With a very short cooking period little destruction may occur, but with a longer time all the chlorophyll may be decomposed. At lower temperatures the change is less rapid and at higher temperatures more rapid. Thus in a pressure cooker the change is rapid, since the tempera- ture is high and acidity is not decreased because the volatile acids are retained. Increasing the alkalinity by using alkaline water or adding soda 114 FRUITS AND VEGETABLES retards the color change by heat. However, the addition of soda is not advisable, because it softens the cellulose rapidly so that the vegetable with slight over-cooking becomes mushy or even slimy and the destruction of some of the vitamins is hastened. The cooking of green vegetables that contain enough acid to taste sour, like sorrel, sour grass, and dock, always produces this olive-green color no matter how cooked or for how short a time. Their acid content is too high to be neutralized by the alkaline salts of water or the addition of baking soda in small amounts. Green fruits like gooseberries, green grapes, and green plums develop an olive-green color when cooked. If the fruits are mature they may also contain yellow pigments that modify the color to a certain extent. If acid is to be added as a seasoning to green vegetables it is preferable to add it when served, for there will not be so long a time for the acid to react on the chlorophyll and less brown color will develop. When vegetables are cooked with added acid, the softening of the vegetable is prevented to a slight extent.