Some time is required for the conversion of the starch by this animal diastase, and in some animals there is a special laboratory or kitchen for effecting this preliminary cookery of vegetable food. Ruminating animals have a special stomach-cavity for this purpose in which the food, after mastication, is held for some time and kept warm before passing into the cavity which secretes the gastric juice. The crop of grain-eating birds appears to perform a similar function. It is there mixed with a secretion corresponding to saliva, and is thus partially malted—in this case before mastication in the gizzard.
At a later stage of digestion, the starch that has escaped conversion by the saliva is again subjected to the action of animal diastase contained in the pancreatic juice, which is very similar to saliva.
It is a fair inference from these facts that creatures like ourselves, who are not provided with a crop or compound stomach, and manifestly secrete less saliva than horses or other grain-munching animals, require some preliminary assistance when we adopt graminivorous habits; and one part of the business of cookery is to supply such preliminary treatment to the oats, barley, wheat, maize, peas, beans, etc., which we cultivate and use for food.
XXXI.
Having described the changes effected by heat upon starch, and referred to its further conversion into dextrin and sugar, I will now take some practical examples of the cookery of starch-foods, beginning with those which are composed of pure, or nearly pure, starch.
When arrowroot is merely stirred in cold water it sinks to the bottom undissolved and unaltered. When cooked in the usual manner to form the well-known mucilaginous or jelly-like food, the change is a simple case of the swelling and breaking up of the granules described as occurring in water at the temperature of 140° Fahr. There appears to be no reason for limiting the temperature, as the same action takes place from 140° upward, to the boiling-point of water.
I may here mention a peculiarity of another form of nearly pure starch-food, viz., tapioca, which is obtained by pulping and washing out the starch-granules of the root of the manihot, then heating the washed starch in pans and stirring it while hot with iron or wooden paddles. This cooks and breaks up the granules and agglutinates the starch into nodules which, as Mr. James Collins explains ("Journal of Society of Arts," March 14, 1884), are thereby coated with dextrin, to which gummy coating some of the peculiarities of tapioca-pudding are attributable. It is a curious fact that this manihot-root, from which our harmless tapioca is obtained, is terribly poisonous. The plant is one of the large family of nauseous spurgeworts (Euphorbiaceæ). The poison resides in the milky juice surrounding the starch-granules, but, being both soluble in water and volatile, most of it is washed away in separating the starch-granules, and any that remains after washing is
