A. Prepare Apple Tapioca.
11/2 tbsp. Minute tapioca
1/3 c. water
A pinch of salt
Cook together in a double boiler until transparent (about fifteen minutes). Pare and core a sour apple. Put in a buttered baking dish, and fill the cavity in the apple with sugar. Pour the tapioca over it, and bake in a moderate oven until the apple is soft. Serve with sugar and cream.
Wash the rice thoroughly in a strainer in a bowl of water, rubbing the rice between the hands. Change the water, until it remains clear. Cook by the following methods:
1. Gradually sprinkle two tablespoons of rice into two cups of rapidly boiling water with one-half teaspoon of salt added.
2. Cook two tablespoons of rice in two-thirds of a cup of boiling, salted water for five minutes. Finish cooking in a double boiler. (Why is less water used ?)
3. Cook two tablespoons of rice in two-thirds of a cup of boiling, salted water for five minutes. Then place in a mold and steam.
In all cases cook until the rice is soft. a. Compare the time used to cook by the different methods.
b. Compare the appearance of the kernels as a result of the different treatments.
c. Note also the relative amounts of rice before and after cooking.
Starch occurs in the cells of all plants as tiny white granules, but the size, shape, and appearance of these differ with the kind of plant from which they are taken. A plant manufactures sugar from the carbon dioxide in the air and from water, and this sugar is used as nutriment for the plant, being dissolved in the juice or sap and circulating through it. But since the plant has to store some of this nutriment for future use, it manufactures starch from some of the sugar. Starch has the advantage over sugar that it is not soluble in water. The material is carried into the cell as a solution of sugar which can pass readily through the cell wall and is then turned into granules of starch. When the starch is finally used as the plant food, this process is reversed, the granules change into sugar again, and can then pass out through the cell wall.
Scientists do not agree entirely in regard to the construction of starch granules, but they believe that they are made up of at least two kinds of starch which are sometimes named red and blue amylose. Amylose is merely the scientific name for starch, and the names red and blue are given to the two kinds not at all because of their color, for they are both white, but because of the colors which they turn with iodine. The starch inside the granules and composing the greater part of the grains is blue amylose, easily digested. Its outer covering is red amylose, much more difficult of digestion and impervious to cold liquids. If the starch grain is heated in water, it begins to swell, till its outer covering is stretched thin and allows liquids to pass readily through it. In this form digestive juices can get at the starch inside to digest it; and, therefore, cooked starch is more digestible than raw.
Starch granules found in potato and arrowroot seem to be made up of only these two kinds of starch, but those in cereals seem to contain a small amount of a third kind called rose amylose. This is more difficult of digestion than is either of the other kinds, but with long boiling can be made to change into blue amylose. As it seems to be rather hard to cook the starch granules when they are shut up in the cell walls of the seed, this may be the reason why cereals take such a long time to cook. Corn starch is, of course, a cereal starch, and ordinary wheat flour, too, contains an abundance of starch; but in grinding the grains, the cell walls are broken and so there is not the
Starch Grains, Magnified Many Times a, cells and starch grains in a raw potato; 6, in a partially cooked potato; c, in a thoroughly boiled potato.
From Leach'a "Food Inspection and Analysis." same difficulty in getting at the starch for cooking. If, during the cooking of starch, as, for example, in the cooking of oatmeal, the surface is left exposed so that the top dries, the starch is changed into a hard skin which is exceedingly difficult of digestion. If the oatmeal is stirred occasionally and kept covered so that the steam is confined in the space above the surface, no such change occurs.
When a vegetable food containing much starch, such as potatoes or cereals, is cooked, the starch granules swell in the process until they burst most of the cell walls of the plant.
Changes of Starch Grains in Cooking.
Starch is not soluble in cold water, but, when heated, the granules finally break down and gelatinize. This is only partial solution. When a substance really dissolves, it disappears entirely from view, as sugar does in water. It may impart a color to the solution, but it does not render it opaque. Because starch does not dissolve, it cannot pass through the lining wall of the intestines and so must be changed in digestion before it can be absorbed. A ferment called ptyalin is found in the saliva, which is capable of acting on starch and changing it to sugar. There is an intermediate stage in this action, for the starch is first changed into dextrine. Dextrine is whitish like starch, but with iodine turns a beautiful wine red. Unlike starch, it is soluble in cold water. When starchy food is chewed saliva is mixed with it, and as the food lies in the fundus (or middle part) of the stomach the ptyalin has a chance to act on it. It used to be thought that this action stopped as soon as the food reached the stomach, for ptyalin cannot act in gastric juice, but it is now known that this change can go on for about two hours before the gastric juice is so mixed with the food that the action is stopped. Therefore it seems a somewhat important matter that such food should be chewed thoroughly and mixed with saliva and not swallowed whole or washed down with liquids. In the stomach, however, not all of the starch is digested. Probably most of it does not go beyond the dextrine stage.
In the intestines there is another ferment, sometimes called amylopsin, which, like the ptyalin, can digest starch. We are, then, apparently, well equipped to digest starch, and this is fortunate, for starch forms a large proportion of the nutrients of our diet.
Dextrine may also be formed by heating dry starch very hot, at least to 320° F. It is formed somewhat in toast, and in the crust of bread, and in browned flour, since in these cases the starch is exposed to intense heat. Some breakfast foods are partially dextrinized and this is supposed to make them more digestible. In reality, so small a percentage of the starch is changed that they are really not very different.
Browned flour does not possess the thickening power of ordinary flour because the dextrine in it dissolves instead of gelatinizing. Since heating with acids will dextrinize starch at a much lower temperature, and only a few drops of acid are necessary to bring this about, it is sometimes
Starch Grains, Magnified Many Times
From Leach's "Food Inspection and Analysis." possible to obtain this result when it is unexpected and undesired. When a lemon filling for a pie or a boiled dressing that is made with flour are cooked too long or with too much acid, they may grow thinner instead of thicker as the cooking continues. So, also, if creamed oysters are kept hot too long a thick white sauce may become very thin.
U. S. Dept. of Agriculture. Exp. Station Bulletin No. 202. "The Digestibility of Different Kinds of Starches ... as Affected by Cooking."
1. Where does a plant obtain the necessary elements to make starch? How does it take in water? How does it get carbon?
2. What purpose has the plant in manufacturing starch, and in what parts of plants would you expect to find the largest stores of it?
3. How is rice grown, and where do we obtain our largest supply?
4. What is the composition of rice? Why is it not used as an exclusive diet?
5. What is the difference in price of different grades of rice, and to what is this due?
7. Why not bake rice as we do potatoes?