A. Various Methods of Boiling Potatoes.
(Each student is to try one way and compare the result with the others.)
1. Wash and scrub a potato. Cook it in boiling salted water until it is soft. Allow one teaspoon of salt to one quart of water.
2. Boil a potato as directed in (1), but pare it before boiling.
3. Boil a potato as in (1), but, before boiling, cut off a strip of the skin all around the potato.
How do these potatoes differ in color and in mealiness, after they are done ?
Mash the potato with a fork. Beat till light and creamy. Add two teaspoons of hot milk, one-half teaspoon of butter, and season with salt, while beating. Heap the potato on a buttered plate and make an indentation in the middle of the heap. Open an egg, being careful not to break the yolk, slip it into the indentation in the potato, and place all in an oven until the egg is cooked sufficiently to suit taste. Season egg with a very little butter, salt, and pepper. Pimento may be rubbed through a strainer and beaten into the potato at the beginning to add color and flavor.
1. Pare a small potato; cut off a slice and leave it exposed to the air for half an hour.
2. Grate the rest of the potato into a piece of cheese-cloth. Gather up the corners of the cloth and, by squeezing, press out all the liquid possible. Then wash in a bowl of water till nothing more can be extracted. Allow the water to stand, and examine the sediment. Look at it under the microscope. Boil a portion of it. Test a portion with iodine. A blue color indicates the presence of starch.
3. Examine the contents of the cheesecloth. What ingredients of potato have you found so far?
4. Put a pared potato into a large kettle of cold water, and then put the kettle on to boil. When the potato is cooked, compare it with those started in boiling water in (A).
C. Class Experiment.
Different Stages in the Boiling of Water.
Heat some water in a saucepan to boiling; meanwhile, with a thermometer, take the temperature of the water at the following stages:
1. When the first small bubbles appear on the bottom and sides of the pan. (What are these bubbles ?)
2. When the water feels neither hot nor cold to the hand. (Lukewarm)
3. When somewhat larger bubbles appear around the edge and at the bottom of the pan. (Scalding) What are these bubbles ?
4. When the bubbles begin to rise. (Simmering)
5. When the bubbles rise rapidly, breaking, and completely agitating the surface of the water. (Boiling)
6. Increase the heat and see if the water gets hotter.
The name potato is a corruption of the last part of the Latin name for sweet potatoes, ipomoea batata, but the name by common consent is given to our white potato. White potatoes are a native of America, perhaps of Chile, and were not known in Europe until about 1580. They were introduced into North America about the same time. At first, they did not meet with great favor in Europe, and it was not until there was shortage in a series of staple crops that they sprang into favor. Now they have been adopted in Ireland to such an extent that they form a large part of the food of the people, and for that reason are often called Irish potatoes.
Potatoes form forty per cent of the total vegetable crop of the world, so that their name of king of vegetables is not undeserved, and they are next in importance among the vegetable products to cereals. When we compare these facts with the report that at the time of our American Revolution a well-to-do family thought itself fortunate if it had at most a barrel of potatoes for its winter supply, and that these were only served on special occasions and for honored guests, we can see how greatly the relative importance of the position of the potato has changed.
The potato is a tuber, that is, an underground stem which is thickened and has become a storehouse for future plants. The eyes of the potato are buds from which the new plants will sprout under proper conditions. These new plants use the food material which is stored in the potato, and the tuber itself is thereby gradually rendered unfit for food.
Composition of the Potato.
The average loss of nutrients from boiling is shown by the shading.
If a thin slice across a potato is held up to the light, four distinct parts are observable. First comes the grayish brown skin, which corresponds with the bark of an ordinary stem. Underneath this is the cortical layer, which may be from a tenth to a fifth of an inch thick, and is often slightly colored. If this layer is exposed to sunlight for some time, it will turn green, showing its relation to the green layer which is found underneath the bark of an ordinary stem. The inner layers are known as the flesh of the potato, and, for our purpose, may be considered as one. The potato is made up of a network of cells: the cell walls being, of course, largely cellulose. The cells are filled with water in which is dissolved mineral matter, a little sugar, and most of the protein* which is found in the potato. In the cells and surrounded by this water are the starch grains. While a little fat is also present the amount is so small that it need not be taken into consideration.
Sections of the Potato.
a, skin; b, cortical layer; c, outer medullary layer; d, inner medullary layer.
* Protein is the foodstuff containing nitrogen, and is essential for building body tissue which contains nitrogen.
The potato is largely composed of water, seventy-eight and three-tenths per cent, so over three-quarters of the whole weight is water. Of the eighteen and four-tenths per cent carbohydrate, about sixteen per cent is starch. There is only four-tenths of one per cent of cellulose present. Although they are small in amount, the two and two-tenths per cent of nitrogenous matter and one per cent of mineral matter are important.