A. Repeated Extractions of Juice for Jelly-Making.
Use sour apples or quinces.
1. Cut fruit in small pieces, without peeling or removing seeds. Place one cup of fruit in a kettle, cover with water, and cook until the fruit can be mashed easily. Strain juice through a jelly bag, allowing it to drip through without squeezing the bag. Reserve the pulp for a second extraction. Test one teaspoon of the juice for pectin. Keep the juice for jelly-making, marking it "Extraction 1."
2. Add water to the pulp reserved in (1) and proceed as before. Test one teaspoon of the juice for pectin. Reserve the rest of the juice, Extraction II, for jelly-making.
3. Make a third extraction. Again test one teaspoon for pectin. Reserve this third extraction for jelly-making.
B. Jelly from These Extractions.
1. Make jelly from Extraction I, using: a. Three-fourths as much sugar as juice.
b. Equal parts of sugar and juice.
2. Boil Extractions II and III together rapidly, until the resulting juice approximates the richness of Extraction I. (This may be tested by alcohol, by the color and taste.) Measure. Make jelly, using proportion of sugar to juice that is found to give the best results.
C. Class Experiments. Food Preservatives. Sterilize small bottles or test tubes.
1. Place a piece of uncooked fruit in each.
a. Cover fruit with brine.
b. Cover fruit with a fifty per cent solution of sugar.
c. Cover fruit with a ten per cent solution of sugar.
d. Cover fruit with water and add ground cinnamon, clove, or mustard.
e. Cover fruit with water and add allspice or nutmeg.
/. Cover fruit with vinegar.
g. Cover fruit with oil.
h. Cover fruit with alcohol.
2. Allow the tubes to stand for several days and examine from time to time until it is determined which substances act as preservatives.
D. Class Work. Prepare Cucumber Pickles.
Make unripe cucumber pickles, using one-fourth of a cup of cucumbers.
Wipe about a dozen small, unripe cucumbers and cover them with brine made by dissolving one tablespoon of salt to a cup of boiling water. After three days, drain off the brine, reheat it to boiling, and again pour it over the pickles. After a second three days, drain the cucumbers, cover them with boiling water in which a salt spoon of alum has been dissolved for every cup of water used. Allow them to stand for six hours, then remove them from the alum water, and cook for ten minutes in a part of the following mixture heated to boiling:
1 pint vinegar 1/2 red pepper
1/4 tbsp. allspice berries 1/4 tbsp. whole cloves
Pack the cooked pickles in a jar and strain the rest of the mixture over them.
As has already been said, yeasts as well as molds belong to the colorless plants and fungi. The yeast which is used in making bread is a collection of thousands of tiny yeast plants, each of which is too small to be seen without the aid of a microscope. These plants are even less like ordinary plants than are the molds; they consist merely of a single cell which appears, under the microscope, as a colorless oval. These yeast plants are so small and light that, like the spores of the molds, they float about in the air.
Fruits preserved in sugar are especially apt to undergo a change which, as can be seen at once, is not due to mold growth. This is the action that takes place when preserves "work " or ferment, and it may occur also in jellies or syrups. Anything which contains sugar and water may show this change. The change is characterized by a sharp, pungent taste, and at some stages by the formation of bubbles through the liquid. Whenever these phenomena occur, it is a sign that growing yeasts are present. For yeasts, when they grow, are able to break up the sugar which is present and change it partly into alcohol, which gives the stinging taste, and partly into a gas called carbon dioxide, the escape of which through the liquid makes the bubbles.
While yeasts are producing these results, they are multiplying rapidly by a method called budding. In this way new cells are formed which appear first as very tiny buds on the sides of the first cells and gradually grow larger and larger until finally they separate into independent cells. When active fermentation is going on, the yeast present is always found to be in this growing state. If, however, conditions are unfavorable, some yeast plants can form within each cell a number of spores, each of which is capable of developing again into a new plant. This spore formation usually happens if there is sufficient moisture present, but not enough food to produce growth. The air may be laden with these spores and even with some of the yeast cells themselves, as well as with the spores of molds.
Other micro-organisms carried by the air are called bacteria. They are as simple in structure as the yeasts, and like them consist of single cells. They may, however, have three distinct shapes. Some are like little rods and are called bacilli (a bacillus, for a single one), others are like spheres and are called cocci, the third variety is spiral and is named spirilla (in the singular, spirillum). But all these, no matter what shape they may be, reproduce in the same way, and it is this method of reproduction which distinguishes them from the yeasts. Each cell grows a little longer than it was before and then breaks in two, each half being an individual. This process, known as reproduction by fission, gives to bacteria the name of fission fungi.
Like yeasts, some bacteria can produce spores under unfavorable conditions. A bacterium, however, instead of producing a number of spores, forms only a single one. The advantage of the spore state seems to be in the greater power of resistance that the spore possesses - it is less easily killed by heat or cold or drying. If food is being sterilized and spore-forming bacteria are present, it is quite possible that the heating will kill all of the bacteria but the spores will be left alive. By the following day, however, the majority of these spores will have again changed themselves into the ordinary forms of bacteria, and a second heating will kill these forms. A third heating is safest to make sure that any spores remaining the second day are destroyed. Both yeasts and bacteria are too small to be seen without a microscope; but of the two, yeasts are much the larger. While a yeast cell is about one three-thousandth of an inch in diameter, even the largest bacterium has a diameter of not more than one ten-thousandth of an inch. It might well seem as if organisms as small as this could not do us either much harm or much good, and this would probably be true if it were not for the wonderful rate at which they can multiply. In a bacterium, division may take place every half hour, and at that rate, in only one day, conditions being favorable, a single cell could produce about seventeen million others. If, then, food is to be kept from spoiling, it is obviously necessary to exclude the entrance of even one bacterium.
When bacteria first act upon food, the result may be only beneficial; the good flavor of butter and some cheeses is undoubtedly due to their action. Bacteria, however, will finally render food unfit for use, producing decay and putrefaction. But what a world it would be if micro-organisms did not bring about these processes. Our world would be littered with useless material, and the soil long ago would have become exhausted.
Bacteria may be divided into three distinct classes: first, those capable of producing diseases, such as typhoid and diphtheria; second, those which in the process of growth produce substances poisonous to us. These sub-stances, called ptomains, are the cause of the ptomain poisoning cases which occur from time to time. The third class is composed of those that are either harmless or beneficial to us. The bacteria which cause milk to sour not only are not any more poisonous to us than are any of the other vegetable plants used for food, but they may be of positive benefit in keeping down the growth of more harmful organisms.
"Swat the fly" has become a slogan in modern times. A glance at the enlarged diagram of a fly, particularly of the feet, will show why it is considered objectionable to have flies around, and especially so to have them crawl over food. Coming from infected material and filth, they may bring with them all kinds of germs. If the germs are introduced into food material, where every condition is right for their reproduction, it is evident how trouble may occur. It is very necessary then, that flies be excluded from houses as far as possible. Any flies that find entrance must be killed or caught, and care must be taken not to allow heaps of manure or garbage, or other fly-breeding material, to stand long enough for their larvae to develop and escape. Much the easiest method of keeping free from flies is to control possible breeding places. A new kind of garbage can acts as fly-catcher and, placed just outside the house, may catch many flies which would otherwise find their way in. Then garbage and flies together must be disposed of. Other insects may, of course, also act as carriers of germs, but the fly especially brings them.
Conn. "Bacteria, Yeasts, and Molds in the Home", sections on Bacteria and Yeasts.
1. Give instances in which bacteria are beneficial.
2. Why may there be more spores on the fruits and vegetables growing in a very dry season ? Why would such fruits be harder to can successfully?
3. Why, in making cucumber pickles, is the brine reheated at intervals ?
4. How should garbage cans be cared for ?
5. What are the best means of disposing of garbage ?
6. Why should all foods and dishes be covered carefully when sweeping or dusting is going on ?