A. Prepare Sweet Pickled Peaches. Use one peach.
1/2 peck peaches 2 lbs. brown sugar
1 pint vinegar
1 oz. stick cinnamon
Scald the peaches, peel them, and stick them with three or four cloves. Cook until tender a few of them at a time, in a syrup made by boiling together the sugar, cinnamon, and vinegar. Put in jars.
B. Class Experiment.
Conditions favoring Growth of Micro-organisms.
Try the following experiments, using petri dishes, or saucers covered with tumblers or sheets of glass:
1. Place a piece of bread in each of two dishes. Leave the first piece of bread dry; moisten the second piece with water. Expose both to the air for five minutes in a room where people are moving about. Cover, and keep both in a dark place (as, for example, in a cupboard) for two days, and observe the results.
2. Place a piece of bread in another dish and moisten it. Expose it for five minutes in a room when no one but yourself is present, and do not move more than you can help during the exposure. Keep this dish also in the dark for two days and compare with the second dish in (1).
3. Put pieces of bread (moistened) in four dishes, and expose all at once for five minutes in a room with people moving about.
a. Keep the first in a warm room.
b. Keep the second in an ice-box.
c. Keep the third in the sunlight as much as possible.
d. Keep the fourth in a dark, warm place.
Examine these at the end of two days. If necessary, let them stand longer. What effect has dryness or moisture, warmth or cold, light or darkness, on the growth of mold ? Account for the difference in (2).
Food might seem to be the first condition necessary to the growth of micro-organisms, and so it is; and yet they seem able to live for a fair length of time without food. They blow around in the air, or are transmitted by water, in neither of which elements are they fed. Under these circumstances, it is true, they are not growing or multiplying, and may even be in the spore state, but once the organisms reach available food, they begin to grow and reproduce with wonderful rapidity.
Water, as well as food, is necessary, but different organisms vary somewhat in regard to the necessary amounts. Bacteria and yeasts require a goodly proportion of water, and it is only in watery foods that they are capable of much growth. Sugar and flour, for example, are much too dry for them. Twenty-five to thirty per cent of water is necessary for any growth, and, even then, it will not be vigorous. Most bacteria cannot grow in foods which are strongly acid, but molds do not mind the acid, and as only small percentages of moisture are necessary to keep them alive, in damp weather as dry a food as flour may become moldy. Even books and clothes may mold in a damp room. Mildew is one species of mold.
Bread that is in a closed bread-box is apt to become moldy if left too long; but if bread is spread out, exposed to the air, it will probably dry without any molding at all. Possibly this is because a moving current of air dries up the moisture; but, whatever the reason, it is true that mold grows best in still air.
Bacteria differ greatly in relation to air. Some grow only in the presence, others in the absence of it, and some can prosper either way. The bacteria that live without air cause putrefaction and are perhaps most likely to produce ptomains; but the majority of bacteria grow best in an abundance of air, and most foods begin to spoil on the surface.
Direct sunlight rapidly kills bacteria, and any daylight makes them grow more slowly and less vigorously. Molds may grow in either light or darkness, but they, too, grow best in a dark place. Plenty of light and fresh air, then, are the housekeeper's allies in the fight against micro-organisms.
Another method of checking the growth of micro-organisms is by means of low temperatures. Few organisms can make any but the most feeble growth in the cold. Even rather slight differences in temperature seem to have surprisingly great effects.
For this reason food is placed in an ice-box to delay the growth of the micro-organisms, but as the temperature, even in very well-constructed refrigerators with a large ice chamber, is forty to forty-five degrees, usually nearer fifty degrees Fahrenheit, growth can be delayed only for a limited time. Such food will spoil eventually. But a temperature even of sixty degrees is still a great aid in keeping food temporarily. Cold storage is more efficient than home refrigeration, because a lower temperature is used.
There are other means of preserving food, besides the use of cold temperatures. Drying evidently prevents the growth of bacteria, since they need so much water, and, if this is thorough, it may also prevent mold action. Dried fruits of all kinds have long been used, as have also some dried vegetables. Lately, more kinds of dried vegetables have been put upon the market, and even desiccated soups. All these are good food, as nutritious as before drying, but they do not retain quite the original flavors.
Foods which can be boiled and canned may be made truly sterile, and if the process is carried out properly, such materials will keep indefinitely. Fruits and vegetables may well be taken care of in this manner.
In recent years, still another method of preserving food has been used. This consists in the addition of something which will at least lessen the growth of germs, if not entirely prevent it. The difficulty is to find substances which will do this and yet have no harmful effect upon the people who eat the food. Among the substances commonly used for this purpose are borax, benzoic and salicylic acids, and formalin. These are all known to be harmful if taken in large amounts, but they are believed to have comparatively little effect in small quantities. But because, if they are allowed at all, it is difficult to be sure that they will be in sufficiently small amounts, and because repeated doses possibly may cause trouble, or small doses from a number of foods combine to make a large dose, and because some people (such as young children and invalids) are more susceptible to them than others, the national pure food law has forbidden the ordinary use of them, unless the kind and amount of any such added substance is plainly printed on the bottle or can in which the food is sold.
There are, however, some food substances which, themselves, have something of the preserving effect. Mixing foods with sufficient sugar protects them well from bacteria or mold growth, but not quite so well against yeasts. Raisins, dates, and figs all have so much sugar in them that it is not necessary to add any more to insure their keeping well, when they are partially dried. Salt, too, has preservative action, and salting fish is a usual device for keeping it. Other foods, like corned beef, are kept immersed in brine, - that is, in salt and water. Salted butter, too, keeps better than fresh, and perhaps that is why so little fresh butter is used in this country. Salty foods are undoubtedly not so digestible as fresh, and the use of such foods for invalids and young children is questionable. Vinegar, sometimes reinforced by spices, is another food preservative, but pickled foods will not keep indefinitely. Many of the common spices also have some preservative power. Mince meat, if kept cool, will remain in good condition for a long period. Fruit-cake, which is highly spiced, keeps well. Sausage is another food which is spiced in order to prevent spoiling. But pickled or spiced food, like that preserved in salt, is probably far less digestible than in the original form, and the too frequent use of it is to be avoided.
U. S. Dept. of Agriculture. Farmers' Bulletin No. 375. "Care of
Food in the Home." Farmers' Bulletin No. 459. "House Flies." Farmers' Bulletin No. 353. "The Ice-Box." Conn. "Bacteria, Yeasts, and Molds in the Home", sections on
Yeasts and Bacteria. Cornell Reading Course for the Farm Home. "Preservation of Food in the Home ", especially pages 281-286 inclusive.
1. Under what circumstances is it wise for a housewife to put up much fruit?
2. Why is drying a means of preserving fruits and vegetables?
3. What preservative is sometimes added to commercial catsup?
4. How must an ice-box be taken care of?
5. What foods should never be placed in an ice-box?
6. What kinds of foods is it unnecessary to keep in a cool place, and why?
7. Why should butter and milk be covered when in the refrigerator, and if possible kept in a compartment by themselves?
8. When a bread-box smells musty how must it be cared for?