The United States is fortunate in the native fruit supply, including as it does so many degrees of latitude and longitude with the differences in altitude, climate, and soil needed by different varieties. Now that we count Porto Rico among our possessions, a list of our fruits would include most of the varieties known in the temperate and semi-tropical zones. The United States Department of Agriculture experiments with new varieties from foreign lands that may make themselves at home in our soil, and work like that of Luther Burbank produces new species. Scientific methods of fruit growing are becoming more common, and the quality of fruit will doubtless improve in spite of fungous diseases and injurious insects. Our wild fruits are not yet entirely rooted out. The Maine blueberry, for example, is found on hundreds of acres and needs no cultivation beyond burning over every third year.

Fruit is necessary in our diet, and is not an extravagance unless we buy fancy varieties brought from a distance, or native fruits out of season.

Composition and nutritive value.—The chief foodstuffs in fruits are carbohydrates and mineral matter. Fresh fruit contains from 75 to 95 per cent of water, and its presence is apparent in such juicy fruits as the melon and the orange. Figure 25 shows that seemingly dry fruits like the banana and the apple also contain much water. Even fruits which have been artificially dried, like prunes and raisins, contain some water. (Fig. 26.) Although the carbohydrates of fruits are largely in the form of sugars easily digested and valuable as fuel, this kind of food is especially valuable for its rich supply of ash, including the compounds of calcium, magnesium, potassium, phosphorus, and iron. The iron is of great importance, being in a form much more useful to the normal processes of the body than that prescribed medicinally. The bulk given by cellulose, and the laxative property of fruit acids also are safeguards against constipation, especially in a meat diet. Fruit is the best possible dessert after a hearty meat dinner.

The digestibility of fruit is increased for some people by cooking. This is probably due to the softening of the fiber, to the destruction of any bacteria present, and in the case of the banana, to the cooking of the starch. Fruit juice can be taken by little children and invalids who might find the fiber troublesome. Some people cannot eat berries on account of irritation caused by the seeds. In this case, juice may be squeezed from cooked berries and used for beverages and jelly.

How to buy.—Since we should eat fruit daily, and not merely as a “treat,” it is important to practice economy in buying it. Fresh fruits in season, and dried fruits are the cheapest. Canned fruit is economical when it is a product of one’s own garden, or put up when some fruit has a low market price. Prices are so variable, even with one variety, that no definite sum can be given as a fixed price. Apples vary from fifty cents a bushel near the orchard and in season, to ten cents apiece for a fancy table variety in the winter. When you buy fresh fruit, inquire the prices of the many kinds offered, note which is cheapest, and then observe whether the cheaper kind is such because it is abundant, or because it is of inferior quality. If you chance to want apples for cooking, and the only cheap apples are spotted and bruised, then buy dried apples, or even canned. It is best to decide upon the fruit after you have studied market conditions rather than before.

GENERAL METHODS AND RECIPES

The preservation of fruit and other foods has been a household industry for generations, and it is now an important commercial industry. The old-time farm had its smokehouse where hams and beef were “cured,” the barrel of brine stood in the cellar for pork and corned beef, apples and corn were dried for winter use, and rows of preserve jars stood upon the shelves. Food was preserved by simple processes long before the reason for the decay and spoiling of food was fully understood, but with larger knowledge and better appliances, we now preserve food more effectively and in quantities larger than were possible in former days.

Fruit is the food material now most commonly preserved in the home kitchen. Vegetables need to be subjected to heat for a much longer time than fruit, and many people prefer to buy canned vegetables rather than to go to the trouble and expense of canning them at home. Where there is an oversupply of vegetables in the home garden, it is sometimes economy to can them, and this may be done if care is exercised. The cost of fuel and labor must be counted in, when studying the question of home preserving versus buying the canned product.

Whatever the food material, and the process, the principles of preservation are the same for all.

Why does food spoil?—The decay and moldiness of fresh fruit are matters of common observation; and the housekeeper knows that mold is liable to cover the top of a jelly glass, and that a can of fruit will ferment at times, even to the point of bursting the can.

We recognize another kind of deterioration in meat and fish that have become tainted, even when no mold is visible, and there is no opportunity for ordinary fermentation. The microscope has given us eyes to see, and as a result of the patient work of the scientist with this instrument we now know that the difficulties in keeping food are caused by the presence of minute vegetable organisms known as molds, yeasts, and bacteria. It is impossible in some cases to draw a sharp line between these different forms of lower life, yet we are able to distinguish them sufficiently for practical purposes.

Masses of mold that can be seen with the naked eye are distinguished by a feathery appearance and bright color. Figure 28 shows three species of the green mold that affects jam and jellies. Other species are found in Roquefort and Camembert cheese, and give the flavors characteristic in these cheeses.

The presence of yeast can be detected by its action, but it cannot itself be seen without the microscope. When canned fruit or homemade fruit juice “works,” yeasts cells are present in great number. Figure 29 shows one form of yeast, highly magnified, and Fig. 30 shows a single yeast cell. The yeast cake is a mixture of thousands of such cells with some flour or flour and meal, and the cells lie dormant in the cake, until we are ready to use them in bread. (See Chapter XII.) The actual yeast, however, is what Fig. 30 shows it to be, a tiny, one-celled plant, increasing in number by the division of the single cell, or by the budding out of one cell from another. When conditions are favorable the yeast cells increase in number with great rapidity, and some of the sugar that is present is broken down into carbon dioxide gas and alcohol. It is this gas that causes the familiar bubbling when fermentation is taking place. We put yeast cells into bread and cultivate it for this gas. But how does it occur in canned fruits, when its presence is not desired? Wild yeast floats in the air, and lies upon the surface of fruit. All cultivated yeast has been derived from wild yeast. In old-fashioned ways of bread-making no yeast was introduced, a soft dough being left in a warm place to ferment naturally, the yeast cells probably being present in the flour. The yeast that spoils the canned fruit is present in the fruit, in the utensils, or can, and has not been killed as it should be in the canning process.

The bacteria are also one-celled microÖrganisms, smaller than the yeast. Figure 31 shows the four types of bacterial cells. Their size is measured by the unit used in the microscope, called the micron, which is about ¹/₂₅₀₀₀ of one inch. Bacteria may measure from one to three or four of these microns in length. Some bacteria are reproduced by means of spores which form within the cell. Bacteria, as they develop in some material, produce substances from the material that may or may not be injurious to us. One important truth about the bacteria is this: that many of them are harmless, and may even be made useful, as in the manufacture of fruit vinegar. The pleasant acid of buttermilk and of sour milk is due also to bacteria which are not harmful to us. However, there may be disease producing bacteria present in milk that is not clean, and their presence must not be tolerated. Other bacteria, developing in meat and fish, produce substances known as ptomaines, which are dangerous poisons; or, more often, the kinds of bacteria which thrive in meats and fish may themselves be directly injurious to man.

It is evident, therefore, that the problem before us is the control of these lower organisms, that we may increase or destroy them as we will.

The control of microÖrganisms.—With warmth, water, and food all living things flourish and grow; most organisms require air, but some of the microÖrganisms do not. Where these conditions are best met, the organism is most active and multiplies most rapidly. To retard growth or to destroy life, the conditions must be the reverse of favorable. While warmth, say a temperature from 70° to 90° F., promotes the life of most microÖrganisms, intense heat destroys it. The boiling temperature, 212° F., will kill these lower organisms, although this heat has to be continued for some length of time, particularly in the case of spores. The spores of certain bacteria are quite resistant. A temperature of 32° F. and lower retards growth, but it requires extreme cold to destroy bacteria. Since moisture is necessary to all the lower organisms, they do not develop in a dry material or dry place.

We cannot destroy these lower forms of life by removing food from them, since they are ever present, but we can make the food unavailable to them through the introduction in the material of certain substances called preservatives which prevent their growth. The preservatives long familiar are salt, sugar, wood-smoke, spices, vinegar, and alcohol. While a small amount of sugar is necessary in the fermentation process, a large amount acts as a preservative, as in candied fruit. It is an interesting fact that alcohol and vinegar, products of fermentation processes, tend (when sufficiently concentrated) to stop the growth of the fermentation organisms.

To the reader who desires a fuller account of the bacteria, yeast, and molds, especially as related to household affairs, Buchanan’s “Household Bacteriology” is recommended as the most recent and satisfactory book in this field.

A word about buying canned goods.—When canned goods are put up in large quantities at the factory, abuses are likely to exist. Poor, even decayed, fruit may be used, the whole process may be unclean from beginning to end, and undesirable preservatives or an excess of sugar or spice may be introduced to cover the use of poor materials or methods. The condition of the worker in the cannery is one of the important industrial problems at the present time. Unhappily, poor conditions do often exist in canneries that turn out a cheap product. On the other hand, there are firms that may well take pride in their system from beginning to end.

Serving canned food.—All canned food should be exposed to the air for a short time before serving, and stirred that the material may be aerated. This partially removes a certain flatness of taste. Canned fruit is improved by reheating, even.

When possible, vegetables bought in a tin can should be washed in the colander before they are heated. This greatly improves the flavor.

GENERAL METHODS AND RECIPES

EXERCISES

1. Explain the value of fruit in the diet.

2. Why is cooked fruit sometimes better than raw?

3. Inquire the price of fresh fruit in the market, and compute the cost of a 100-Calorie portion of two of the most common and cheapest.

4. The same with one or two of the dried fruits.

5. What are the important points in the preparation of fresh fruit for the table?

6. What changes are effected in baking an apple?

7. What are the principles of the preservation of food?

8. What is meant by a preservative?

9. What is meant by sterilization?

10. What is mold? Decay? Fermentation?

11. What are the important points in canning?

12. What is the difference between canned fruit and “preserves”?

13. How does jelly making differ from the other processes?

14. What is one of the most important points in cooking dried fruits?

15. Find the cost of a can of peaches at the grocery. Weigh the contents and count the peaches. Compare with the cost of an equal amount of home-canned peaches. What points in the problem must be taken into account?

16. The same problem with jelly bought at the grocery and made at home.

17. Work out the problem of estimating the comparative cost of canned peaches and dried peaches, when calculated to the same food value.