EXPERIMENT 94: PECTIN IN FRUIT JUICE.—Put a few grapes, slices of apple, or cranberries in a small saucepan, and add enough water to cover and cook until the fruit is tender and soft enough to mash. Strain the cooked fruit through cheese-cloth.

Put 1 teaspoonful of the extracted fruit juice in a saucer, add an equal quantity of alcohol. [Footnote 126: Either grain (ethyl), wood (methyl), or denatured alcohol may be used. Both wood and denatured alcohol are poisonous. If they are used for testing, they should be handled and stored away with caution.] Mix by gently rotating the saucer. Let the mixture stand for 5 minutes. Then examine. What change has taken place in the fruit juice?

The formation of a solid mass in the mixture of fruit juice and alcohol which has stood for 5 minutes indicates that the fruit juice contains pectin,—a vegetable gelatine.

EXPERIMENT 95: PECTIN IN THE INNER PORTION OF ORANGE OR LEMON PEEL.—Cut away the yellow portion from orange or lemon rind. Cut or chop the white portion of the rind in small pieces. Cover with water and soak several hours or overnight. Then cook slowly for 1/2 hour. Strain and set aside to cool. To 1 teaspoonful of this liquid add an equal quantity of alcohol, and proceed as in Experiment 94. Does the lemon or orange rind contain pectin?

THE PRINCIPLE OF JELLY MAKING.—When the juices of certain fruits are extracted and cooked with sugar, the mixture stiffens when cool. This property of stiffening is due to the presence in fruit of two materials,— a certain carbohydrate, called pectin, and an acid. Pectin is like starch in that it stiffens when cold; but like sugar, in that it is soluble. Not all fruits contain pectin.

Jelly is most easily prepared from fruits which are rich in pectin and contain some acid. Unless pectin is contained in the fruit, the addition of sugar to fruit juice will not cause the juice to jelly. But jelly may be made from a fruit lacking in pectin, if it is combined with a fruit rich in pectin.

Certain fruits contain pectin, but are lacking in acid, hence are not good for jelly making. These fruits can be used for jelly, however, if acid is added.

SELECTION OF FRUITS FOR JELLY MAKING.—For jelly making, choose fruits which contain considerable pectin and some acid. The fruits should be fresh and not over-ripe. Some "green" fruits make fine jelly. Currant, crabapple, grape, apple, and plum are good jelly-making fruits.

If it is desirable to use a fruit containing little pectin, as strawberries, add a fruit rich in pectin, as currants. If about 10 per cent of the fruit which contain much pectin is added to the other fruit, the flavor of the foundation fruit is not much altered.

If it is desired to use a fruit containing pectin but deficient in acid, as sweet apple and quince, add tartaric or citric acid. Since the acidity of fruits varies, no definite quantity of acid can be stated. It has been suggested [Footnote 127: See University of Illinois Bulletin, "Principles of Jelly Making," p. 249.] that enough acid should be added to make the fruit juice about as acid to taste as good tart apples. At least one teaspoonful of acid is required for one quart of fruit juice. Dissolve the acid in the fruit juice, then taste the mixture. If necessary, add more acid to produce the acidity indicated above. Jelly may be prepared from strawberries, peaches, and pears by the addition of these acids, but the flavor is somewhat impaired.

The suggestion has been made also [Footnote 128: Idem, p. 25.] that the inner white portion of lemon or orange peel be used as a source of pectin with fruit deficient in pectin. Remove the yellow portion of the rind, put the white portion through a food chopper, and soak in water for several hours or overnight. Then cook slowly for several hours. Strain out the solid portion. Add the liquid to the fruit juice deficient in pectin and use for jelly making. The rind of lemons and oranges may be dried for use in jelly making. When desired for use, soak and cook as directed above.

GENERAL METHOD OF JELLY MAKING

Wash and pick over the fruit; remove the stems, but use the skin and seeds and thus retain as much of the fruit as possible. The skin of fruit usually adds color to jelly. If large fruit is used, cut it in pieces. Cook the fruit slowly in water. Use very little water for juicy fruits, such as currants and raspberries,—1 cupful of water to 4 or 5 quarts of fruit. Crush the fruits during cooking.

To cook large fruits requires water. A general proportion is half as much water, by measure, as prepared fruit. A little less water may be used for peaches and plums and a little more for winter apples. A fair estimate is 3 quarts of strained juice from 8 quarts of fruit and 4 quarts of water. If the quantity of juice is greater than this, it should be boiled down to 3 quarts before adding the sugar.

When the fruit is cooked until it is very soft, it is ready for straining. For straining, make a bag of double cheesecloth or flannel. Wring the jelly bag out of hot water and suspend it from a strong support. Pour the cooked fruit into the bag and let the juice drip into a bowl. If transparent jelly is desired, do not press the juice through the bag; let the juice drip for several hours or overnight.

Measure the clear fruit juice and heat it. The time of cooking depends upon the per cent of pectin and the acidity of the juice; the more pectin and acid, the less the time of cooking. The time varies from 8 to 30 minutes. Skim the juice when necessary. While the juice is cooking, measure three fourths as much sugar [Footnote 129: The quantity of sugar used in jelly making depends upon the quantity of pectin in fruit juice,—the more pectin, the more sugar. A most satisfactory method of determining the quantity of pectin and consequently the quantity of sugar to use with fruit juice is suggested by the Bulletin of the National War Garden Commission. The test follows: To a tablespoonful of fruit juice which has been boiled and cooled, add 1 tablespoonful of alcohol (see footnote 126.). Mix by gently rotating and then let stand. If a solid mass forms, use equal parts of fruit juice and sugar. If 2 or 3 masses form, use 2/3 to 3/4 as much sugar as juice. If several small solid particles form, use 1/2 as much sugar as juice. If no solid particles form, the fruit juice should be enriched by the addition of some pectin-rich fruit juice.] as fruit juice and heat the sugar. For currants and green or under-ripe grapes, use equal quantities of sugar and fruit juice. Add the hot sugar to the boiling sirup and cook. The following are tests for sufficient cooking of jelly.

(a) Coats the spoon.

(b) Falls from the spoon in heavy drops. [Footnote 130: Two drops forming side by side along the edge of the spoon has been found to be a reliable test.]

(c) Stiffens when dropped on a cold dish and allowed to cool.

The first two tests are more satisfactory than the last, since the cooking process may be carried too far while the "test-jelly" is cooling.

Seal as Jam or shred paraffin and place it in the bottom of sterilized jelly glasses. Pour the hot jelly into the glasses and set aside to stiffen. Then cover and store. It is well to store jelly in a cool, dry, and dark place. The color of fruit sometimes fades when kept in a light place.

Long cooking of pectin changes it into substances which do not have the property of jellying, hence, make jelly in as short a time as possible. The purpose of heating the sugar is to hasten the process of jelly making. The addition of cold sugar would cool the mixture and thus prolong the process.

The addition of too much sugar is often the cause of unsuccessful jelly making. Crystallization of the sugar from the jelly may result from an excess of sugar.

The fruit pulp left in the jelly bag should be utilized. Marmalade may be made from it, or more jelly can be prepared from it. To accomplish the latter, add water to the fruit pulp (enough to cover), mix, and heat slowly until the boiling point is reached. Strain and prepare jelly from the juice. However, more cooking of the juice before the sugar is added is required for the second extraction, since the juice contains so much water. The juice extracted for a third time from most fruits will contain enough pectin for jelly making. It has been found that more desirable jelly can be obtained by this method than by pressing the juice from the bag and thus obtaining what is termed "second quality" jelly.

FRUIT JUICES WITHOUT SUGAR.—Extract the juice from fruit as directed in General Method of Jelly Making. Do not add sugar to the juice. Can it as directed in (a) or (b).

(a) Reheat until the boiling temperature is reached, then pour into sterilized jars. Fill to overflowing and seal.

(b) Place the juice in sterilized jars. Partially seal and place in a water bath having the water reach the neck of the jar. Let it cook at a simmering temperature from 20 to 30 minutes. Remove from the water bath, and seal securely.

In the winter time or when desired for use, this fruit juice may be made into jelly as directed in General Method of Jelly Making, or it may be sweetened, diluted if necessary, and used as a beverage. This method of preserving fruit juice is especially desirable when there is a scarcity of sugar.

[Illustration: FIGURE 92—THE COMPOSITION OF FRUITS AND FRUIT PRODUCTS.
(Revised edition.)]

QUESTIONS

Note the difference in the quantity of carbohydrates in Canned Fruit and Fruit Jelly (see Figure 92). What kind of carbohydrate is present in greatest quantity in these foods?

To what is the difference in flavor of Canned Fruit and Fruit Jelly largely due?

What is the chief difference in the processes of jam making and jelly making?

What is the result if too much sugar is used in jelly making?

What is the result if jelly is cooked too long?

Note the difference in the methods of sealing jams and jellies. Explain.