In order to test fruit juice for that gelatinising agent, "Pectin," it is necessary to obtain some denatured or pure alcohol. To carry out the test, after the fruit has been cooked in the water, as directed further on, until tender, and then strained, measure one dessertspoonful of the juice into a glass, allow to cool, and then add one dessertspoonful alcohol. Leave for half an hour. If there is sufficient pectin present it will form into a jelly-like mass. If a large percentage of pectin is present it will appear in one mass or clot, which will indicate that a cup of sugar should be used to a cup of juice; but if the pectin does not slip from the glass in one mass, only three-quarters of a cup of sugar should be used to a cup of juice; and if the pectin is very thin and separated, only half a cup of sugar should be allowed to a cup of juice.
A good jelly should be bright and clear and of good colour. When removed from the glass or mould it should retain its shape, and when being cut with a spoon should make a clear, distinct cut, leaving the spoon clean; nor should it be too firm, but should be tender enough to quiver without breaking.
The best way is to use a spoon. Dip the spoon into the boiling mass and let it drop from the spoon.
Before the jellying stage is reached the syrup will run from the spoon, but as it gets near the stage, it will be seen to thicken and to drop off more slowly, until eventually the syrup will hang on to the side of the spoon in the form of drops or beads, when it is ready to be poured into dry jars, heated in the oven.