Date: May 1989 (Revised April 1995)
Source: University of Wisconsin
This is the old way of making jelly and it's still a very good way, provided the fruit is rich in natural pectin. Crab apples, green apples, sour cherries, and Concord grapes are examples of such fruit. You use less sugar with this method, but you must boil the mixture for a longer time and you end up with less jelly.
If you are not sure if a fruit has enough pectin, make this test: pour one tablespoon of the cool fruit juice and one tablespoon denatured alcohol into a cup. Examples of brands are E2, Dalox, Solex--are available at paint and hardware stores. Stir slightly and let stand for 2 minutes. If a solid mass of jelly forms, the fruit has a high pectin content. In this case, use one cup sugar for each cup of juice when you make jelly.
If several small jelly-like pieces form, however, the pectin content of the fruit is only moderate. Use only a 3/4 cup of sugar for each cup of juice. If the mixture forms small particles, the fruit has too little pectin to make jelly unless you add commercial pectin. In any case, do not taste the mixture as it is not for human consumption. Just throw it down the drain and wash equipment well.
If the fruit contains enough pectin, measure it into a large pot and bring juice to a boil. Add a measured amount of sugar stirring well until it dissolves. Boil rapidly until the mixture reaches the jellying point.
There are two simple ways to test whether jelly made without added pectin is done. The most common but least dependable way is to dip a cold metal spoon in to the boiling mixture. Hold it a foot or more above the kettle--out of the steam--and turn it sideways. If the mixture forms 2 drops that flow together and fall off the spoon in a sheet, the jelly is done.
The better test is to use a jelly, candy or deep-fat thermometer. Before starting to cook your jelly, take the temperature of boiling water. This needs to be done because boiling point varies with different altitude and the accuracy of most household thermometers are not very accurate. After boiling the jelly mixture for a while, lower the bulb into the mix and read the results. When the jelly mixture temperature is 8 degrees above the boiling water temperature, the jelly is done.
If you need further information, please contact your county office of the NDSU Extension Service.
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