There are two ways to test jelly for doneness. For the temperature test, simply use a jelly or candy thermometer to boil the mixture until it reaches the temperature specified for the altitude where you live.
Chart From United States Department of Agriculture
Home canning your own jam and jelly is a great way to put your fruits to tasty use. Use this article to learn how to make jelly and jam, with and without pectin, the substance that causes a gel to form when combined with the correct amounts of acid and sugar. While pectin is found in all fruits, some fruits, such as apples and plums, have enough natural pectin to gel without any additional mixed in, while other fruits, such as strawberries and blueberries, need help from other high-pectin fruits or a pectin supplement. Confused? Don’t be. With this helpful excerpt from the United States Department of Agriculture's Complete Guide to Home Canning, you'll learn the step-by-step process for home canning jam and jelly. Use this and our other canning resources to stock up after your harvest.
The following is an excerpt from the USDA Complete Guide to Home Canning, detailing why and how you should make canning syrup to preserve your fruit.
Making Jelly Without Added Pectin
Use only firm fruits naturally high in pectin. Select a mixture of about 3/4 ripe and 1/4 underripe fruit. Do not use commercially canned or frozen fruit juices. Their pectin content is too low. Wash all fruits thoroughly before cooking. Crush soft fruits or berries; cut firmer fruits into small pieces. Using the peels and cores adds pectin to the juice during cooking. Add water to fruits that require it, as listed in the table of ingredients below. Put fruit and water in large saucepan and bring to a boil. Then simmer according to the times below until fruit is soft, while stirring to prevent scorching. One pound of fruit should yield at least 1 cup of clear juice.
Extracting Juices and Making Jelly
When fruit is tender, strain through a colander, then strain through a double layer of cheesecloth or a jelly bag. Allow juice to drip through, using a stand or colander to hold the bag. Pressing or squeezing the bag or cloth will cause cloudy jelly.
Using no more than 6 to 8 cups of extracted fruit juice at a time, measure fruit juice, sugar, and lemon juice according to the ingredients in the table in the Image Gallery and heat to boiling. Stir until the sugar is dissolved. Boil over high heat to the jellying point. To test jelly for doneness, use one of the following methods:
Temperature Test. Use a jelly or candy thermometer and boil until mixture reaches the temperatures specified for the altitude in which you live, as detailed in the chart in the Image Gallery.
Sheet or Spoon Test. Dip a cool metal spoon into the boiling jelly mixture. Raise the spoon about 12 inches above the pan (out of steam). Turn the spoon so the liquid runs off the side. The jelly is done when the syrup forms two drops that flow together and sheet or hang off the edge of the spoon.
Remove from heat and quickly skim off foam. Fill sterile jars with jelly. Use a measuring cup or ladle the jelly through a wide-mouthed funnel, leaving 1/4-inch headspace. Wipe rims of jars with a dampened clean paper towel. Adjust lids and process.
Making Jam Without Added Pectin
Wash and rinse all fruits thoroughly before cooking. Do not soak. For best flavor, use fully ripe fruit. Remove stems, skins, and pits from fruit; cut into pieces and crush. For berries, remove stems and blossoms and crush. Seedy berries may be put through a sieve or food mill. Measure crushed fruit into large saucepan using the ingredient quantities specified in the table in the Image Gallery.
Add sugar and bring to a boil while stirring rapidly and constantly. Continue to boil until mixture thickens. Use one of the following tests to determine when jams and jellies are ready to fill. Remember to allow for thickening during cooling.
Temperature Test. Use a jelly or candy thermometer and boil until mixture reaches the temperature for your altitude.
Refrigerator Test. Remove the jam mixture from the heat. Pour a small amount of boiling jam on a cold plate and put it in the freezing compartment of a refrigerator for a few minutes. If the mixture gels, it is ready to fill.
Remove from heat and skim off foam quickly. Fill sterile jars with jam. Use a measuring cup or ladle the jam through a wide-mouthed funnel, leaving 1/4 inch headspace. Wipe rims of jars with a dampened clean paper towel. Adjust lids and process. See the Image Gallery for recommended process times for jams and jellies with or without added pectin.
Making Jams and Jellies With Added Pectin
Fresh fruits and juices as well as commercially canned or frozen fruit juice can be used with commercially prepared powdered or liquid pectins. The order of combining ingredients depends on the type of pectin used. Complete directions for a variety of fruits are provided with packaged pectin. Jelly or jam made with added pectin requires less cooking and generally gives a larger yield. These products have more natural fruit flavors, too. In addition, using added pectin eliminates the need to test hot jellies and jams for proper gelling. Adding 1/2 teaspoon of butter or margarine with the juice and pectin will reduce foaming. However, these may cause off-flavor in long-term storage of jellies and jams. Recipes available using packaged pectin include:
Jellies: Apple, crab apple, blackberry, boysenberry, dewberry, currant, elderberry, grape, mayhaw, mint, peach, plum, black or red raspberry, loganberry, rhubarb and strawberry.
Jams: Apricot, blackberry, boysenberry, dewberry, loganberry, red raspberry, youngberry, blueberry, cherry, currant, fig, gooseberry, grape, orange marmalade, peach, pear, plum, rhubarb, strawberry and spiced tomato.
Be sure to use pre-sterilized Mason canning jars, self-sealing two-piece lids, and a 5-minute process (corrected for altitude, as necessary) in boiling water, to prevent spoilage of jams and jellies.
Purchase fresh pectin each year. Old pectin may result in poor gels. Follow the instructions with each package and process using the times recommended in the Image Gallery.