You can capture the essence of summer’s fresh peaches in your own homemade jelly and enjoy the flavor even when the peach harvest is a distant memory. Pectin is an acidic thickener, available at your grocer’s, but you can make peach jelly without it if you adapt your recipe. A naturally occurring substance in fruits, pectin is essential for producing a gelatin-like consistency in jellies, but that doesn’t mean you have to add it separately. You can increase the fruit's own pectin levels, and use lemon juice to boost the setting power.
Make Peach Juice
Use under-ripe peaches at the ratio of one part under-ripe peaches to three parts ripe peaches. Natural pectin occurs in all fruits, but it is more prominent in under-ripe fruit. For example, if you’re making jelly from eight large peaches, two of those peaches should be under-ripe, and the other six can be ripe.
Boil jars and lids in a large stockpot for 5 minutes to sterilize them. Use tongs to remove the jars to a clean dishcloth on the countertop.
Peel, pit and dice all the peaches. Put them in a large, heavy saucepan.
Cover the peaches with water and bring the mixture to a boil over medium heat. Reduce the heat to low and simmer for 20 minutes.
Cool the peach mixture before straining the liquid through several thicknesses of cheesecloth or a fine kitchen sieve. Discard the pulp or use it to make peach jam. Save the peach juice to make your jelly.
Make the Jelly
Measure 6 cups of peach juice into a large saucepan and add 7 cups of sugar.
Bring the juice to a boil, stirring constantly, then add 1/2 cup lemon juice. Turn the burner to low and simmer for 10 minutes. As the liquid simmers, foam may rise to the top -- skim this off with a spoon.
Remove the pan from the burner and ladle the hot liquid carefully into the prepared jars to within 1/4 inch of the rim. Wipe off the rim with a clean damp cloth before putting the lids on the jars.
Process the jars by boiling them in a water bath for 10 minutes. You can make a water bath by filling a large stockpot with enough water to cover the tops of the jars by at least 1 inch. Use tongs to move the jars into and out of the hot water.
Place processed peach-jelly jars on a clean dishcloth on the countertop. Wipe water off the lids before tightening them. Do not move the jars for at least 24 hours. As the jelly cools, the centers of the lids will draw downward, forming an airtight seal that will protect your jelly.