Pectin Extract

Source: Complete Guide to Home Canning, USDA

A pectin concentrate or extract can be made from fruits that are very
high in pectin. Add the concentrate to any jelly stock that gives a
low pectin test, mix well, then retest to determine the amount of
sugar needed. Usually 4 to 6 tablespoons of the extract to 1 cup of
juice is enough to give good jellying qualities.

Crab Apple Pectin Extract

1 pound sliced unpeeled crab apples
1 1/2 cups water

Cook slowly for 1/2 or 3/4 hour, press the juice through a cloth bag,
then allow this juice to drain without pressure through a heavy flannel jelly bag. Pectin can be sealed and processed 15 minutes in a waterbath at boiling temperature. Label and store until needed for jelly making. Pectin may be frozen to save for future use.

Jellies Using Homemade Pectin Extract

Peach
Pear
Strawberry
Any other juice showing low pectin test

To any juice which gives a low pectin test – add pectin extract at the rate of 4 to 6 tablespoons per cup of juice. Mix well and make pectin test. Add sugar as indicated by pectin test; then follow general directions for making jelly.