Pectin causes jams and jellies to gel. When using a pectin poor fruit, pectin must be added or the result will be nothing more than a fruit syrup. I refuse to use store bought pectin because I think it takes the craft out of jam and jelly making. Usually I just add apple skins and cores to whatever I'm making, but I thought I'd give making my own pectin a try.
The basic method is to take a pectin rich fruit and extract the water soluble pectin by boiling it, then concentrating the liquid. Apples are a good source of pectin because they both contain a lot of pectin and have a relatively neutral flavour (as opposed to orange peels for instance).
Step 1: Ingredients and tools
Pectin is concentrated in the cores and skins of all apples, and is especially strong in tart green apples. Using the cores and skins left over from making a pie is a great way to upcycle your scraps. For this instructable I used crabapples that didn't have enough flavour to bother with crabapple jelly.
3 lb Apples
4 cups Water
2 Tbsp Lemon Juice
Jelly bag/cheese cloth and strainer
I am using the basic method from www.pickyourown.org, a website with a lot of very helpful information.