If you'd like to make the most all-natural jam, jelly, marmalade or preserve that you possibly can, you'll be interested in how to make your own pectin. Pectin is a naturally occurring substance (a polyscaccaride) found in berries, apples and other fruit. When heated together with sugar, it causes a thickening that is characteristic of jams and jellies.
Your grandmother probably didn't use commercial pectin. Instead she stood over a hot, boiling pot, stirring and getting splattered by hot jam until she cooked the vitamins out of it and it finally cooked down to a thicker consistency. Or if she was very knowledgeable, she made her own pectin. She made it from apples and while doesn't change the flavor a bit, it helped her thicken the jam faster and allowed her to use less sugar!
Tart / Green Apple Pectin
3 pounds sliced, washed tart, green apples (like Granny Smith) with peels and cores. Crabapples are the best. Small, green, immature apples of most varieties work, too.
4 cups water
2 tablespoons of lemon juice
Wash, but don't peel, about seven large tart green apples. Put them in a pot.
Cut them into pieces
Add four cups of water and two tablespoons of lemon juice.
Boil the mixture until it reduces almost in half (about 30 to 45 minutes), then Strain it through cheesecloth or a jelly bag.
Boil the juice for another 20 minutes,
Pour it into sanitized jars, and seal them to store in the refrigerator, freezer or process in a water bath.
How much to use?
That is the big question... and difficult to answer. The pectin content of fruit varies so much, even within a season, that almost anything I could tell you about how much of your homemade pectin to use with the fruit you picked or bought would be meaningless. Both would vary considerably.
So, instead, I'll tell you how to figure out the right formula for your own pectin. Here are the questions to answer:
How much pectin is in the fruit that you are using to make jam, jelly or preserves?
As we learned on this page about pectin, some fruits naturally have more or less pectin than others. For example, if you are making strawberry jam, you will need to use more pectin (of any kind) than if you are making blackberry jam, since blackberries naturally contain more pectin than strawberries. See this page for the pectin content of fruits.
How ripe is the fruit?
generally speaking, the more ripe the fruit is, the lower the pectin levels are.
How concentrated is your homemade pectin?
No one, but you, knows or determines this. When you make your own pectin, you're the manufacturer, you control the production line, the quality control, etc., so only you will know, largely from practice, how much of your pectin to use.
That's the bottom line! As you make the first batch, and are ready to fill the jars; first remove a spoonful of the jam, and hold an ice cube against the bottom of the spoon to cool the jam. If the spoonful sets to your liking, you can fill the jars, seal them and process them in the water bath canner. If the spoonful does not set, add another cup of sugar, 1/4 cup of lemon juice and more of your pectin, bring to a full boil for 1 minute, and test again!