Most jam recipes contain four basic components:
- pureed fruit and/or vegetables and their juices
- some type of acid (lemon juice or vinegar)
- a sweetener (sugar, sugar substitute)
- a thickener (pectin from a package or fruit, or cooking time)
Spices and other flavorings are optional.
Those four basic components are completely flexible, so feel free to substitute what you have into a basic recipe to create your own signature jams. Do be aware of the amount of natural pectin in your main ingredient (puree), and be prepared to supplement the natural pectin with granulated or liquid pectin where needed. Sugar can safely be reduced by up to half of the listed amount in most published jam recipes, if you are going to process the jam in a boiling water bath, freeze it or eat it immediately.
Old or new, most jam recipes are also proportional: to X cups of fruit and juice, add Y cups of sugar and a fixed amount of acid. Packaged pectin is a newer addition, which helps with texture and eliminates long cooking. While it’s easiest to handle small batches of jam in the modern kitchen, most recipes can be safely doubled if you have the space to keep all of the empty jars hot, (try the dishwasher!) and fill and seal them quickly.
For quick jam references online, make sure to refer to the Blogs & Websites link, and to my posts Online Jam and Bookshelf Jam. You can also consult your local cooperative extension or the USDA website.