Pectin, which comes from the cell walls of plants, is used as a primary gelling agent in many james and preserves. Most jam makers go to grocery stores to purchase pectin in powder form, but it's much healthier to make it yourself. Check out this video to learn how to produce pectin from underripe green apples.
San Francisco-based Shakirah Simley, owner of Slow Jams, does not encourage the use of store-bought pectins. Make your own, she (lovingly) taunts.