Pectin is a sugar found in the walls of plants that can be used as a gelling agent, especially in jams and jellies. Although many plants have pectin, the peel of citrus fruits such as oranges is particularly rich in pectin. According to a 2011 article in the "Indian Journal of Natural Products and Resources," as much as 30 percent of citrus peel is composed of pectin. You can buy pectin from a store, and you can also extract it from orange peel.
Peel the oranges. Keep as much of the white membranous part of the peel as possible, since this is particularly high in pectin.
Cut the orange peel into narrow strips and use a knife to remove the white part of the peel, also known as the pith.
Dice the pith into small pieces.
Add 2 tablespoons of lemon juice to the chopped pith. You can allow this mixture to sit for one hour or move onto the next step, depending on how much time you have.
Add the water to the pith and lemon juice mixture and let sit for one hour.
Bring the mixture of water, pith and lemon juice to a boil and then let it simmer. If you allowed the pith and lemon juice mixture to sit for one hour prior to adding water, you can simmer for only 10 minutes. If not, simmer for 20 minutes.
Pour the mixture into a jelly bag or a strainer lined with cheesecloth and allow it to drain overnight. Pressing on the solids will allow you to extract more juice but may also make your pectin cloudy.
Test the drained liquid for pectin content. To do this, mix 1 tablespoon of rubbing alcohol and 1 tablespoon of the drained liquid in a small jar with a lid and shake. Let it stand one minute and examine the contents of the jar. If the mixture has formed one jelly-like mass, the juice has a high pectin content. Several smaller lumps indicate medium pectin. If there are a lot of little lumps, you may not have enough pectin to make jelly. If you desire a higher pectin concentration, simmer the drained liquid until half the liquid has evaporated and retest the resulting liquid for pectin content.