The plant carbohydrate pectin is used as a gelling and thickening agent in the manufacture of food products like jams and jellies. It is made by processing fruits and vegetables, including plums, citrus fruits, apples and quince. Pectin can be extracted from citrus fruits such as lemons, limes, grapefruits and oranges, but regardless of what fruit is used, the basic method is the same.
Collect only the peel of the lemon. Using a sharp paring knife, carefully cut a small layer of the lemon peel, including the bitter white parts. These areas are highly concentrated in pectin.
Weigh the prepared peels. About 907 g (2 lb) of coarsely chopped peel will be needed. The peels can be wrapped in a muslin square and tied up to make a pouch so that cooking them is less messy.
Boil the peel. In a large saucepan or pot filled with about 0.7 litres (1 1/4 pints) of boiling water, place the muslin pouch of lemon peels in and reduce the heat so that the water is simmering. Allow the peels to cook for approximately 40 minutes until they soften to a pulp-like consistency. Remove the muslin bag and squeeze the pulp through a jelly bag to extract all of the pectin.
Collect and test the pectin. The pectin strength is measured by mixing 3 tsp of methylated spirits, grain alcohol or denatured alcohol with 1 tsp of pectin extract. Let this cool and then discard the methylated spirits by decanting it away. If the pectin is ready to use, a gel-like clot would have formed; however if it is not ready, the clot will disintegrate into smaller pieces and the pulp must be cooked for an additional 10 to 15 minutes before it can be used. The pectin can then be transferred to airtight containers and stored.
Do not consume the grain or denatured alcohol.