Types of Commercial Fruit Pectin
Pectin is available in two forms: liquid and powdered (dry). Although both products are made from fruit, they're not interchangeable. Be sure to use the correct type and amount of pectin called for in your recipe.
Using Liquid Fruit Pectin
Liquid pectin is usually made from apples. Today, a box contains two 3-ounce pouches. The most common brand is Certo.
Liquid fruit pectin was originally sold in 6-ounce bottles. Older recipes may call for "one-half of a bottle." If you read a pouch of liquid pectin today, it states "1 pouch equals 1/2 bottle."
Because you have to add your liquid pectin at the specified time and temperature, have it at the ready: Cut off the top of the pouch and stand it in a measuring cup or other container to keep it from spilling. Then, when it's time to add the liquid pectin, add it all at the same time squeezing the pouch with your fingers like you do to get the last bit of toothpaste out of the tube.
Using Powdered (dry) Fruit Pectin
Powdered pectin is made from citrus fruit or apples. It comes in a box similar to a gelatin or pudding mix box and contains 1 3/4 ounces (the most commonly used size) or 2 ounces. Use the size stated in your recipe ingredients and add it before you heat the fruit mixture.
In addition to different sizes, powdered pectin comes in two varieties: fruit pectin for homemade jams and jellies, and fruit pectin for lower sugar recipes. Use the variety your recipe calls for; they're not interchangeable.