Michigan State University Extension
Preserving Food Safely - 01600545
A rough estimate of the amount of pectin in fruit juice may be obtained through a cooking test or the use of rubbing alcohol or a Jelmeter.
Cooking Test. Measure 1/3 cup of juice and 1/4 cup of sugar into a small saucepan. Heat slowly, stirring constantly until all the sugar is dissolved. Bring the mixture to a boil and boil rapidly until it passes the sheeting test. Pour the jelly into a clean, hot jelly glass or a small bowl and let cool. If the cooled mixture is jelly-like, your fruit juice will jell.
Alcohol Test. Add 1 teaspoon cooked, cooled fruit juice to 1 tablespoon of rubbing alcohol. Stir slightly to mix. Juices rich in pectin will form a solid jelly-like mass that can be picked up by a fork. Juices low in pectin will form small particles of jelly-like material.
NOTE: Rubbing alcohol is poisonous. Do not taste the tested juice. Wash all utensils used in this test thoroughly.
Jelmeter Test. A Jelmeter is a graduated glass tube with an opening at each end. The rate of flow of fruit juice through this tube gives a rough estimate of the amount of pectin in the juice.
If a test indicates that the juice is low in pectin, use a recipe calling for the addition of powdered or liquid pectin.