Extraction
In jelly making, juice is extracted either by crushing, by limited heating using small amounts of water, or by longer cooking with measured amounts of water. Heating aids in pectin extraction for those recipes not using added pectin.
The prepared fruit is put in a damp jelly bag or several thicknesses of damp cheesecloth, tied, and hung to drip. The clearest juice will be free run, but yields increase if the bag is pressed or twisted. Re-straining this juice is recommended. Do not squeeze or press.
Jams, jellies, and preserves can be made with added pectin or without it, depending on the fruit. Fruits such as raspberries, strawberries, and peaches generally need added pectin. Apples, crabapples, currants, plums, grapes, and quinces—if not overripe—contain enough pectin and acid for good gel strength.
Pectin content can be checked visually by mixing 1 tablespoon of cool cooked fruit juice and 1 tablespoon of denatured alcohol and mixing. Fruit high in pectin will form a jellylike mass while fruit low in pectin will show little clumping. Caution: Do not taste; the mixture is poisonous.
Pectin may also be tested using a jelmeter. This graduated glass tube measures the rate of fruit juice flow through the tube, giving a rough estimate of the amount of pectin present.
Jellied fruit products made without added pectin require less sugar per fruit unit and need longer boiling to reach the end point. The yield of finished product is less than that with added pectin.
Pectin added to fruit, either in powder or liquid form, must be used in recipes designating the type. Powdered pectin is mixed with the unheated fruit juice or unheated crushed fruit.
Liquid pectin is added to the boiling fruit juice or fruit and sugar mixture. The boiling time of 1 minute for both types is used and must be accurately timed. Regardless of type, or whether pectin is used, you must follow directions closely, taking accurate measurements.