Notes About Pectin for Making Homemade Jam
Pectin is a naturally occurring substance (a polyscaccaride) found in berries, apples and other fruit. When heated together with sugar, it causes a thickening that is characteristic of jams and jellies.
Your grandmother probably didn't use pectin. Instead she stood over a hot, boiling pot, stirring and getting splattered by hot jam until she cooked the vitamins out of it and it finally cooked down to a thicker consistency.
Most pectin you buy at the supermarket is produced in Europe an imported. It has a limited shelf life; usually you don't want to keep it from year to year, as it's ability to gel will decrease.
After the jam has been heated and starts to cool, a gel starts to form.
Gelling problems
Too stiff or lumpy jam
If gel formation is too strong, due to way too much pectin, the jam becomes stiff, lumpy or granular in texture.
Cooking too long, but not at a high temperature, can boil off water, without breaking the pectin down. This results in jam that is too stiff.
This also occurs if the temperature is too high, for too long, or the jam is not stirred frequently.
Using underripe fruit, which has more pectin than ripe fruit, with the same amount of pecton as the recipe requires for ripe fruit, also makes stiff jellies and jams. FYI, commercial pectin is intended for use with fully ripe (but not overripe) fruit.
Runny Jam
Undercooking (it must hit a full rolling boil for ONE minute) or too little pectin or sugar leads to runny jam.
Overheating - that is too high temperatures or uneven heat distribution builds excess heat which causes the pectin to break down. This is why you shouldn't double batches - due to inherently uneven heating of home cookware - commercial canning equipment is design to heat more uniformly.
The chemistry of the gel
If you are interested in the chemistry of a gel, Wikipedia tells us that in
"high-ester pectins at soluble solids content above 60% and a pH-value between 2.8 and 3.6, hydrogen-bonds and hydrophobic interactions bind the individual pectin chains together. These bonds form as water is bound by sugar and forces pectin strands to stick together. These form a 3-dimensional molecular net that creates the macromolecular gel. The gelling-mechanism is called a low-water-activity gel or sugar-acid-pectin gel. In low-ester pectins, ionic bridges are formed between calcium and carboxylic acid of the galacturonic acid. This is idealized in the so-called “egg box-model”. Low-ester pectins need calcium to form a gel, but can do so at lower soluble solids and higher pH-values than high-ester pectins."
Effectively, pectin's structure binds with water in an acid environment. Sugar increases pectin's ability to gel, and affects the texture and consistency of jellies and jams as they cool and set. Note: sugar is not key to the preservation of the jam - the sterile environmental and acidity are more important.
Pectin concentrations vary in fruit.
High pectin content fruits:
Citrus skins (oranges, tangerines, grapefruit, lemons, limes, etc. - the pectin is high in the skin but low in the fruit), tart cooking apples, crab apples, most plums, lemons, and wild grapes (Eastern Concord variety), cranberries, gooseberries and boysenberries are high in pectin. I've also found that blackberries are very high in pectin.
Medium pectin fruits:
Apricots, rhubarb, quince
Low pectin fruits:
Sweet cherries, sour cherries, grapefruit, grape juice, grapes (other than wild and Concord types), melons, and oranges
Very Low pectin fruits:
Nectarines, strawberries, peaches, pears, figs, apricots, elderberries, raspberries, grapes (Western Concord variety), guava, and pomegranates.
The pectin content in all fruit is also generally higher when fruit is just barely ripe and diminishes as it matures from fully ripe to overripe. The process of ripening involves the breakdown of pectins, which softens the fruit as it ripens. Apples and crabapples (especially unripe ones) are good sources of pectin and are often used in making commercial pectin. Some commercial pectin is made from citrus peels.
Testing for Pectin
There is a test that uses rubbing alcohol to provide a rough indication of the amount of pectin in the fruit. Mix 1 teaspoon of cooked, cooled crushed fruit with 1 tablespoon of rubbing alcohol. Use a closed container and shake gently. Juices from fruit that is high in pectin will form a solid gelatinous lump. If the fruit is low in pectin, it will form only small rubbery particles.
It ought to be needless to say, that just as you should never put a cup of very hot coffee in your lap while driving a car, you should not eat the test mixture (that with the rubbing alcohol in it) as rubbing alcohol is a poison.
Make your own pectin?
Cookbooks from 50-100 years ago often have recipes for extracting pectin from apples for use in other jams and jellies. You may have noticed that old jam recipes often include some lemon peel for the pectin content, and jelly recipes from the pre-SureJell and Certo era are usually essentially apple jelly with other fruit for flavor. Aside from strawberries and blackberries, few other fruits have enough pectin to make self-jelling preserves.
How much pectin to use?
Pectin needs the proper ratio acidity and sugar to make the jams or jellies set. As pointed out at the top of this article, these proportions vary according to the fruit you're using. Using the recipes I've provide, and the proportions of pectin and sugar listed in the specific instructions that come with the particular pectin that you use, gives a much higher quality jam than if you just wing it.
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