Pectin is a naturally occurring carbohydrate in fruit that is concentrated in the fruit's skin and the core. When cooked, Pectin solidifies to a gel, causing fruit preserves to set.
Fruit uses Pectin to build cell walls with. Generally, unripe fruit will have more Pectin than ripe fruit.
Fruits that are high in Pectin include Apples, Blackberries, Cape Gooseberries, Crab Apples, Cranberries, Gooseberries, Grapes, Medlars, Plums and Quince. Any citrus fruit peel is also very high in Pectin. Sometimes you will see recipes combining ripe and unripe fruit together. That is done for a reason. Fruit which is just underripe or just ripe contains the highest level of Pectin that the fruit is going to reach; past that, the Pectin levels will decrease. However, the flavour won't be as developed in the unripe fruit: that will come from the fruit that is ripe.
Fruits that are low in Pectin include Apricots, Blueberries, Cherries, Peaches, Pears, Raspberries, Rhubarb and Strawberries.
When dissolved and let cool, Pectin forms invisible strands that hold liquid in. Acid (such as lemon juice) helps draw even more Pectin out of fruit when it is heated. Water is attracted to sugar. Adding sugar causes some water to be drawn to the sugar molecules, leaving the Pectin molecules free to more easily get at and bind with each other, setting the preserve.
Pectin is available to consumers as an "extract" under the brand names of Certo, in North America and the UK, and SureJell in America. Both are made by Kraft. Certo in the UK is made from apple Pectin that comes from apples that were pressed for other purposes, such as juice or cider. The pressed apples are filtered, concentrated, and have preservative added. It comes as a liquid in bottles. In North America, Certo is made from citrus peel (in 2004, Kraft says Lime peel, in fact), and is available as a liquid in bottles and as a powder in boxes. Powdered Pectin contains some type of sugar, such as dextrose or sucrose. The liquid Pectin tends to be used in jellies; the powdered tends to be used in jams and preserves. Apple Pectin is somewhat available in North America, but really only to commercial processors.
Pectin that doesn't have much added sugar will probably still require you to make up for the sugar when you do your recipe, but lower-sugar Pectin does allow for recipes to cater to different types of fruit, as opposed to a high-sugar Pectin that blasts all types of fruit equally with sugar. If you add commercial Pectin to a recipe that didn't originally call for it, you have to use more sugar, often twice as much as originally called for, to give the Pectin something to react with.
Commercial Pectin is expensive. Some people who have access to "free" fruit -- either because they have grown it, or it has been dumped on them by desperate neighbours who can't cope with the bounty of their own garden, or "bargain fruit" when it's available in the fall by the bushels for a song, find that they end up spending way more on Pectin. But for the rest of us, who have to buy our fruit at normal prices, using commercial Pectin can be a no-brainer. It does basically help to guarantee you good jam results, which can be important if you consider how expensive fruit is and how awful it would be if it all went to waste in a preserve that went wrong.
Some people feel that Pectins that are added at the end of the cooking are better, as then no Pectin gets destroyed while the fruit is being boiled.
Powdered is mixed in with the fruit before the fruit is heated. The liquid is added to the fruit after it is cooked.
When you are making a recipe that calls for added pectin, make sure you are using fully-ripe fruit. Unripened fruit has about a quarter more pectin than ripe fruit, and that additional natural pectin along with the pectin you are adding might make the stiffest jam you have ever seen.
To test to see how much Pectin is present in a fruit juice or stewed-down fruit, put 1 tablespoon of rubbing alcohol into a glass, and add 1 tablespoon of juice from the fruit (allow the juice to cool for a minute or two first), and let stand for 2 to 3 minutes. A jelly-like blob should form. If the blob cannot be fished out with a fork, there's not enough pectin present to do anything with. If you can retrieve it with the fork, but it hangs done from the tines, you will get a loose gel. If if mostly stays on top of the tines of the fork in a blob, you will have enough pectin to form a very happy gel. (Obviously, discard this juice when you're done your test -- not that consuming blobby stuff in rubbing alcohol would probably appeal to most people anyway.)
Here's how to make your own Pectin:
1 pound (450g) of sliced crab apples (don't peel, just wash)
1 1/2 cups water (12 oz)
Simmer slowly for 30 to 45 minutes. Strain first through a sieve to get the juice (discard the boiled apple remnant or sweeten it like crazy for an apple sauce). Then filter the juice; either through a drip coffee filter, or through a piece of clean cloth put into a colander.
To use with low Pectin fruits, use 4 to 6 tablespoons per cup of mashed fruit. As well, per cup of mashed fruit, add 3/4 cup to 1 cup of sugar (6 oz to 8 oz / 180g to 225g).
You can freeze this Pectin, or jar it and process in a water bath for 15 minutes for shelf storage.
Fruit pectins stored at home from one season to the next don't seem to perform very well. Generally, you are best to buy fresh pectin for each season. After all the work of making preserves, you don't want it to fail because you tried to cheap out on getting fresh pectin.
Louis Nicolas Vauquelin first noted the ability of some juices to gel, in 1790.
We first understood the actual role of pectin in the 1820s. Henri Braconnot (1780–1855) was the first to identify it clearly in his 1825 paper, "New Observations on pectic acid." (Annales de chimie. 29, 96-102.) He suggested the name "pectic acid", from the Greek word "pextis." He identified what actually happens. Pectase is an enzyme in fruits that converts pectin into pectic acid, causing the coagulation that we see as "setting."
Housewives began using the knowledge of what fruits and what part of the fruits the most pectin was in to make better preserves. Pectin as a separate commercial product was first sold in 1908 in Germany; it was the liquid version.
In 1919 the Douglas Pectin Co. of Fairport, New York, took over a steel / munitions plant in Cobourg, Ontario, and made it the first Pectin plant in the British Empire to manufacture Pectin. For the first 4 years, the Pectin was sold to commercial processors in Canada and the UK; it was put on the retail market for home consumers in 1923 under the brand name of Certo.