Local fruit, picked at peak condition and turned quickly into jams and jellies, offers an opportunity to experience the pleasures of "making your own." It's not just the act of capturing the flavors of summer that's appealing. Working with pectin has its own rewards, as anyone who has ever witnessed this fascinating substance transform hot fruit syrups into delicate gels could attest.

Pectin is a carbohydrate found mostly in the skin and core of raw fruit. In nature, it functions as the structural "cement" that helps hold cell walls together. In solution, pectin has the ability to form a mesh that traps liquid, sets as it cools, and, in the case of jam, cradles suspended pieces of fruit.

Pectin needs partners, namely acid and sugar, to do the job of gelling properly. Acid helps extract pectin from fruit during gentle simmering and helps the gelling process, which will not take place unless the mixture is fairly acidic. If fruits (such as apricots) aren't sufficiently tart, a recipe will call for added lemon juice.

Sugar enhances the strength of the gel by attracting some of the water away from the pectin. In the absence of sufficient water, pectin molecules are more likely to unite with each other. Sugar also acts as a preservative, firms the structure of the fruit, and helps the jam or jelly hold its color and flavor.

If you're using commercial pectin, remember that each jam or jelly recipe is designed to maintain the correct balance between pectin, acid, and sugar for the fruit you're using. If you mess with the proportions, don't expect jam or jelly to set properly.

Pectin content varies according to the type of fruit and its ripeness. Some fruits, such as apples, blackberries, grapes, and quince, are rich in natural pectin and therefore have an abundance of setting power.

Fruits low in pectin are often combined with those high in pectin. Orange (high pectin) and rhubarb jam (low pectin) for instance, blends two fruits with quite different pectin contents. Or commercially packaged pectin can be added to fruits low in natural pectin, like apricots, rhubarb, and strawberries.

Note that just-ripe fruit contains the highest pectin levels. When fruit ripens further, its pectin content decreases as pectin turns to pectic acid. Don't be overly impressed by advertisements for "jam berries" that imply that overripe mushy fruit is optimal for preserving. Though in very ripe fruit, flavors are fully developed, pectin is often past its prime. For best results, mix fully ripe fruit, which has the best flavor, with just-ripe fruit, which has the highest gelling power.

Give jam and jelly making a try this season. You'll not only enjoy the process, but come winter, you'll treasure your results!