Reader Eliza asks if I can say more about how pectin works. Reader Eliza, saying more is my specialty. So let’s get underway.
Pectins are long-chain sugars (carbohydrates, also known as starches) that are found in the walls of plant cells, particularly the walls of fruit cells, where they form a sort of elastic, moisture-retaining barrier that does double duty as a glue that holds the cells together. Occurring in tightly wound bunches, pectins are abundant in the skins of fruits (apples, grapes, berries, peaches, etc.) and are most numerous right before a piece of fruit reaches peak ripeness. Past that point, the pectin molecules being to degrade.
Pectins can be released by cutting up and/or mashing fruit, then heating it. As long as the surrounding environment is sufficiently watery, the pectin molecules will come loose, then disperse. Properly managed, those dispersed pectins will behave not unlike gelatin, which is an animal protein, and of course a handy thickener. However pectins are a little fussier to work with. As they spread out into a jam mixture they pick up negative electrical charges. That causes them to repel each other rather than bond to one another.
The jam maker fixes this problem by adding acid — usually in the form of lemon juice — which neutralizes the negative electrical charges and makes the pectin molecules want to play nice again. They come back together, only this time there’s quite a bit of flowing water between them. As they try to link back together, that water flow is restricted, and thickening is the result.
But there are risks involved in this delicate little molecular dance. Too much acid will damage the pectin molecules, making them un-linkable. Excessive or prolonged heat will flat-out destroy them, breaking up the flow-restricting network and causing a jam to thin out again. This is why, after a certain point, no amount of further cooking will cause a de-thickened jam to gel again. It’s also why, if you heat a mixture with packaged pectin for too long, the jam will still come out runny (though I never complain about a fresh fruit waffle syrup or ice cream topping).
These potential pitfalls make traditional jam-making a bit challenging for the beginner and the experienced cook alike. The process unfolds in four basic steps. First, the mashing of the fruit. Second, the gentle heating to release the pectins. Third, the adding of the acid to bring the pectin gel together. And lastly, the cranking of the heat to a roiling boil, which quickly concentrates the sugar syrup before too much of the pectin network is destroyed.
It all happens rather quickly and can be rather stressful. But the result is worth it: a jam that’s not just indulgently sweet and fruity, but that also glistens like crystal on the spoon. And if the result is a little runnier than a commercial jam, who cares? I’ll take that in a heartbeat over the overly-thickened mass-produced stuff. A jam with too much pectin not only has a duller taste than its looser pectin-light cousin, it has far less eye appeal, being cloudy with starch. Give me a spoonful of that flowing, sparkly fruit jewelry any day.
Is jam the only thing pectin is good for? No, but because it requires both acid and heat to activate — plus it needs to be administered in a fairly high concentration — it’s not as useful as many other commonly available thickeners. And that’s what I have to say about pectin. Thanks Eliza!