Canning feels like equal parts science and magic. Sure, we understand the basic facts of cooking the fruit and sealing it inside jars. But you can’t deny there’s something magical about opening that jar months later and spooning out a taste of summer. Pectin is one of the key players in this magical process. Ever wonder what it's doing?
Pectin is a gelling agent that helps to thicken and solidify the fruit juices. It’s a naturally occurring substance found in the cell walls of plants - in fact, it’s part of what keeps the plant tissue rigid and gives fruits and vegetables their shape. The powdered pectin you find commercially is usually derived from apples.
In canning, pectin is released from the cut fruits during cooking (or additional powdered pectin is added) and a few things have to happen in order to make it gel again. Simmering the fruit evaporates some of the moisture and concentrates the pectin. And then, the adding sugar and an acid like lemon juice encourage the pectin to reform as a jelly.
If your jam ends up loose and liquidy, either you didn’t cook it long enough, didn’t use enough sugar, didn’t use enough acid, or there just wasn’t enough pectin in the fruit to gel it after cooking. If your jam ends up very hard, one of the reverse scenarios probably happened.
The Joy of Cooking has a lot to say about pectin and canning. Its authors are adamantly against the use of commercial pectin because they feel its use require the addition of too much sugar, to the point where you lose the essence of the original fruit. Instead, they recommend supplementing low-pectin fruits (like pears, cherries, and raspberries) with some high-pectin fruits (like apples and plums).
What experiences have you had with pectin while canning?
Related: Daily Preserves: How to Make Apple Pectin Jelly
(Image: Flickr member healthserviceglasses licensed under Creative Commons)
10 Picnic-Ready Salads to Eat Outside
Easy Entertaining Recipe: Grilled Peppadews with Smoked Mozzarella
Good Food to Share 
The Big Book of Small, Cool Spaces 
Apartment Therapy Presents 
The Eight-Step Home Cure 
Red-and-Pink-Stripe...
Must-See Small Cool Homes: Week Two
Juan's Garage Turned Modern Guest House
I use powdered pectin; it'd be nice not to, but when I've made strawberry jam without it, the first time I had a rock, the second time, syrup. It gives me piece of mind, and lots of jars of edible jam, which is better than inedible stuff.
I agree with the Joy of Cooking authors. I prefer much less sugar in my jams, and I never have had trouble with the jams I've made, usually strawberry, apricot, or cherry. I'm sure for something like raspberry, there may not be that much choice.
One of the things I've really been wanting to make are pates de fruit, but you must have pectin to make those (the best kind being the most difficult to find for regular folks like me who don't like to have to order online). These little guys also usually require an ungodly amount of sugar--usually equal to the weight of the fruit!
I have only used pectin once, when making some peach jam. The results weren't bad, but I prefer not to use pectin because I find it jells too much. It's nothing against the product, but I have great food memories of my grandfather's raspberry jam, which was on the looser side.
That being said, I would stick to pectin if I was attempting to make a firmer jam, or if I wanted to take out some extra insurance that the fruit would jell properly.
I almost always use low-sugar pectin in my jams, jellies and preserves. There are a couple of different options such as the Sure-Jell's "Low Sugar" pectin, or Pomona's Universal Pectin which uses a calcium water solution (included in the box) to create the set rather than the sugar/acid reaction needed for other commercial pectins. This allows you to reduce the sugar significantly, or even use honey instead of granulated sugar. Using these products give me peace of mind that my jams will be an appetizing consistency and actually taste like fruit, not sugar.
I use it as infrequently as in as little quantity as possible. It's tantamount to putting flour in your jam. It isn't authentic. Jam is (should be) a delicate candying (temperature) process, which pectin eliminates. Pretty gross stuff.
Up until this year I've always used pectin in jams, I too like the low sugar pectin the best, it gives a more true flavor than the regular stuff. But this spring I went the pectin-less route and used grapefruit juice in with my strawberries. I really liked the result, which was looser than a pectin jam for sure, but not much, and had a fantastic flavor.
This is the recipe I came up with
http://driedfigsandwoodenspools.blogspot.com/2010/05/full-cupboards-and-excitement.html
I also tried a powdered pectin a few weeks ago that is made from ground grapefruit peel. My first try with it turned out perfect, the second time I cooked longer than I should have and had a thicker jam than I wanted, still good, just thicker than I like. Cant remember the name of it though....
I was reading on a canning site recently that the author only uses lemon seeds in tea ball or bouquet as her pectin source in jams and jellies.
I, myself, don't like pectin much. First, it's not traditional - noone 100 years ago was pulling out a box of powdered pectin. It therefore gives me the creeps.
Second, we always called "softer" jams "English Style". Many of my jams end up no better than thick sauces, but we love them all the same. They are perfect over pancakes or ice cream, etc. I don't see a non-firm jam as a failure.