With canning, you're always learning. This summer, I was the student and pectin was the teacher.
It all started when I learned from three different sources (all very reliable) that you should use slightly under-ripe fruit for jam and jelly making. Slightly under-ripe fruit has higher pectin levels than fruit at its peak or over-ripe. For years, I had sought perfectly ripe fruit, and wasn't opposed to using fruit that was slightly dinged here and there -- I'd just cut those bruised pieces out. I think the "dinged fruit is fine fruit" theory was widespread -- even farmers would set aside these slightly imperfect fruits just for home canners at the farmers markets and charge a few cents less. You're going to cut it up, pour a bunch of sugar on it and cook the heck out of it, so it doesn't need it to be perfect, right? WRONG!
I decided to conduct an experiment. I sliced and diced 5 cups of slightly under-ripe plums with the skin on (there's plenty of pectin in fruit skins, seeds and pits) and made my jam according to a Ball Blue Book recipe. The jam did its normal thing, but it seemed to set up faster -- took me by surprise! Before I knew it, my jam was sitting up straight on a spoon. When I opened my tester jar the next morning to have a taste, the knife didn't move through the jam as easily as I like it to. This jam was tasty and tart, but definitely FIRM! (I prefer a softer set, but have friends and family who like firm jam.) I still had loads of slightly under-ripe plums, so for the next batch, I peeled about half of the plums. The result was a nicely set up, but not too firm, batch of plum jam. My theory: If I was going to use fruit that had a higher level of pectin, I needed to remove some of the peel to get the texture I prefer.
One of my sources at the UC Davis Department of Plant Sciences, Diane Beckles, pointed out that canners might have to make a trade-off between pectin content and sugar levels. Slightly under-ripe fruit may not be as sweet -- it depends on the fruit.
There is a lot to consider when you're choosing your fruit! And, now it makes sense when I see tips that suggest using 3/4 firm-ripe and 1/4 under-ripe fruit in your recipes. (Not that you always have a choice when in comes to ratios of firm-ripe and under-ripe. This seems like splitting hairs, even to me.) I'll continue to mix it up and document the results, and of course, share with all of you!
The more you can, the more you can can.
I started The Hot Ping a few years ago and took a break for a bit, but people have said they liked it, dare I say missed it, so I am re-posting a few of my previous Pings. And I hope to keep posting about home canning... it truly is a never-ending adventure.