I’ve made a lot of jam in my canning career. Between the years I logged as a kid helping my mom and all the many batches I’ve made as an adult, I’ve stirred and canned enough sweet preserves to fill a generously sized kiddie pool.
One thing I’ve learned in those hours over a canning kettle is that jam making is a lot like life. It’s not always going to be perfect, but you can almost always turn it into something useful and good.
When I teach jam making classes, one point I always emphasize is that you have two choices when you make a sweet preserve and it doesn’t turn out as you intended. You can either stress about it and try to redo it (and even then, you still might not be able to exactly hit your texture target), or you can change your expectations and move on.
I belong firmly to the school of changed expectations. Some days, I have a hell of a time getting my jam to set. As someone who prefers a softer set to start out with, this means that those underset jars are essentially sauce or syrup. So I call them just that. Instead of apologizing for my underset jam, I call these products sauce, or syrup or yogurt topping. I use them to glaze meat and tofu and I whisk them into vinaigrettes.
I’ve also made jams in the past that, once cool, set up into unforgiving blocks of rubbery fruit. They are so firm that they can be convinced to slide out of the jar in a single cylinder. Even in that case, it is still salvageable. You can serve little slices of that overset jam with a plate of cheese and charcuterie and call it a fruit paste (like membrillo). Or, you can cut it into cubes, roll it in granulated sugar and call it pâte de fruit.
These variations in set happen to the best of us and they can happen even with the most reliable recipes. I find that while past experience does inform every jam making session, you have to approach each batch individually.
Some years, fruit contains more water and less sugar. Other years, the opposite is true. On humid days, when a thunder storm is rolling in, the amount of moisture in the air can make it impossible to cook enough water out of the fruit to achieve a good set. The width of your pot can also impact your finished product, as can the power of your stove.
Depending on how the batch you’re making at the moment is behaving, you can adjust heat, cooking time and the quantity of additional pectin in an attempt to compensate. But from year to year, there will always be a natural variation in set, length of cooking and even yield.
My very best advice is to try to learn to adapt, be flexible and exhibit some kindness to yourself, your preserves and the recipe writers who live in the same changeable world that you do.