Like so many of these Canning 101 posts, I’m writing this one to address one of the questions I am frequently asked. I’ve covered this topic as part of larger blog posts before, so if you’re a long-time reader, some of this may be familiar. But it felt like time to pull out this question specifically in the hopes of helping people find the information more easily.
So often, people look at one of my recipes and see the volume of sugar it calls for and have something of a heart attack thinking about all those cups. And so, they write in to ask, “can I safely reduce the amount of sugar in this recipe?”
The answer is that you can always safely reduce the amount of sugar in a recipe, because sugar doesn’t make things safe. The only thing that makes a jam, jelly or other sweet preserve safe for canning in a boiling water bath canner is the acid content, because that’s what prevents any potential botulism growth.
However, when you reduce the amount of sugar in a recipe, you can compromise that preserve’s shelf life, yield, and ability to set up.
Sugar is a powerful preservative, because once you have a certain concentration of sugar in a recipe, the sugar sucks up all the available water. Mold and bacteria need water in order to develop, and if there’s no water available, they cannot grow.
This is why preserves with higher amounts of sugar hold their quality longer than lower sugar preserves. As long as you’re okay with a somewhat decreased shelf life and a relatively short lifespan once the jar has been opened, then go ahead and reduce the sugar.
Things get a little trickier when you take set into account. Sugar has the ability to change physical consistency as you heat it. If you’ve ever made candy, you’ve seen how you get different outcomes the higher you allow the temperature of the cooking sugar to go.
When you make a sweet preserve, you boil the fruit and sugar together, cooking out the water and increasing the concentration of sugars (both natural and added) to the point where they can elevate in temperature to around 220 degrees F. That’s the point at which sugar starts to thicken into a gel and is then able to bond with the pectin (again, both the natural pectin in the fruit and any pectin you added) and that’s how your jams and jellies set up.
If you pull out a lot of the added sugar in a recipe that is depending on sugar to achieve set, the chances are good that the finished product may be forever runny (true story. As a kid, I thought all homemade jam was inherently runny, because my mom always reduced the sugar to the point where set could not be achieved).
You can often reduce the sugar a little bit, but if you do, you may need to cook it longer so that the proper concentration can be reached. That reduced sugar and longer cooking can end up reducing the yield by as much as a cup or two.
Now, if you’re working with Pomona’s Pectin or some other low/no sugar pectin, you can ignore everything I’ve said about set and yield, because those pectins use an entirely different paradigm in order to achieve set. But the advice about shelf life will still hold true.
One final word. Do not take this blog post to mean that I am advocating super high sugar preserves. My favorite ratio for basic jam is two parts fruit to one part sugar, which is actually a fairly conservative amount of sugar, when you look at the traditional jam recipe canon.
When I make smaller batches, I drop the sugar to a three parts fruit to one part sugar ratio, because smaller batches lend themselves to more rapid water evaporation and sugar concentration. And I’m currently writing a book about preserving with a half dozen natural sweeteners, so I am more than open to using a wide world of sweeteners. But I feel strongly that people understand why an ingredient is in place before they go and start changing things up.