Highbush cranberries and apples are both naturally high acid foods on their own and, even without the lemon juice, will not harbor harmful bacteria. It is possible, though, that the lemon in this recipe was included to increase the acidity further, to allow the processing time to be 15 minutes, instead of a longer time. So the risk in excluding the lemon is that some spoilage microorganisms (yeasts or molds) might have survived the heat treatment.
But again, the risk is that your cran-apple butter will spoil (ferment or mold) on the shelf, but not that it will harbor harmful bacteria.
So Iʼd say: donʼt give these jars as gifts, keep them at the front of your pantry, check them for spoilage (fermentation smell or visible mold) when you open each, and use them soon. Alternatively, if you have just a few jars, you could refrigerate them and, again, use them soon.
Thank you Sarah! That is the recipe I use, so I processed for 15 minutes. Just curious though—I’ve made blackberry jam with my daughter in Washington and the only ingredients are the berries and sugar and processing time is 15 minutes. Those berries don’t seem as acidic as the high bush but they don’t call for citrus, and that recipe is from the Ball Blue Book. So if the processing time is the same, wouldn’t it be safe to keep as is? I completely trust what you’re telling me, just wondering
There are several factors that determine the processing time for different sweet spreads. Three of those are 1) the acidity of the original ingredients, 2) the density of the product, and 3) the chemical "reactions" between acid, sugar, and pectin. Because apples, cranberries and blackberries are all high acid foods, factor 1 is not likely the issue. The lemon added to the cran-apple butter might address either 2) the variability in thickness (density) that people reach when making butters, making sure that the acidity is high enough to prohibit yeast/mold growth even if the product is very dense, or 3) the need for extra acid to activate the natural pectins in the berries and apples. Both of those factors may be less of a concern with the blackberry jam. Not having the chemical facts about the two products in front of me, thatʼs just conjecture... the lemon could also just be there for flavor!
An important thing to remember, though, is that (unless you or someone who might eat your cran-apple butter has an allergy to yeast or mold) under-processing your cran-apple butter will not make it unsafe to eat. Under-processing a high-acid food will just leave it at risk of spoiling on the shelf. Thatʼs why I recommended eating those possibly under-processed jars sooner rather than later.
This work is supported in part by New Technologies for Ag Extension grant no. 2020-41595-30123 from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.