I made applebutter in the slow cooker this weekend. While it was still hot I put it into sterilized jars, put on lids and rings. As it cooled the center of the lid went down (vacumm seal?) My question is are these jars sealed or should I keep them in the fridge or freezer? My grandmother made applebutter when I was a child, hers was so so good.
When I made my apple butter I made sure to process it in a boiling water bath (BWB)
I would reprocess the apple butter, add a little lemon juice, use a new lid, and put it in a BWB according to your elevation (which appears to be below 1k feet so it would be 10 min)
If you think you will eat them soon enough the fridge would be fine. I am not familiar with its ability to be frozen but seeing as it is really close to apple sauce I would think you would be fine. Make sure you have freezer safe jars!
Although the center of the lid went down, this kind of open kettle canning doesn't create a strong vacuum; there is still unexpelled air in the jar. It's also possible without heat processing that certain bacteria (spoilage agents) will survive in the apple butter.
There's no particular health risk with what you did; apple butter is an acid product. But you risk wasting a lot of your hard work because the shelf life is reduced and the possibility of molds, etc. is higher. It's not fun to open a jar and smell mold.
Apple butter is what in the UK would be referred to as a type of fruit cheese, though slightly less dense.
It's apple puree cooked down slowly with sugar and spices. Recipes vary widely.
For my recipe I use 2:1 apple puree to sugar (combining Caster and Demerara). Sugar is sometimes reduced depending upon sweetness of apples.
Spices I use are 4:2:1:1 cinnamon, mace, allspice, cloves. I use far less than many recipes. With long cooking the flavor intensifies and large amounts of spices can turn bitter. For 14 cups of puree I use as little as 1 teaspoon cinnamon and other spices in proportion.
I begin cooking on the stovetop and finish in the oven so as not to worry about spattering. For a more intense flavor and to prevent initial sticking I add a little cider or boiled cider.
When it's done the color will be dark and the puree can be mounded on a spoon with no liquid running out around the edges.
Apple butter is a wonderful accompaniment to pancakes or crepes.
I have a recipe for applesauce bread. It calls for not only the applesauce but apple concentrate. Since I roast my applesauce on low for so many hours, (untimed) Just until it is the consistency I want, it is pretty thick. I replace the applesauce with the butter and then I use applebutter with water mixed to replace the concentrate. Lol, I'm sorry, no specific measurements. Just "by guess and by golly" as my grandpa used to say. And let me tell you, if he were alive today he would be pretty darned old, so you have probably never heard that saying.