Fill a bowl with cold water and 1/4 cup of lemon juice (or 2 tsp of citric acid). Set up your workstation with a peeler, cutting board, sharp knife, and a bowl for the peels and cores.
Clean your apples, and peel, core, and slice the apples thinly.
Once you have a bunch of slices soaking, combine water and sugar (optional) and bring to a low boil.
Cook the apple slices in batches in the hot syrup, and boil for 2 minutes, stirring constantly.
Transfer the cooked apples into your hot and sterile canning jars. Pro tip: I found that tongs worked the best for this.
Cover the apples with some of the hot water or syrup, allowing for 1/2 inch of headspace.
Use a wet clean rag and wipe the rim of the jars to make sure it is free of any food.
Place a clean lid on the jar and tighten the ring to fingertip tight.
Once the water is boiling, gently place your jars in one at a time using tongs. Once your jars are completely covered with the boiling water, put the lid on and boil for 20 minutes (pints or quarts).
When the time is up, turn off the stove and let the jars sit for 5 minutes in the canner and then lift them out with canning tongs. Place on a towel where they can sit undisturbed for 12 hours.
After a few hours, to check for sealing, gently press down in the middle of the lid. If the lid has no give, it’s sealed. If you can press the lid in and it pops a bit, your jars are not sealed. You can reprocess them or store them in the fridge or freezer (only freeze jars that are wide mouth).
Headspace is defined as the space between the top of the food and the top of the jar. You’ll need about 21 pounds of apples for canning 7 quarts of apple pie filling.This canned pie filling can be frozen in wide-mouth canning jars. Leave 1.5 inches of headspace in the jars to allow for expansion during freezer. Allow to fully cool in the jar before freezing.