I recently got a pressure canner (yay!). So far I've only done stock for soup. I want to can some spaghetti sauce with meat, but when I look at the recipes in my canning books and online, they all start with 30 lbs of fresh tomatoes. In fact, they all seem to be identical to or VERY similar derivatives of the recipe from the USDA Complete Guide to Home Canning.
I'm in Missouri. I am very unlikely to find fresh tomatoes in February, especially not 30 lbs of them. I'm OK with using canned tomatoes, but I haven't the foggiest idea how much to use. The tomatoes in this recipe are crushed, cooked down and then strained within an inch of their lives, so I expect there is a lot of loss, but how much? The recipe only calls for 2.5 lbs of ground beef, so it's got to be way less than 30 lbs the make it through the process.
I can guess how much canned tomato to use, but it will certainly vary somewhat from the approved recipe.
I understand that in pressure canning the goal is to penetrate every particle of food in the jar to the magical 240 degrees for long enough to kill botulism bugs. So then isn't the limiting factor the densest food in your recipe?
I also see a recipe for canning ground meat in the USDA book. The recipe for spaghetti sauce requires a processing time of 70 minutes, the ground meat alone requires 90 minutes. Whole tomatoes in juice only need 25 minutes in a pressure canner (all at 10 lbs pressure).
So if the ground meat is the densest ingredient in my sauce, and my sauce will definitely be less dense than canned ground meat, then shouldn't I be safe if I process a sauce derived from these recipes for 90 minutes?
Am I missing something crucial?