Canning 101 - Waterbath Canning for Beginners
If there's any discoloration at the top of the jar, prior to unsealing, you can decide if you want to just toss the entire jar's contents or scrape off the miscolored top and heat the contents above boiling for 10 minutes.
I've made some darned good dishes with canned goods that were questionable to eat as I'd originally intended. Various last jars of chutneys have ended up on bbq sauces, applesauce turned to apple butter, and jams added to fruit in pies.
If you go to open a jar, even without discoloration, and the lid isn't sealed, heat the contents (as above) or discard.
Also, if it smells funny or off, don't eat it. The nose knows.
What happens if a jar breaks in the canner?
First of all, it's glass. Even the most seasoned (hah!) canner has a jar break every now and then.
Here's what you do: Carefully remove and rinse any intact jars.
Using a drain catch (so you're not getting glass down the drain) filter out the broken glass from the water murky with the contents of the broken jar.
Rinse the canning pot and refill with water.
Replace the unbroken jars and reprocess for the entire amount specified in the recipe.
What happens if a jar doesn't seal?
If a jar doesn't seal, I simply re-process it.
I usually leave my canning pot with its water on the stove until I've tested all my jars for their seal. I reboil the water, put the jar back in with a new lid or seal, and reprocess the jar for the time specified in the recipe.
I've even found jars of food unsealed after a month or two and simply followed the above instructions with a new lid and then remarked them with the new processing date.
These are my basic steps for Canning 101. If anyone would be interested in a video class or even a live workshop, let me know.
As the classic saying goes, I eat local all year because I can!