I do this every year and the brown stuff has never happened before. I did not waterbath them (never have). I did the upside-down method due to the acid in the berries.
— Question asked by special
You have to be very precise when using this method of canning — the jars and jam both have to be as hot as you can get them (and the jars must be perfectly sterile) otherwise you run the risk of a failed seal. Additionally, the inversion method of sealing doesn't always force out all the oxygen in the headspace. Mold spores live in the air and so if oxygen remains in the headspace of the jar, chances are that the mold will then grow in your jars.
In order to give yourself increased peace of mind, I'd recommend that you consider a brief boiling water bath for your next batch of jam. That's the only way to be certain that you've killed any mold or bacteria remaining in the jars and that you get the optimum seal.
Marisa McClellan, our guest expert this week, is answering your questions on canning and preserving. Marisa writes Food In Jars, a blog devoted to canning, preserving, and other food in jars. She also teaches canning workshops.
Previous Question for Marisa:
• Is It Safe to Can Meat Sauces?
(Image: Dana Velden)