This is a discussion on Canning question within the General Prepper and Survival Talk forums, part of the Survivalist, Prepper, Bushcrafter, Forest Rangers category; Originally Posted by hawgrider Yup a gauge will get you in trouble especially if not tested at the beginning of each canning season. And a ...
Using weighted jiggler process times are at 10-psi for elev. < 1000 feet, 15-psi above 1000 feet elev. I can't remember what elev. 15-psi would not be effective/canner to reach 240 oF? It is above 8000 feet
For some high acid foods/pickeled, it may recommend only using 5-psi. But those foods can be safely canned in a water bath canner
Don't trust a gauge unless it's calibrated.
Well if there's a way for me to create a problem, you can bet I'll find it, usually by accident......but you're right that it isn't done in the canning process itself, but not allowing the jars to cool properly afterward.
For the last few years when canning corn, it tasted sour....kinda like pickled, and the only thing I put in those jars was corn and water. I don't even add canning salt. So doing some research to find out why that was happening, I found this about flat sour....
Flat sour is an unappealing off-flavour that canned goods, home or commerical, can develop. It was studied as early as 1937 by a researcher named Barlow: “[Barlow] also described several causes of flat sours and recognized that the flat sour may be caused by more than one organism.” 
It is caused by some microorganisms that survive the canning process. They are referred to as thermophilic (aka “heat loving”). The actual bacteria that cause it can include (depending on the food product) strains of Bacillus stearothermophilus, Bacillus licheniformis, Bacillus coagulans, Bacillus macerans, and Bacillus subtilis. 
They are harmless with regard to food safety, but they cause the food to ferment in a way that produces a sour off-taste and smell without producing any gas. Metal cans will not bulge, nor will lids pop off of jars as there is no gas to cause that.
It is described as sour because of the taste and smell, and flat because it doesn’t produce gas that could bulge or blow the lid
Strangest thing is that I've been canning for around 40 years now and 20 of that in this house....but have only had this problem develop in just the last 5 years and is always with corn.
Seems the flat sour is due to not cooling the canned material, as soon as possible after pressure is down. And thermophillic bacteria are more widespread than I knew about.
I've always removed my jars from the canner soon after processing. Perhaps that is why I've not had the problem?
I've only had the PC for just over a year. Previously I had only waterbath canned, and still had the problem, but my plan for this year is to do my canning in the fall/winter and in the meantime, stuff is going in the freezer until then.