I was processing venison in 14 pint jars at 10 lb. pressure. It had only begun to process, approx. 10 min. I got an emergency phone call from my Mother and had to turn off the pressure cooker. I left and did not get back for 5 hrs. By that time the cooker was barely warm. I turned the stove back on and began processing all over at 10 lb. pressure but left it go for 90 min. instead of the 75 min. for pints. All sealed, looks great, good color. However, would sitting and cooling down before the 2nd processing cause add'l bacteria to grow in the sitting jars? Or, would the 240+ degrees from the pressure cooker take care of any and all bacteria, whether a little or a lot? I have been canning and putting up foods for 51 years and have never had to stop and restart processing. I'm unsure if the meat would be safe. Anyone else ever have this happen to a low-acid food?
I would not keep it or eat it and just consider it a loss. That is a long time for the food to cool down/seal, etc. The processing time is usually carefully calculated so that the core of the product in the jar gets to the proper temp. With the processing time only being 10 mins it would mean only the jar and maybe a small amount on the edges would have gotten to 240 deg F.
I suppose it could make a difference if it was a hot pack vs. cold pack, but I would still not risk it.
Since you're an experienced canner, I assume you already know that it's possible to lose pressure during the process and then restart the time when the canner gets back up to pressure, but that is usually a few minutes at most, not hours.