Gregor Thanks for the clarification on pasteurization vs sterilization and the times associated with them. I've been running my blocks for 90 minutes since conducting this test and haven't had any growth on blocks, even ones that sat for several weeks before inoculating.  

David Medlock This is the probe I used. https://www.tappecue.com/airprobe

David Medlock I'm in salt lake city.... 5000ft so water def. boils at a slightly lower temperature here. 

Gregor  It's been a little bit since i posted this question, but I figured a way to track the inner temp of a substrate block inside a pressure cooker by utilizing a wireless bbq thermometer made by tappecue. It's a little super capacitor powered rod like thermometer that's small enough to fit in the bag and measures both the inner temp of the bag (probe 1a) and the inside temp of the pot's chamber (probe 1b). The bluetooth punches right through the steel / aluminum presto pressure cooker to their data logger app. 

My results seem to indicate I only have to run for 90 minutes once my pressure cooker gets to 246F temp and 15 PSI (PSI isn't shown on this graph, I visually tracked the 15 PSI once it hit 246F).   Running for 90 minutes at 246F / 15 PSI gets the inner temp of my 6lb masters mix block to 212 degrees for 1 hour. Would my blocks be considered sterile at this point? 

SwainI jam 4 x 6lb blocks of masters mix @ 60% hydration in a unicorn 14A bag into a presto 23 and haven't had any issues with contamination at 2.5~3hrs. They can sit on my shelf for a couple weeks without any issue. I do get a blown out bag every 200 or 300 bags when packing them in so tightly but it's not that big a deal to for me to lose at that loss level. 

Thank you! I think I needed confirmation that this data didn't exist and/or was extremely difficult to find. It seems like everyone has just accepted the 2~3hrs time as the standard. I'm a bit data driven so it got my mind working and I figured a way to measure the temps over time inside the pressure cooker. I'll graph out my results and share here.