This isn't a new idea and there are several threads where it's been discussed.
I think the general consensus is that you might "get away with it" but it's far from best practice.
Even if you mashed out at 80
oC there are still lots of bacteria that are going to survive and Alpha and Beta aren't the only enzymes involved in mashing. If you don't get the wort up to boiling you can't be certain that either all the enzyme reactions have been halted or that the wort is sterile.
This idea doesn't make sense from either a theoretical or practical perspective and the economics of it suck, you lose all the heat you payed for, then pay to reheat the wort, which will take something like a quarter to half an hour, that's added to your brewing time not taken away from it.
A Pasteurisation Unit (PU) is the amount of heat required to kill half of the bacteria in 1 minute, at Pasteurising temperatures (at 60
oC you get about 1PU/Minute) as the temperature goes up the number of PU's/M goes up exponentially. Here's a good intro
View attachment 37949 Or if you want to plot the graph in excel PU/M=0.000000003*2.71828182845904^(0.329*t) (t=
oC)
Unfortunately some bacteria are much more heat tolerant than others, good examples of them are the ones that have survived the malting and kilning of the grain we use to male our beer so we have selected for heat tolerant bugs.
If you're going to brew boil your wort.
MHB