Is this true for all mash temps? The same at 148 as 158?
I have not run enough experiments above 153 F to know for sure. 40 minutes is certainly sufficient from 147 to 152 F. Above that temperature, my preliminary results are that MORE time might be needed to assure decent attenuation, which I would define as greater than about 70%. Perhaps 45 to 50 minutes is needed at higher temperatures, due to denaturing of much of the beta amylase enzymes. Just a hypothesis at the higher temps. But I have been very pleased with a 40 minute mash time from 147 to 152 F. Or perhaps 45 minutes if you want to play it super safe. Experiment and find out for yourselves!!
Very interesting to hear this. And would grist makeup change any of this or would it likely hold true for most modern malts? Sounds like some experiments are in order!