Originally Posted by mux
I have done this twice now-!and not sure if it effects conversion or not. Iodine test confirms conversion but efficiency is low.
Missed mash temp, so I draw off a portion (not all) of strike water from mash tun. I heat it to 200-210 and replace to bring temp up. Is this denaturing the enzymes I need for starch conversation? Any ideas?
Yes, you are denaturing the enzymes in the liquid you're drawing off. However, there are enough left to get the job done. You are not, as has been suggested doing a decotion. A decoction boils mostly grains leaving as much of the mash liquid behind in the tun as possible. That's one of the reasons a decoction increases efficiency as the boil helps break down particles in the grain and leaves the majority of the enzymes behind and untouched by the boil.
If you are consistently missing your mash temps then you should think about raising either the temperature or quantity of your strike water. You could also consider an additional infusion with a smaller amount of boiling water to bump up a low temp.