Overshot mash temp - Bad JuJu?

So I kind of had a bad feeling when I started making the starter for my IPA on Friday. Brewing Saturday was very spastic to say the least, and I am pretty sure there were gremlins in my equipment. My digital probe thermometer went wacky, and did not match up with my other two thermometers (actually all 3 were different, but the probe thermometer was WAY off).

I was shooting for a mash temp of 153º so I preheated the MLT, got the strike water up to 166º, added grains and the temp was about 149-150º. So I had some boiling water ready to go, and added a little (maybe 3-4 cups?), stirred and called it good. 90 minutes later when I took the lid off my MLT, the thermometer inside said 158º!!! So I overshot by 5º. I did a double batch sparge and collected my 7 gal of wort OK, but my efficiency was only 70% and my OG was under what was predicted.

What effect will a 158º, 90 min mash have on my beer? Is the high mash temp the probable cause for my low efficiency?

Sounds like a nice, thick IPA. May not be quite right for the style, but for me, it would be nice balancing all that alcohol and hoppyness with some mouthfeel.

In all reality, since you said you were having issues with your thermal guessing devices, your true mash temp will be different than what you measured. So no worries! It'll likely turn out fine, might even be a competition-winner in the style.

It's hard to tell since you didn't have a good handle on what your temps really were. Higher mash temps mean more alpha amylase activity, and at 158º you're starting to denature the beta enzymes, so you can get more unfermentable sugars and a sweeter/thicker/heavier beer in the end.

Next time, make sure you stir for much longer to let the temps stabilize. I bet your strike temp probably had you really close, and you just took a reading before the temps stabilized.

Lil' Sparky said:

I bet your strike temp probably had you really close, and you just took a reading before the temps stabilized.

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I think you are right about that. The thermometer that I left in the MLT is VERY slow coming up to temp (but drops really fast), and I was in a hurry because I didn't want to let steam/heat out of my MLT. An extra min wouldn't have hurt if it meant I wasn't scorching my grains for an hour and a half.

The OG on this beer was SUPPOSED to be 1.073, but it actually hit 1.062. So now I am expecting this to be a 6% beer instead of a 7%.