Overshot Mash Temp then recovered - Whats going to happen?

I read the wiki and searched the forums for the answer to this, but I can't find it anywhere.

Is enzyme deactivation a one way street (permanently deactivated) when you reach a certain temperature? Or can the be reactivated upon lowering to the normal mash range of 150F to 156F?

Also if the mash temperature is overshot are the sugars going to be a type that are unfermentable that can not later me converted by lowering the mash temp?

The reason I ask is I normally hit my mash temp, but I stirred my grain longer than I normally do and my temp dropped 3F. I turned my burner on low, stirred longer and hit my mash temp of 154F. Put the lid on and oops forgot to turn off the burner.

15 minutes later I realized the burner was on (clicking of oven thermostat) and turned it off. It was at 165F and I brought the temp back down quickly with ice. Then I left it at 150F for the rest of the time.

So what is likely to happen. The last time I brewed this beer I ended up with 1.008 and I hit my mash temp fine and left it alone.

Will the high mash temp cause the sugars to be the wrong type to ferment? Or will recovering the mash temp to 150F make everything ok?

When enzymes are denatured, they'll never come back. But, they're not instantly denatured at higher temps.

But, something interesting to keep in mind. In thin mashes, enzymes are rapidly destroyed above 149*. In a thick mash, beta-amylase is destroyed in less than an hour about 149*, and alpha-amylase is destroyed within two hours about 154*, but you can't get a very dextrinous wort below 153*.

So, the enzymes in question are denatured at "normal" mash temps.

As long as you checked your pH and did a starch conversion test, I'd say your beer will be fine, but maybe a little more dextrinous than last time.

Well the beer attenuated maybe too much to 1.009, which may be a little low for a mild with an OG of 1.040. It tastes thinner than the last 2 batches of mild. I attribute that to going too low to 150F with the mash temp after going to 165F. I think this caused me to wind up with too much fermentable sugar.

If I put some simple syrup in the glass after I pour (just a dab to bring it up a few gravity points) it tastes awesome, just like the other 2 batches I made of JZ's mild.

What I think I will do is add some Lactose (unfermentable sugar) to bring the gravity up a few points and hopefully that does the same as what the dab of simple syrup did in my glass.

I can't believe I managed to screw up such a simple beer. I'm happy my mistake is recoverable though and quite yummy after a little help.