[gymrat]

1. What does it do?
2. How do you perform it?
3. Is it necessary?

[jamminbrew]

1.  Mash out basically stops the enzymatic activity, stops the conversion of starches in the grain to fermentable sugars.
2. Raising the temp of the mash to approx. 168* and holding for 10-15 mins.
3. Debatable, I have and I have forgotten, and noticed no difference.

[dannyjed]

I did it my first 5-6 all grain batches and with the advice from some on this forum I found it not necessary.  Some have stated that a mash out helps boost efficiency and I don't believe it since it stops conversion.

[tubercle]

1. Don't know
2. Don't know
3. Don't know

Tubercle suggest:

1. Mash
2. Sparge
3. Enjoy

[tygo]

Boost the temp up to around 170F and hold it there a good long while, say 20 minutes.   It should denature the majority of the enzymes and lock in the fermentation profile.  Many people think it's not necessary but like many other things in brewing it all depends on your system.

My wort tends to sit in the kettle for awhile during the runoff at 140-150F so if I'm trying to achieve the effects of a mash temp at 150+ I will usually do a mashout prior to starting the runoff.  If I'm brewing up a Belgian Strong Golden ale and mashing at 148 anyway then I don't bother. 

[jgl2ltts]

Mashing out supposedly increases efficiency by solubilizing more fermentable sugar in the grain than would be extracted at the lower mash temperature.

My experience is consistent with the previous respondent, I've forgotten to mash out and found no difference in the final outcomes.  Perhaps it's more significant when mashing larger volumes of wort (I generally do 10 gallon batches).

[dannyjed]

I agree that to do or not to do a mash out depends on your set up and equipment.  I don't and I'm happier that I have one less thing to forget

[tom]

I agree that "it depends".
I believe that the increased temperature doesn't lock in the fermentability profile.  Alpha amylase works well into the upper 160's and it takes longer than 20 minutes to denature it.  I do it because I can (direct-fired RIMS) and I think I get a little bit more efficiency and clearer beer.  Neither are scientifically proven though, nor terribly important.  I am trying to make my brewing process consistent for now.

[mabrungard]

I also use a RIMS and its easy to set my heater controller to ramp the mash temp up.  I consistently measure several points Brix increase in the wort gravity with the mashout heating and recirculation.  Since its not a big deal for my system, I always do it.

[ccarlson]

1. It denatures the enzymes and thins the sugars. Your efficiency will increase a little and it helps prevent stuck sparges.

2. I add boiling water.

3. Not absolutely necessary, but I think it's worth the effort.

[Kirk]

If you're shooting for a final gravity target higher than all out conversion, then it's important. Because if you don't denature the enzymes, especially beta, then there's a good chance you will still be converting while you're sparging, and you're FG will be lower than you were shooting for.

[nyakavt]

I also use a RIMS and its easy to set my heater controller to ramp the mash temp up.  I consistently measure several points Brix increase in the wort gravity with the mashout heating and recirculation.  Since its not a big deal for my system, I always do it.

This has been my experience as well.  There have been two or so batches where there was no difference in mash gravity (out of 20 sampled) before and after mashout, but most of them have showed a 1-2 brix increase after mashout. 

What I really want to know is if this same conversion happens as the wort in the kettle is heated to a boil?  Although the same thing would be happening the the enzymes as the temperature is raised, the starches that would be solubilized by the higher temp are still, presumably, in the MT, and therefore not exposed to the enzymes for conversion.

[tschmidlin]

I also use a RIMS and its easy to set my heater controller to ramp the mash temp up.  I consistently measure several points Brix increase in the wort gravity with the mashout heating and recirculation.  Since its not a big deal for my system, I always do it.

If you ever feel like testing it Martin, I would love to see what happens on your system if you just did the recirculation while keeping the temperature the same.

[ccarlson]

I also use a RIMS and its easy to set my heater controller to ramp the mash temp up.  I consistently measure several points Brix increase in the wort gravity with the mashout heating and recirculation.  Since its not a big deal for my system, I always do it.

That's about what I see as well.

[SpanishCastleAle]

Can we dispel the myth that mashing out @ 168* F stops all enzymatic activity in this thread?  AFAIK, mashing out denatures the beta amylase (which affects the fermentability) but the alpha amylase (reducing starch to long-chained sugars and long-chained sugars to shorter ones) is still chugging along @ 168* F.  So imo it's correct to say it 'locks in the fermentability' but not correct to say it 'stops all enzyme activity' or 'stops conversion'.

From Kaiser's Theory of Mashing article:

Beta amylase produces Maltose, the main wort sugar, by splitting 2 glucose molecules from the non-reducing end of a glucose chain. It is therefore able to completely convert Amylose. But since it cannot get past the branch joins, Amylopectin cannot completely be converted by beta amylase. The optimal pH range for beta amylase between 5.4 and 5.6 and the optimal temperature range is between 140ºF (60ºC) and 150ºF (65ºC). Above 160ºF (70ºC) beta amylase is quickly deactivated [Narziss, 2005].

Alpha Amylase is able to split 1-4 links within glucose chains. By doing so, it exposes additional non-reducing ends for the beta amylase. This allows for the further conversion of Amylopectin. The optimal pH range is between 5.6 and 5.8 and the optimal temperature range is between 162ºF (72ºC) and 167ºF (75ºC). Above 176ºF (80ºC) alpha amylase is quickly deactivated [Narziss, 2005]