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With an automated mash setup, it could be fairly easy to bring the mash to a boil and cool it. I'm wondering if this could be used to replicate the results of a decoction.

If mash thickness is important to the desired effect, you could pump a fairly precise amount of the wort out of your mash to thicken it before you boil.

A plate chiller or similar could be used to cool the mash, allowing you to achieve different rests like a traditional decoction.

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up vote 6 down vote accepted

No, you really don't want to boil the entire mash--that would denature all the enzymes! You'd end up with a very starchy beer.

With a traditional decoction mash, you typically wait 15 minutes, then pull 1/3 of the mash (a thick pull: mainly grain plus a little wort) to be boiled. The reason behind this: what's pulled contains relatively little enzymes, the assumption being that they have been dissolved from the grain into the liquid. As such, boiling the grains does little to reduce the total diastatic power of the mash.

If you boil the whole mash, you'll destroy all the enzymes, leaving you with only a partial conversion--a lot of starch and little fermentable sugars.

Once you've boiled the whole mash, there's no point trying to cool this to do any rests--all the enzymes that perform beta glucan, protein, and saccharification rests are long gone. Furthermore, the rests in a decoction are the same as any other method of raising the temperature in a mash (infusion/direct heat). However, historically decoction was effective in the absence of accurate thermometers, since it allowed the brewer to hit rest temperatures by measuring the volume of the decoction rather than by directly measuring overall temperature.

If you wanted to experiment--and I stress experiment!--then you could boil the mash after the normal mash is complete. This may increase the quantity of melanoidins. If you try that, please post your results!

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Good point. You could boil at the end of the mash (after any steps you wanted to do)... –  stephelton Jun 27 '13 at 20:55
    
You were quick off the mark - I added a paragraph about that shortly after submitting the answer! (Before I saw your comment.) –  mdma Jun 27 '13 at 20:56
    
Funny. Nice setup, by the way. I'm giving this serious consideration only because I'm designing an electric system (with similar influences as yours) and wondered if there might be enough advantage to putting a heating element in the mash tun to justify doing so. –  stephelton Jun 27 '13 at 20:59
    
Thanks, I'm happy with the setup! Regarding your setup, I wouldn't put an element in the mash - cleaning a regular element is hard enough, let alone one covered in grain particles. Plus, you don't want to be scorching the mash. Decoction mashes have fallen out of favor, some brewers - e.g. Denny Conn - have reported no difference in flavor, or what difference there is can be approximated by melanoidin malt. Try first without - you can always add an element in later if you really want to. –  mdma Jun 27 '13 at 21:09
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It's not just me. In experiments I've done with blind triangle tasting, a majority of tasters either had no preference or a preference for non decocted beers over those that were decocted. ahaconference.org/wp-content/uploads/presentations/2008/… , starting on pg. 25 –  Denny Conn Jul 2 '13 at 18:12
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