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Due to time constraints, I need to do a two- to 2-1/2 hour unattended mash, and then return to lauter, etc. I plan to do a single batch sparge. I am looking for a slightly-less fermentable wort for more body, so I theorize that my ideal mash profile is a single-temperature rest at around 156-158°F (69-70°C). However, my non-heated mash tun is going to lose around 15°F (8.3°C) over 2-2.5 hrs., I estimate**. So I need to mash in higher. I don't have the ability to add more strike water mid-mash because I am maxed out on MLT space, and will not be around to do it.

Q1: What sort of wort profile can I expect if I mash-in at 162°F (72°C) , and end up at 147°F (64°C) over 2-2.5 hrs.? John Palmer says in How to Brew that beta-amylase is denatured at 154-162°F (68-72°C), but I have seen other writers say that overnight mashes lead to very fermentable worts and dry beers.

Q2: Does the mash-in temp determine the fermentability of the wort, or is it based on the whole mash?

Q3: Besides buying a new cooler, do you have any advice in terms of tips, techniques, or mashing temps?

In case it matters, this is a partial-mash recipe; 2.5 gallon (9.5 L) batch (fermenter volume). My malt bill is 4.2 lbs. (1.9 kg) of grain (71% Golden Promise, and 23% Belgian Caramunich, 8% 160°L crystal), mashed at 1-1/3 qts./lb (0.57 L/kg), plus 0.75 lbs. (0.34 kg) of DME. Yeast: Danstar Nottingham.

  • ** My two-gallon (7.6 L) beverage cooler mash tun loses 10°F (5.6°C) in one hour without a blanket, but I have added insulation to the lid and plan to wrap in a blanket, so I expect a maximum 15°F (8.3°C) loss over 2-2.5 hrs. I do preheat the cooler with 185°F (85°C) water. The lack of thermal mass, and inefficiency of cold beverage coolers to keep contents hot, are drawbacks of small batch brewing. This is the first time I am trying for a less-fermentable wort.
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You are putting a pound of crystal malt into a half-batch partial mash beer, and you're trying to mash for more body? This is a bizarrely complicated recipe and process to yield 2.5gal of sticky sweet beer. By all means, brew what you like, but perhaps consider postponing the brew day until you have time to mash properly, and maybe even reconsider the recipe. –  Graham Dec 17 '13 at 20:37
    
Thanks for that advice. I made up the recipe in the grain room at the LHBS, trying to counter super-high attenuation I have been experiencing (yes I tried storing a bottle warm to check for infection). I have an idea of what I want to achieve, but not sure how to get there. I might have to re-design it. Or try it as a learning experience. At least it's a small batch. I'll report how it goes. –  Chino Brews Dec 17 '13 at 21:54
    
@Graham Well, I brewed it last night. Deleted the dark crystal, and bumped up hops slightly. Mashed in at 156°F and it declined to 146°F over two hours. Hit my targets except for evaporation, so topped off. 1.056 OG. We'll see where it ends up. Hopefully not cloying. Thanks for the help. –  Chino Brews Dec 18 '13 at 16:34
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2 Answers

up vote 2 down vote accepted
  1. Denaturing any enzymes takes some time...at least 20 min. If you don't go over 162, you should be OK in terms of having enough beta left. The majority of the conversion will be done in the first half hour or so, but as long as you're still in the 145+ range, long chain dextrins will continue to be broken down into shorter ones.

  2. It's based on the entire mash time

  3. You can wrap your cooler in more blankets or a sleeping bag to help hold the temp.

Between the CaraMunich and the crystal, you have over 30% crystal malt in there. The DME will also add some unfermentables. I don't think you'll have to worry about having a thin beer, even with the overnight mash schedule.

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One question: reference tables say that Belgian CaraMunich and Crystalmalt both have a potential PPG of 33, compared to 37 Golden Promise (and for American 2-Row Pale Malt). Does 4 PPG make that big of a difference in body/malt structure, or is the 37 PPG of base malt more convertible than the 33 PPG of crystal? –  Chino Brews Dec 17 '13 at 21:26
    
Also, I failed to mention that the 160°L crystal is a late mash addition (per the LHBS manager's recommendation) -- I will make that a separate question. –  Chino Brews Dec 17 '13 at 21:45
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It's not the ppg, it';s how the malt is made. Both CaraMunich and crystal are essentially mashed in the husk before being kilned. That means that each has an amount of unfermentables in it. You are correct in that base malts are more fermentable. –  Denny Conn Dec 18 '13 at 16:16
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As Denny noted, there's already a lot of unfermentables. I would start at 154°F since the fermentability of this wort is not going to be high so you want to get as much out of the beta conversion as possible. 160°F is the limit for beta amylase activity and it's quickly denatured.

If you want a thicker body on the beer, try using a less attenuative yeast, such as WLP002, or WLP004.

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WY1450 is great for leaving a lot of silky body on a beer. –  Denny Conn Dec 17 '13 at 19:31
    
And no one better qualified to say so! :) –  mdma Dec 17 '13 at 19:36
    
+1 for the useful info, @mdma. Thanks. I accepted denny's answer only because it addressed the questions more directly. I haven't used liquid yeast yet, but ought to consider it, especially because I can probably pitch it directly into a 2.5 gallon batch without a starter. –  Chino Brews Dec 17 '13 at 21:49
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