Effect of Long, High, Decling-Temperature Mash on Wort

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.

Topic small-batch partial-mash wort mash homebrew

Category Mac

1
answered at

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.

1
answered at

  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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