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Old 05-21-2009, 02:02 AM   #1
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Default Acid Rests

I was re-reading Horst Dornbusch's book called Bavarian Helles and, while I disagree with some of his recommendations (e.g., blanketly doing a 122°F protein rest on all Helles), I found something intriguing in the Appendices for acid rests.

He states that many German Brewers do acid rests (100°F +/- 5°F or 38°C +/- 3°C), even if mash acidity is not a problem. Here are the reasons aside from pH reduction:

-"allows water-soluble grain substances as well as enzymes to begin to hydrolize, which improves the efficiency of enzymatic conversion at subsequent temperature ranges"

-"activation of beta glucanase... breaks down highly viscous, water soluble gums" which, in turn:

..........-"improves extract efficiency during lautering"
..........-"enhances head stability and mouthfeel of the finished beer"
..........-"reduces filter clogging after fermentation"
..........-"prevents chill haze in the bottle"

He also states, "an acid rest has it's greates effect when the mash water is soft."

I'm overall happy with the pale German lagers I make, but I'm always willing to try for improvement. Are all of his statements accurate? (For example, how would it prevent chill haze in the bottle?) Also, why would an acid rest have it's greatest impact when brewing with soft water (keeping in mind that naturally soft water typically has a low pH)?

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Old 05-21-2009, 02:22 AM   #2
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I read the same, but didn't find it intriguing enough to look into further. I therefore don't have any great answers for you.

Regardless, wouldn't the beta glucanase benefits apply to any beer?

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Old 05-21-2009, 02:27 AM   #3
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I think the statement that many brewers do this is outdated. I rarely see a mash program with an acid rest in todays brewing science papers.

The comment about soft water may be rooted in that soft water has a lower pH buffering power which makes it easier for the acid rest to overcome this buffer and lower the pH.

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Old 05-21-2009, 12:54 PM   #4
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Is there any potential detriment to doing one? I might try a 15 min. acid rest on my next lager just to see if it noticeably affects anything.


Quote:
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Regardless, wouldn't the beta glucanase benefits apply to any beer?
I would think so, but acid rests on darker beers could lower the pH too much due to the acidity contributed by dark specialty malts.
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Old 05-21-2009, 03:44 PM   #5
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Please do and give a report. I'm convinced that some of the advances in malting are really geared to commercial breweries where time = money. For the homebrewer, this generally is not an issue. So if the malting has improved such that they can get an acceptable lauter without the acid rest to breakdown gums, that would speed the overall process and reduce the costs. For me though the question is always, "but how does if affect the flavor?" If I can skip a step with no affect on flavor I will. If it will enhance flavor, even though it isn't needed, I'll do it anyway. In my upcoming ales I'm going to include a protein rest. All of my latest lagers had one. I just tapped into my CAP and it has a tremendous head and a rich full body, even with using corn and fermenting with Wyeast's Danish lager yeast.

My goal in brewing is to try and brew truely great beer (at least to my taste buds). I'm not satisfied with just brewing decent beers. I like to drink beers that make me say, "Wow, that's great!" I think it is litle extra steps and attention to details that take a beer from being decent to really good. Sure I can cut a few corners and make a prefectly drinkable beer. If that was all I wanted though, I'd just go out and buy it

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Old 05-21-2009, 03:52 PM   #6
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Quote:
Originally Posted by pjj2ba View Post
My goal in brewing is to try and brew truely great beer (at least to my taste buds). I'm not satisfied with just brewing decent beers. I like to drink beers that make me say, "Wow, that's great!" I think it is litle extra steps and attention to details that take a beer from being decent to really good. Sure I can cut a few corners and make a prefectly drinkable beer. If that was all I wanted though, I'd just go out and buy it
Sounds like we have the same philosophy.

I'll plan on doing it... but I want to do it via boiling water infusion vs. direct fire. I don't want the mash running up so slowly through all those temps. I haven't run the numbers for water to grain ratio, but I'm sure it will be fine. By that I mean starting thick at 100°F and infusing up to 140°F without going too much over 2 qts. per pound. Then I can direct-fire it up to the next rest around 158°F.
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Old 05-21-2009, 04:24 PM   #7
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Quote:
Originally Posted by menschmaschine View Post
By that I mean starting thick at 100°F and infusing up to 140°F without going too much over 2 qts. per pound. Then I can direct-fire it up to the next rest around 158°F.
I have a Rye that I've used this method on. Don't have the capacity to direct fire, so used a decoction to get to saccharification, but infusion to get into the 140 range works fine. I've refined it from the recipe below to go in a little thinner (1qt/lb) and also infuse thinner (up to 2qt/lb). Saddly, I have not done a side by side to compare, but it does produce a tasty Rye.

http://www.homebrewtalk.com/f70/4rye-roggenbier-78905/

I'd also be interested to hear your results.
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Old 05-21-2009, 04:45 PM   #8
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I changed my decoction such that the main mash stays at acid rest temps during the decoction. Didn't like leaving it at protein rest temps all that time.

I mash-in to rest @ about 100 F just long enough to measure/correct pH and immediately pull the thick-mash decoction...then I immediately infuse the decoction with boiling water to quickly get it up to ~158-160 F and only rest for about 5-10 minutes (Iodofor comes out starch-negative every time after 10 minutes)...then add heat to get up to the boil. It shortens the decoction process a little. EDIT: Decoction pH does not increase much at all after infusion.

First brew I tried it on was the Dortmunder Export in my sig...it was brewed mid-March. I recently stole a pour and the head was noticably better than the previous similar light Euro lagers that had a long protein rest. It's def my best light lager yet.

Also, I'm almost sure I read somewhere that acid rests can take quite a long time to significantly lower the pH so I can def see why a brewery would not want to do it.

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Old 05-21-2009, 05:08 PM   #9
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Quote:
Originally Posted by AnOldUR View Post
infusion to get into the 140 range works fine.
Thanks. I looked at your recipe. Mine would be similar in concept.

I ran a quick recipe through Beersmith. It looks like, for 14.6 lbs of grain for an 11 gallon batch, I can start with 4.5 gallons of water for the acid rest at ~ 1.25 qts per pound. Then infuse up to 142°F with 3 gallons of water at 210°F for a ratio of ~2 qts/lb. That'll work.
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Old 05-21-2009, 09:34 PM   #10
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Have you guys found rice hulls necessary when doing a beta-glucanase rest? I am making a Wit soon and figured I would employ a glucan rest due to the grist being 50% unmalted wheat and oats.

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