Author Topic: rolling boil?  (Read 6069 times)

Offline homoeccentricus

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rolling boil?
« on: June 02, 2016, 09:59:03 AM »
As I now have a Speidel Braumeister with amazing temperature stability, I can now also control the boil intensity (the temperature can be set to +100C).  And so I was wondering what the latest insights are wrt rolling boils. I checked Kunze (v3) and he states that there is (was in the early 2000s) a tendency to reduce the boil intensity. If too many proteins are precipitated, this will have a negative impact on foam retention. Also, boiling too intensely will increase thermal stress.

Any thoughts on this?  Where's the evidence for us homebrewers?
Frank P.

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Offline hopfenundmalz

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Re: rolling boil?
« Reply #1 on: June 02, 2016, 11:48:19 AM »
Some of the older direct fired systems I have seen in action have vigorous boils, the wort is jumping up a half meter. It is impressive.

Newer systems like GEA-Huppmann and the Merlin systems are gentler, but have techniques to strip volitiles from the wort.
http://www.gea.com/global/en/binaries/JETSTAR_1015_EN_tcm11-12656.pdf
http://www.bidonequipment.info/pdf%20files/KRONES%20STEINECKER%20Wort%20Boiling%20Systems.pdf

Bamforth talks about the boil here, he does say you want a good boil. I may have to listen again to see if he says how vigorous.
http://beersmith.com/blog/2016/03/01/boiling-home-brewed-beer-with-dr-charlie-bamforth-beersmith-podcast-121/
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Offline homoeccentricus

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Re: rolling boil?
« Reply #2 on: June 02, 2016, 12:10:11 PM »
The gea folder states that their techniques keep foam-positive nitrogen in the wort and avoid thermal stress. So I guess we want that as well...
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Offline dilluh98

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Re: rolling boil?
« Reply #3 on: June 02, 2016, 01:46:57 PM »
Some of the older direct fired systems I have seen in action have vigorous boils, the wort is jumping up a half meter. It is impressive.

Newer systems like GEA-Huppmann and the Merlin systems are gentler, but have techniques to strip volitiles from the wort.
http://www.gea.com/global/en/binaries/JETSTAR_1015_EN_tcm11-12656.pdf
http://www.bidonequipment.info/pdf%20files/KRONES%20STEINECKER%20Wort%20Boiling%20Systems.pdf

Bamforth talks about the boil here, he does say you want a good boil. I may have to listen again to see if he says how vigorous.
http://beersmith.com/blog/2016/03/01/boiling-home-brewed-beer-with-dr-charlie-bamforth-beersmith-podcast-121/

In this interview Bamforth talked pretty extensively about how many larger scale breweries were not built to allow volatiles to escape efficiently during the boil and thus problems arose. I really think this is a non-issue for most homebrewers using kettles who are getting at least a good turnover of the liquid surface (rolling). I don't think "jumping out of the pot" is necessary at all at the homebrew scale. I never worry about it - particularly because my 10 gallon pot is relatively wide and thus I get even better evaporation.

Offline kramerog

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Re: rolling boil?
« Reply #4 on: June 02, 2016, 02:26:23 PM »
What is the deal with "thermal stress?"  The last time I checked boiling wort was a liquid without feelings and without a metabolism.

I thought that lowering the boil rate in commercial brewing systems was driven by energy savings, which conceivably can be very substantial for a big operation.  Could be entirely wrong on this point.

I suppose that the temperature of boils can be "considerably" higher than 100 *C if the kettle is deep enough, which is not a concern for homebrewers.  For grins, I looked at a steam table.  The boiling point of water/water at the bottom of 15-16 ft of water/wort is 232 *F, which could be a concern for commercial brewers. 


Offline mabrungard

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Re: rolling boil?
« Reply #5 on: June 02, 2016, 02:31:41 PM »
Based on the evaporation percentages that pro systems produce and the percentages we homebrewers often experience, it's my opinion that we homebrewers typically boil too hard and have too much exchange with the atmosphere...which results in too much evaporation.

Yes, the wort needs to be moving during the boil to help extract the elements from our hops and to expel undesirable elements from the wort. But we don't need the wort to be leaping from the kettle throughout the boil duration. I've gone to partially covering my kettle to help reduce the exchange with the atmosphere. In addition, I limit the boil vigor to the point that I can see that the wort is moving trub and hop particles throughout the kettle. The other thing I do at the end of the boil is to increase the vigor to try and expel any DMS that might have accumulated in the early boil. It seems to be working, but without comparative trials, its just conjecture on my part.

Boiling too hard, just wastes energy and you end up with a lesser volume of more concentrated wort. Since you can't produce kettle caramalization at boiling temps, that argument seems dubious to me. I think that perception that brewers say they achieve is just the result of the more concentrated wort.   
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Offline narcout

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Re: rolling boil?
« Reply #6 on: June 02, 2016, 05:28:06 PM »
What is the deal with "thermal stress?"

There's a bit of info on this in Section 2.6 of the low oxygen brewing paper along with a reference to Kunze on target evaporation rates.

Offline zwiller

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Re: rolling boil?
« Reply #7 on: June 02, 2016, 05:49:08 PM »
Any citations as to boil length?  I am pretty set on converting to a 30m boil now. 
Sam
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Re: rolling boil?
« Reply #8 on: June 02, 2016, 05:53:51 PM »
Any citations as to boil length?  I am pretty set on converting to a 30m boil now.

I have been doing short boils for a few batches now. Just up your hops and account for the reduced boil loss in your gravity estimations.

Offline zwiller

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Re: rolling boil?
« Reply #9 on: June 02, 2016, 06:06:15 PM »
Any citations as to boil length?  I am pretty set on converting to a 30m boil now.

I have been doing short boils for a few batches now. Just up your hops and account for the reduced boil loss in your gravity estimations.
Thanks.  I am hoping the software makes this easy...  2 hour AG brew here I come!   
Sam
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Re: rolling boil?
« Reply #10 on: June 02, 2016, 06:20:26 PM »
My spreadsheet is structure so that you can pick boil off rate and boil time from a drop down. Changing them changes my preboil volume requirement and subsequently my sparge volume estimate.

I then adjust my hop times and amounts to compensate. I like short boils because I don't have a dedicated brewing fridge for storing things like yeast and hops. I do small batches so I try to use all of a 1 oz. package of hops if I can for one batch.

Offline hopfenundmalz

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Re: rolling boil?
« Reply #11 on: June 02, 2016, 06:21:02 PM »
Ray Daniels said to avoid hot spots in you kettles, better stability I think was the reason NHC 2009.

The says foam, stability, undesirable flavors.
https://byo.com/malt/item/2816-better-boils-adding-body-mr-wizard
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Offline homoeccentricus

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Re: rolling boil?
« Reply #12 on: June 02, 2016, 07:04:04 PM »
Does anyone know anything more about thermal stress?  What it is and what it does...
Frank P.

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RPIScotty

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rolling boil?
« Reply #13 on: June 02, 2016, 07:14:14 PM »
Does anyone know anything more about thermal stress?  What it is and what it does...

As pointed out by narcout:




Take it with a grain of salt.

Offline homoeccentricus

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Re: rolling boil?
« Reply #14 on: June 02, 2016, 07:22:41 PM »
Yes, well, but it's also what Kunze says. Should I take Kunze with a grain of salt as well?
Frank P.

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