Boil Vigor and Thermal Stress

[Pappers_]

@SEndorf sent me a note, saying that he had inadvertently hijacked another thread and taken it off topic but wanted to explore it in a separate thread with other, and asked if I could move his posts. I can't really move posts in the middle of a thread to start its a new thread, so am just cutting and pasting stuff here.

From @SEndorf

Where do you find evidence of improved beer quality with reduced boil vigor?

And a response from @RPh_Guy

Reducing "thermal stress" is a prominent goal in the scientific brewing community.

http://www.********************/uncategorized/low-oxygen-boiling/
^ cites Kunze

From Beer - A Quality Perspective by Bamforth
"In practice, brewers desiring more stable and resilient foam should attempt to minimize the severity of wort boiling within the constraints of their kettle design and the achievement of the other objectives of wort boiling including hop isomerization, protein precipitation and flavor enhancement."

Few articles as examples:
https://www.researchgate.net/profil...rt_boiling/links/5729bf0408ae2efbfdb9a30d.pdf


http://www.academia.edu/download/45993661/Wort_boiling_today20160527-17866-15m7xss.pdf

https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-2011-1017-01

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.476.4747&rep=rep1&type=pdf

https://www.mbaa.com/publications/tq/tqPastIssues/2002/Abstracts/0916-06.htm

 

[micraftbeer]

This doesn't really answer the question of vigor of boil and thermal stress, but I think is still relevant to the topic. I attended a presentation at HomeBrew Con in Portland a year or so ago talking about boiling (sounds so boring in hindsight...). Although it didn't say that thermal stress was bad, it did point out that a lot of the processes we typically associate with boiling are actually more about "wort turnover" rather than the level of surface rippling. In particular he talked about boiling off DMS pre-cursor, and that you achieve this with good wort circulation/turnover because it gets all of your wort up to the surface where the ripple boil can volatize that gas and send it up into the atmosphere.

And although he didn't delve into the "thermal stress is bad because..." topic, he noted that many production breweries focus their boil kettle design on circulation moreso than boil vigor.

So to me, my takeaway was that without knowing whether thermal stress from the boil was bad or not, I could achieve my boil goals without a raging boil, so why not just stick with a minimalist boil?

 

[Vale71]

So to me, my takeaway was that without knowing whether thermal stress from the boil was bad or not, I could achieve my boil goals without a raging boil, so why not just stick with a minimalist boil?

Well, for starters because I assume you're just boiling in a simple pot and not using a system designed for achieving those goals with minimal thermal stress. This means that with a very low boil it's very much possible that you won't achieve your targets of DMS elimination and hop utilization, just to name a couple.

One should also always consider when referring to industry-oriented research that the goal of 99% of the brewing industry is to produce very light (in color) to the point of being bland beers that are required to be very stable once packaged over a very long period of time under sometimes prohibitive conditions. Applying the same standards when brewing a doppelbock might not necessarily lead to the optimal result, so one must really take this as well as differences in equipment design into consideration to avoid comparing apples with oranges.

 

[Die_Beerery]

One should also always consider when referring to industry-oriented research that the goal of 99% of the brewing industry is to produce very light (in color) to the point of being bland beers that are required to be very stable once packaged over a very long period of time under sometimes prohibitive conditions. Applying the same standards when brewing a doppelbock might not necessarily lead to the optimal result, so one must really take this as well as differences in equipment design into consideration to avoid comparing apples with oranges.

However, most of the people producing these "pale bland beers" are making dopplebock on the same system.

Thermal and sheer stresses are real, and run rampant in the homebrew world.

 

[SEndorf]

I will start keeping track of some articles, but I've come across several opinions that in general, we boil too long and too hard.
For light pilsners, I've read both conflicting sides are desired - boil long and boil short.
I've always done 90 minute boils, and my electric system is fairly vigorous. I'm exploring if any changes might be preferable.

 

[Die_Beerery]

Your beer will thank you if you limit boil evap to under 10% absolute max(6-8% preferred), and have a nice gentle boil. I promise. Anything that says otherwise is rooted in pontifications and dogma, not science.

 

[mabrungard]

The article on Wort Boiling in Zymurgy provides a reasonably quick read and all the citations that support the need to treat your wort more gently. AHA now has a $4/month membership model and you can get access to electronic versions of archived Zymurgy magazines.

 

[archthered]

Timing is everything, literally yesterday I read an article in Zymurgy, May/June 2019 p. 36, talking exactly about this. I recommend checking it out if possible, especially if you are interested in the primary sources. It said that some things are affected by a hard boil while others are not and like most things it kind of depends on exactly what you are making as to what you want to do. In general a low boil is fine and possibly even better because TBA (thiobarbituic acid) increases with boil vigor. You want to limit TBA because it basically causes oxidation and early staling. Additionally a hard boil can reduce coagulatable nitrogen too much and reduce head retention.

This means that with a very low boil it's very much possible that you won't achieve your targets of DMS elimination and hop utilization, just to name a couple.

Interestingly it provides a lot of evidence showing that DMS can be eliminated in a shorter boil than most think EVEN with the lid on (which it suggests to reduce evaporation), long boils simply are not needed to eliminate DMS even in a Pilsner. Also it specifically discusses this point-

Although it didn't say that thermal stress was bad, it did point out that a lot of the processes we typically associate with boiling are actually more about "wort turnover" rather than the level of surface rippling. In particular he talked about boiling off DMS pre-cursor, and that you achieve this with good wort circulation/turnover because it gets all of your wort up to the surface where the ripple boil can volatize that gas and send it up into the atmosphere.

And yes turnover is good for many reasons, basically even with boiling the DMS may not escape if it never gets a chance to surface. The article suggests that using a pump or convection can help this, to use convection just off set your heat source so it's not in the middle.

There is alot more detail to this and the article touches on things I didn't but it's a really good article with a lot of good sources and visualizations. In short a vigorous boil is just generally not needed and can cause harm, as can a prolonged boil. This runs counter to some of what I've thought and done, I am likely to alter what I do and see what happens.

 

[SEndorf]

I will check out Zymergy. Thanks for the reference.
I'm rethinking some of my practices, which always brings a fun element to the hobby!

 

[Vale71]

However, most of the people producing these "pale bland beers" are making dopplebock on the same system.

Yes, with Sinamar and high gravity brewing. Thanks, but I think I'll pass.

 

[Vale71]

In general a low boil is fine and possibly even better because TBA (thiobarbituic acid) increases with boil vigor. You want to limit TBA because it basically causes oxidation and early staling.

Sorry, where did you get this information? TBA is toxic and AFAIK is not a natural constituent of wort, although it is used as a reagent for measuring the thermal load of wort (see MEBAK 2.4).

 

[RPh_Guy]

I just want to point out that the homebrewing boil kettle has way more surface area (relative to volume) than professional systems, so DMS and other volatile compounds have a much easier time escaping.

 

[Vale71]

That might be true for the smallest commercial systems (think brewpub) but anything larger than that has at the very least an internal boiler which increases convection n-fold so that surface area to volume becomes meaningless as a parameter.

 

[RPh_Guy]

That's my point. With our relatively huge surface area we don't need strong boils, lengthy boils, or advanced methods of circulating or forcing convection that you may find in articles about professional systems.

 

[Die_Beerery]

Yes, with Sinamar and high gravity brewing. Thanks, but I think I'll pass.

Vielleicht geht bei der Übersetzung etwas verloren. Welcher Dopplebock wird nicht mit hoher Schwerkraft gebraut? Was ist mit Sinamar los? Sie mögen die Weltklasse-Dopplebocks von Weihenstephaner oder die großen Münchner Brauereien nicht? Habe ich etwas verpasst?

 

[archthered]

Sorry, where did you get this information? TBA is toxic and AFAIK is not a natural constituent of wort, although it is used as a reagent for measuring the thermal load of wort (see MEBAK 2.4).

As I said it is all in the Zymurgy article, they specifically cite "A study on Kinetics of Beer Aging and Development of Methods for Predicting the Time to Detection of Flavour Changes in Beer by Li et al. I've seen nothing to suggest it is toxic, and could not find your source so I am still unsure about it being toxic. The reality is toxicity is a question of dose so even if it is toxic it may occur in a low enough level that it stales beer without being toxic to us, after all alcohol is toxic but that is literally part of the brewing process and for some the prime goal. The Zymurgy article does not go in to detail about how TBA is formed but it does say that long hard boiling is the "process" that leads to TBA. I take that to mean it is not a natural part of wort but forms through a long sequence of reactions rather than a simple and straight forward process. If you are interested in the process I imagine the source above probably goes in to detail about it, and if not they likely cite someone who explores this. I'm not particularly familiar with TBA in brewing, as far as I know it's just the result of some lipids oxidizing which could happen in boiling, so this is kind of new to me. I have not looked in to the primary source but may at some point. If this is something you are more familiar with I would love it if you would give a better citation (I could not find what you were talking about by googling MEBAK or MEBAK 2.4 but this may be one me, I've not had a chance to look much, a year may be helpful, I will look more later) I would like to look at your source to get familiar with this more.

 

[Vale71]

I don't have access to the Zymurgy article but I'll venture a guess that you might have misunderstood a reference to the standard method for measuring thermal stress in beer or wort, which uses TBA as the main reagent.
MEBAK 2.4 is the (European) standard method. All I could find is this link which is for the original version (German), sorry.

https://www.mebak.org/img/pdf/musteranalysen-eng/volume-ii-chapter-2.4.pdf

 

[madscientist451]

Putting scientific results aside for a moment, I've had lots of beer brewed on high-tech industrial systems that may have met the desired specifications, but the beer sucked. My low tech, no chill, thermally stressed, hot side aerated, less than optimal efficiency stovetop homebrew probably wouldn't do so well stored in cans in a 100F Los Angeles warehouse, but fresh out of the keg its better than (some) of the industrial beer I can buy at the store.
My apologies for hijacking a previously hijacked thread....

 

[archthered]

OK Vale71 I've dug into this a bit and think I know what is going on. In short, you are correct! I looked at the link you shared (thanks for that) as well as a few other things and TBA is definitely something added to indicate oxidative stress. You may know all of the rest of this but I'm going to spell it out for anyone else following this tangent of the conversation, it does so by reacting and changing color in the presence of a chemical that forms when lipids are oxidized, this occurs during a long boil as part of the Maillard reaction, and these chemicals do hurt shelf life by making the beer more stale.

So the Zymurgy article got the point right, just not the method. From rereading that section it seems like the author is not differentiating between the oxidative lipids which stale beer and the thing that tests for them, the TBA. Since the advice and implications are correct I imagine this distinction was made in an earlier draft but accidentally left out of the final, though maybe I'm just projecting.

At any rate the implication, that there is harm in boiling to vigorously so do so with your eyes open, is correct even if the explanation was a bit off. And I'm glad I understand this all now.

 

[Vale71]

Vielleicht geht bei der Übersetzung etwas verloren. Welcher Dopplebock wird nicht mit hoher Schwerkraft gebraut? Was ist mit Sinamar los? Sie mögen die Weltklasse-Dopplebocks von Weihenstephaner oder die großen Münchner Brauereien nicht? Habe ich etwas verpasst?

You're not from the original Hanover, right? Your translation is passable but you totally pooped it on high gravity. Your translation would imply brewing on a planet with higher gravity, like Jupiter or Saturn. The correct expression is "brauen mit höherer Stammwürze". BTW German is my third language after English so if I were to translate anything it would not be into German.

As for my post, I simply wanted to point out that the reason those large breweries use the same process for "brewing" a Doppelbock (in this case I would prefer the term "assembling") is just one of cost. They have a single (high gravity) process and they then "assemble" different beers through dilution and coloring agents. I like to think that I can tell such a beer apart from a double-decoction Doppelbock at the first sip and I'll definitely prefer the latter over the former. I'm well aware that the double-decoction beer won't be as stable as the other but I simply don't care as flavor takes precedence for me. Some of my best dark beers have undergone a double-decoction and a lenghty boil, their long term stability is not relevant to me as I simply don't let them get that old.

So, again, different scenarios, different priorities, different paramenters.