Cost of the boil.

[jof]

@RoomWithABrew
From what I remember from my Physics degree & industrial placement you are correct.
Turbulent flow from a simmering boil is more than sufficient to rotate the liquid through the vessel to expose the top layer for evaporation of volatiles & diffusion into the air.

A vigorous boil would increase the rate of turnover of the top layer and would slightly increase the surface area.

Choosing a shallow but wide vessel to increase surface area would have more effect.

So, as I see it, if you want to minimise your boil time, boil hard,
But as this is about the cost of the boil, a slightly longer boil at a lower power will save you cash.

 

[Agentgonzo]

A classic example for new brewers to do the research and come up with their own conclusions.
'Beware of false knowledge, it is more dangerous than ignorance'.

Indeed. Study physics and chemistry at school. Understand the basic science of what happens when you heat a liquid. Understand what is meant by evaporation and boiling.

Don't just believe someone on a forum who's read a few books/papers and drawn their own conclusions.

 

[Cheshire Cat]

Don't just believe someone on a forum who's read a few books/papers and drawn their own conclusions.

Or someone that quotes “experts” who agree with their opinion and ignore those who don’t.

 

[foxy]

Indeed. Study physics and chemistry at school. Understand the basic science of what happens when you heat a liquid. Understand what is meant by evaporation and boiling.

Don't just believe someone on a forum who's read a few books/papers and drawn their own conclusions.

As you can see not my own conclusions from the links I have provided. Here are a couple more. Including a blog from yet another English Master Brewer.

https://beerandbrewing.com/dictionary/RZV7tB05MV/
https://www.asianbeernetwork.com/why-do-we-boil-wort-the-processes-taking-place/

 

[Sadfield]

Still don't see the experts saying steam is the conveyor of DMS except the learned @foxy.
Thank you for interpretation most valuable.

If it isn't, then there's no issue of letting condensate drip back into the wort as it is pure h2o.

 

[foxy]

I am not against anyone wanting to simmer their wort or not even boiling their wort. Even using a steam slayer when there is no need to in a home brew situation. Just the broadcasting that there is no need to achieve a rolling boil because they believe it is fine to do so.

 

[Agentgonzo]

Or someone that quotes “experts” who agree with their opinion and ignore those who don’t.

Indeed. For any given question, if you get a consistent answer from a variety of sources, you can be confident it's correct.

If you get a variety of different answers, you can be confident that none of them are 100% correct and it's probably a bit more complicated!

 

[foxy]

Indeed. For any given question, if you get a consistent answer from a variety of sources, you can be confident it's correct.

If you get a variety of different answers, you can be confident that none of them are 100% correct and it's probably a bit more complicated!

So who are we to believe? Brulosophy, Womans Day? Or the Master Brewers, Boulton, Briggs and Bamforth who have spent their lives in the brewing industry.

 

[Agentgonzo]

If it isn't, then there's no issue of letting condensate drip back into the wort as it is pure h2o.

Depending on the temperature of the surface the gas is condensing on, this is correct*. You're describing fractional distillation.

In the scenario of a kettle lid, you'll start off with everything condensing on the lid, which will raise the temperature of the lid. As the lid goes above the boiling point of DMS, the DMS will stop condensing, but water will continue to condense. The lid will now be raised in temperature to ~100° and a lot of condensation will stop. As the lid cools a tiny fraction, a bit more water will condense. In practise, this means the first bit of condensate (a minute or less) will contain DMS, but there is plenty of time for this to be boiled off again after it drips back into the wort.

With longer chimneys etc (larger setups/ commercial breweries etc), the atmospheric cooling of the chimney and the larger surface area will mean the surface of the chimney is a lot cooler, so you will get DMS condensing which would potentially drip back into the wort - hence the advice is to not let condensate drip back in. In reality in commercial breweries, there is a lot of condensation on the kettle/copper lid that drips back in anyway.

*In reality, physical chemistry is never that black and white. You'll actually get everything condensing back, just at different propositions (so at ~100°, it will be almost all water, but slight impurities of other distillates - at lower temperatures, you'll get a higher proportion of other distillates (but water will still be the vast majority of condensate when you are over the boiling point of the other distillates))

 

[fireworkmaster]

Not a theory a fact, Timothy O'Rourke is a UK Master Brewer, Charlie Bamforth mentions the same thing as does Milk the Funk in the link you posted.
As I have said before, I don't care how anyone else boils, I am thinking of the new brewer just starting out, set me back first 12 months of brewing taking in some of the information offered up on forums.

During the boil, the converted DMS is evaporated off due to its low boiling temperature of 37.3°C [1] and the convection currents of the boil. Unhomogenized boiling of the wort can be a cause of DMS (e.g. dead-spots where the wort doesn't mix throughout the boil kettle). Calculations have been proposed to determine if this is a problem for a given kettle (see reference) [13].

Though Scott Janish is a home brewer he does take the time to look up the scientific papers relevant to home brewers.

http://scottjanish.com/how-to-prevent-dms-in-beer/

As a absolute beginner I only understood bits but it was definitely interesting , I had a beer from a festival this summer that reminded me of asparagus , frankly it was not pleasant, I did wonder what was going on and this article has pretty much confirmed it was DMS.

 

[foxy]

With longer chimneys etc (larger setups/ commercial breweries etc), the atmospheric cooling of the chimney and the larger surface area will mean the surface of the chimney is a lot cooler, so you will get DMS condensing and dripping back into the wort - hence the advice is to not let condensate drip back in. In reality in commercial breweries, there is a lot of condensation on the kettle/copper lid that drips back in anyway.

Wrong again, commercial set ups have a drip tray inside the vapour vent catching the condensate and dispersing it on the outside of the flue so it doesn't go back into the wort.

 

[Agentgonzo]

So who are we to believe? Brulosophy, Womans Day? Or the Master Brewers, Boulton, Briggs and Bamforth who have spent their lives in the brewing industry.

Why do you have to pick one source to believe in and disregard the rest? This isn't religion - it's science.

Read them all. See if there are differences in their assumptions, their methods, their reasoning. Are some making assumptions that aren't valid for your scenario? Has there been a change in the equipment/subject matter/basic assumptions between different experiments that could explain the differences? Try to understand why one set of results or conclusions is different from another. Search for corroboration from other sources. If you still can't explain the difference, do further research or run an experiment to try to test the difference.

This is how science works. If one set of results conflicts with another, it's not just discarded as being "wrong". It's investigated to see why it conflicted.

 

[Agentgonzo]

Wrong again, commercial set ups have a drip tray inside the vapour vent catching the condensate and dispersing it on the outside of the flue so it doesn't go back into the wort.

Yes. That was my point. With larger chimneys you get condensation, so you want to catch and discard the condensate and not let it drip back in or let it escape in any other way.

Edit: ok, modified the wording of the original post to make my meaning clearer

 

[foxy]

As a absolute beginner I only understood bits but it was definitely interesting , I had a beer from a festival this summer that reminded me of asparagus , frankly it was not pleasant, I did wonder what was going on and this article has pretty much confirmed it was DMS.

Best advice I can give you as a new brewer is research what the qualified experts have to say.

Why do you have to pick one source to believe in and disregard the rest? This isn't religion - it's science.

Read them all. See if there are differences in their assumptions, their methods, their reasoning. Are some making assumptions that aren't valid for your scenario? Has there been a change in the equipment/subject matter/basic assumptions between different experiments that could explain the differences? Try to understand why one set of results or conclusions is different from another. Search for corroboration from other sources. If you still can't explain the difference, do further research or run an experiment to try to test the difference.

This is how science works. If one set of results conflicts with another, it's not just discarded as being "wrong". It's investigated to see why it conflicted.

Over the time I have been brewing, I have book marked enough pages from Wiley online to write a book. They are all scientific pages, Timothy O'Rourke one of your own leading Master Brewers who has taught other brewers I have downloaded his tutorials and you know what, they are all comparable in their findings.

Yes. That was my point. With larger chimneys you get condensation, so you want to catch and discard the condensate and not let it drip back in or let it escape in any other way.

Edit: ok, modified the wording of the original post to make my meaning clearer

But you didn't say that, you stated it drips back in.

 

[Agentgonzo]

But you didn't say that, you stated it drips back in

Which is why I clarified it. My original wording did not accurately convey my meaning. I'm sorry it caused such confusion and for the obvious aggravtion it caused you.

 

[foxy]

Which is why I clarified it.

Always a good idea to check your facts before replying.

 

[Agentgonzo]

As a absolute beginner I only understood bits but it was definitely interesting , I had a beer from a festival this summer that reminded me of asparagus , frankly it was not pleasant, I did wonder what was going on and this article has pretty much confirmed it was DMS.

That's surprising and quite sad that a commercial beer tasted of DMS. But now you know what it tastes like, and if it happens in any of your beers you'll hopefully recognise it. In this regard, you're probably a step ahead of most people. Plus, you know of lots of ways to avoid it if it it does happen.

Fortunately, the basic advice (boil for an hour with the lid off) easily gets rid of DMS.

 

[Agentgonzo]

Still don't see the experts saying steam is the conveyor of DMS

There's nothing special about the steam here. Once DMS has come out of your wort, it behaves like any other gas in the atmosphere and can escape. In the case of an open pot and a gentle simmer, it will be carried away by the air (convection currents and any breeze etc); and in the case of a closed pot with a rolling boil, it'll be carried away by the expanding steam (and anything other boiling chemicals in the wort) that get boiled off behind it and push it out of the way.

So you're both right .

 

[Sadfield]

If DMS removal is only a factor of the temperature exceeding its boiling point, how do wort strippers work? How is DMS removed during fermentation, at temperatures below its boiling point?

 

[Agentgonzo]

It is the agitation which removes the DMS and the steam which carries it away.

And for clarity (given that's the direction of this thread - taking the simplified general advice and examining it in detail), this is a good simplification. Agitation won't remove DMS by itself (put cold wort in an sealed vessel and shake the hell out of it for an hour - the DMS will still be there).

It is the molecular energy* (ie, heat) that drives DMS out of the wort in one of two ways. Boiling (at the bottom of the kettle next to the element converting the liquid DMS into a gas, that rises up as bubbles and out of the top of the wort) and evaporation (at the surface of the hot wort where it escape into the air). Agitation is also a major factor (even a gentle simmer at homebrew scales) moves the wort around quickly so that all parts of the wort come to the surface regularly to allow evaporation to occur much faster than if the wort was kept still.

Both are easily achieved by a standard boil.

"Beware of false knowledge, it is more dangerous than ignorance". Indeed . Often false knowledge can come from misunderstandings.


*And even this is a simplification. Evaporation can still happen (albeit at very low levels) at any temperature. Leave cold wort out in the open for long enough, unheated and unagitated and it will still evaporate away.