Lid on or off during boiling?

[Buffers brewery]

TLA's are a PITA.

TLA ?

 

[Hanglow]

Most homebrew systems still have far too much boil off. We tend to put far too much power into our boils. I think historically it was thought that about 10-15% boil off was needed, but most modern brewhouses now aim for 4% or less. So the best thing to do, as mentioned by DocAnna is to cover the wort for most of the boil (at a low a power as you can to get a rolling boil) but then leave it uncovered at the end. A less aggressive boil also helps with things like head retention, saves power etc

 

[Slid]

Three Letter Acronyms

 

[Clint]

Why does a less aggressive boil help with head retention?

 

[DocAnna]

Why does a less aggressive boil help with head retention?

Since head retention is directly related to protein concentrations, and different proteins denature at different temperatures, I would presume that the higher temperature from a prolonged rolling boil would denature a greater proportion of proteins, so reduce the proteins available for head retention.

Anna

 

[Clint]

Ok..so,are proteins responsible, sometimes,for hazy beer? And...so we add protofloc,etc. to counter this?

 

[DocAnna]

Ok..so,are proteins responsible, sometimes,for hazy beer? And...so we add protofloc,etc. to counter this?

My understanding it's a balance between the two with the amount of protein. I also found this that explains the issue about boil temperature and head retention
https://pubs.acs.org/doi/abs/10.1021/jf035125c"It was observed that the higher wort boiling temperatures (∼102 °C), resulting from low altitude at sea level, reduced the final beer LTP1 level to 2−3 μg/mL, whereas the lower wort boiling temperatures (∼96 °C), resulting from higher altitudes (1800 m), produced LTP1 levels between 17 and 35 μg/mL."
Basically high boil temperatures means the foam is more likely to loose the stabilisation proteins.

Anna

 

[MagnusTS]

I only understand about a quarter of this thread, but it looks very interesting.

 

[Benfleet Brewery]

I only understand about a quarter of this thread,

Really?! As much as that

 

[Buffers brewery]

Any thoughts about the effect on boiling temperature with the lid on or off? Never measured it but my instincts tell me the temperature would be (slightly) higher with the lid on than off.

 

[Clint]

Given that the wort is full of sugars how low or high a boiling point variation are we talking about? I assumed with it being mainly water it would boil at 100c unless you was up Everest or something...

 

[MmmBeer]

Reading this has forced me to browse through my training course notes again. There were 9 reasons stated for why wort is boiled, sterilisation, stabilisation (denaturing enzymes), evaporation (drive off volatiles, DMS etc.) bittering, aroma extraction, trub formation (coagulation of proteins), colour development (Maillard reaction), concentration and acidification (which improves flavour, texture and promotes yeast growth). A boil off of 4% was recommended during a one hour boil.

I used to run my grainfather with the lid on, until a couple of batches developed a sulphury aroma and taste to them, which I mistakenly assumed to be DMS. From then on I have run it with the lid off throughout the boil, hoping to eliminate it. I later discovered that I had been trying to remove the chlorine with campden tablets, but using twice the required amount and what I could taste were sulphites. Its going to be lid on from now onwards.

 

[DocAnna]

Just an apology really, I've been doing academic stuff for the last week or so and particularly this weekend.... think I've ended up being a bit OTT here with the technical stuff. Also feeling a bit embarrassed in retrospect since this is all rather theoretical and I don't have the experience that it perhaps sounds like I should! Normal service will resume and I'll stop quoting academic papers....

....I think it might be a symptom of drinking too little beer recently .

Anna

 

[strange-steve]

Just an apology really, I've been doing academic stuff for the last week or so and particularly this weekend.... think I've ended up being a bit OTT here with the technical stuff. Also feeling a bit embarrassed in retrospect since this is all rather theoretical and I don't have the experience that it perhaps sounds like I should! Normal service will resume and I'll stop quoting academic papers....

....I think it might be a symptom of drinking too little beer recently .

Anna

Absolutely nothing to apologise for, there are plenty of us here who enjoy these more technical discussions, even if we don't fully understand it :tinhat:

 

[Buffers brewery]

Absolutely nothing to apologise for, there are plenty of us here who enjoy these more technical discussions, even if we don't fully understand it :tinhat:

Hear hear!

 

[Pennine]

DMS is one of those flavours I want to try purposefully added. I am not sure if I have tasted it before. If you listen to the brulosophy folks they say it's not an easy thing to purposefully pollute your beer with, although maybe they should have done a short 10 minute lid on boil with a long hop stand instead according to @DocAnna

 

[Obadiah Boondoggle]

Hi, OK I'm blaming you lot for me ending up reading this technical article on DMS at 7:15 this morning since I was pretty sure phase equilibria of volatile solutes would mean the evaporation behaviour was a bit different from expected. If you really want your mind boggled at the maths then try this paper:
https://onlinelibrary.wiley.com/doi/pdf/10.1002/jib.301"Evaporation behaviour of DMS in an aqueous solution at infinite dilution – a review"

The short version is that things dissolved in lots of solution have a boiling point a lot closer to the solvent depending on the dilution behaviour. Eg salt water boils only at a teeny bit higher temperature despite lots of salt - 58 g in a litre for 0.5 C rise (at sea level atmospheric pressure).
Due to dilution DMS does not change the boiling point of the wort, so it won't boil off until 100deg, though a small amount will be lost at a lower temperature but only in the same water vapour also lost at that temperature. The effect of this is that it takes a lot longer than you would initially expect to remove the DMS. In addition the vapour pressure of DMS is higher than water so the water will preferentially condense, such that with a vented lid, the lid would be expected to preferentially condense the water to DMS but not entirely. The following paper demonstrates that the DMS on it's own is mostly removed after 20 mins of boil.
https://onlinelibrary.wiley.com/doi/epdf/10.1002/j.2050-0416.1979.tb06845.x"Control of the Dimethyl Sulphide content of beer by regulation of the copper boil"

However this also shows that the free DMS from the mash is far less of a problem than the DMS precursors that are converted to DMS during the boil. Due to this combined effect, only about half the DMS is boiled off after an hour. To further complicate things, more DMS is formed while the wort is cooled to pitch temperature while the wort is still hot but not boiling.
One of the key findings here was that for a half hour boil, the levels of DMS could be higher than the initial amount due to the precursor conversion due to the time the wort stays hot. The total amount of DMS at pitching is little different from the amount in the mash wort but the SMM precursor is a lot reduced.

So the take aways:
1) Boiling doesn't get rid of all the DMS but does reduce it's potential formation during fermentation
2) DMS is released at a near constant rate during the whole time of the boil, and a bit more is released at a rolling boil than a simmer
3) The most critical part for DMS formation is the time taken to cool the wort.
4) Due to vapour pressure more DMS than water will be lost in partial condensation, however some of the DMS formed during the boil will be constantly returned to the wort throughout the boil.

so... if you want to reduce DMS Boil with the lid off, boil vigorously either throughout the boil or at the end of the boil, and cool quickly.

Anna

[Small edit to correct a typo in the last sentence]

Thank you Anna

It's my fault that you had to get up so early because I started the thread

It really shows the value of such forums though

Thanks - I have learned a lot from your early morning research

 

[Obadiah Boondoggle]

I only understand about a quarter of this thread, but it looks very interesting.

Which quarter do you understand?

What about the other two thirds?

 

[DarrenSL]

The short version is that things dissolved in lots of solution have a boiling point a lot closer to the solvent depending on the dilution behaviour. Eg salt water boils only at a teeny bit higher temperature despite lots of salt - 58 g in a litre for 0.5 C rise (at sea level atmospheric pressure).
Due to dilution DMS does not change the boiling point of the wort, so it won't boil off until 100deg, though a small amount will be lost at a lower temperature but only in the same water vapour also lost at that temperature. The effect of this is that it takes a lot longer than you would initially expect to remove the DMS. In addition the vapour pressure of DMS is higher than water so the water will preferentially condense, such that with a vented lid, the lid would be expected to preferentially condense the water to DMS but not entirely. The following paper demonstrates that the DMS on it's own is mostly removed after 20 mins of boil.
https://onlinelibrary.wiley.com/doi/epdf/10.1002/j.2050-0416.1979.tb06845.x "Control of the Dimethyl Sulphide content of beer by regulation of the copper boil"

However this also shows that the free DMS from the mash is far less of a problem than the DMS precursors that are converted to DMS during the boil. Due to this combined effect, only about half the DMS is boiled off after an hour

This is an excellent post and spot on. Chemical reactions are not instant and take time (except explosives!) so the long boil breaks compounds down to create smaller more volatile by-products that eventually evaporate. 'Lid on' will capture the condensate and concentrate these byproducts. In most cases these byproducts are definitely undesirable.

I've worked with organosulfur/thiols and the smells are truly awful!

 

[Wynne]

Outstanding, thanks for this. I have a 550m³/hr extractor fan and a very short, pretty well-insulated duct run but I still have some problems with condensation on a cold day with a vigorous boil (5.5KW element). I have been wondering if there are ways to reduce the amount of steam produced by keeping the lid on for some/all of the boil, and in fact, boil kettles with a 1.5" tri clamp ferrules seem to me to have perfect built-in chimneys :)

Next time I'm feeling brave I'm tempted to try to modify my approach and only boil with the lid off for the first 20 mins and see if it makes any difference. It should save a good deal of power too. Though I get what you mean about chilling quickly, at least that's a variable that most of us will be able to keep almost constant, although we would need to factor in the extra post-boil volume not driven off, so chilling may take a fraction longer.

Could you connect your extraction duct directly to the top of the kettle?