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What are your ways to split up your brew day/s?

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Adr_0

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I just like to see the data rather than dogmatically following a quoted figure who's experimental factors aren't being explained.
If someone has done the reading let us know or I'll try and get up to speed if time allows.
If the data doesn't exist on small volume boils I may find time to run some experiments and submit to the lab at my work.

Edit: This appears to be one of the papers many are quoting. Boil volume is not recorded in the methodology. It was a lager with two malts.

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1979.tb06845.x/pdf
Table IV in this study is interesting as it puts the SMM and DMS in ug/L terms, rather than 'equivalence'. Straight away, SMM is 164g/mole and DMS is 64g/mol so conversion of 1 SMM mole will result in DMS being 0.4x the ug/L of the SMM.

During the boiling stages the DMS level is much lower than 0.4x the SMM level (taking the 11min numbers of 305 and 18), suggesting that it's basically instantly boiled off - and suggesting that the limiting factor of the removal chain is the conversion of SMM to DMS.

Given there is a half life of 30min at 98.5°C, you should focus on your malt selection and your boil temperature (assuming you will ignore the recommended time advice). Ironically I would suggest that a taller kettle is a solution for a greater temperature as you should be greater than 100°C at the bottom of the kettle.
 

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good4whatAlesU

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If you're looking to accelerate the reactions in the boil, then it would be worth understanding the reaction kinetics (if anyone's actually done that research; it would be rather difficult). I think what a lot of people in this thread are angling at is: Yes, there is no data regarding boil volume, but the fundamentals of chemical reactions are well understood. Vessel volume does NOT have a direct influence on reaction kinetics. The only way it would affect it is via mass flow characteristics (increased the interaction rate of the molecules from differing boil seeding and convection), which is indirectly. This would only increase the reaction rate if the reaction is indeed limited by the work input. However, like most reactions, my understanding is that the SMM--> DMS is an equilibrium reaction, and that the reaction rate is primarily dependent on temperature. (EDIT: Try a pressure cooker to get a higher temperature and faster reaction?)

While I understand you want to (dis)prove your hypothesis, I believe a more holistic optimisation approach would be better.

Eg, you may find that an external boiler with a kettle pump will give you higher energy efficiency and mimic higher boil intensity due to the far greater turbulence. This is in fact how industrial brewing kettles work (they are often under partial vacuum with vapour recovery too).
Interesting, I did chance upon one kinetics paper from 2015 I think .. but will need more brain power (and sleep) to interpret. Agreed the higher boil intensity (under vacuum or pressure) is interesting and as ^Adr_0 suggests increasing temps beyond (above 100 oC). I've in mind buying a few disposable plastic kettles from Big W ($7.00 each) and having a play around.

Vessel volume can have a volume on kinetics at the extreme.. that is (sorry I'm playing devils advocate) for example boiling 1 mL for 90 minutes, will result in not very much DMS or SMM (or anything) - only a burnt residue. edit; that is why the early papers with low volumes appear to have run their experiments under reflux (so they didn't run out of liquid).
 

Adr_0

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Table IV in this study is interesting as it puts the SMM and DMS in ug/L terms, rather than 'equivalence'. Straight away, SMM is 164g/mole and DMS is 64g/mol so conversion of 1 SMM mole will result in DMS being 0.4x the ug/L of the SMM.

During the boiling stages the DMS level is much lower than 0.4x the SMM level (taking the 11min numbers of 305 and 18), suggesting that it's basically instantly boiled off - and suggesting that the limiting factor of the removal chain is the conversion of SMM to DMS.

Given there is a half life of 30min at 98.5°C, you should focus on your malt selection and your boil temperature (assuming you will ignore the recommended time advice). Ironically I would suggest that a taller kettle is a solution for a greater temperature as you should be greater than 100°C at the bottom of the kettle.
I should correct this to changes in SMM vs DMS, and include the periods where it's boiling and where it's not. Very interesting, but still the same point that SMM->DMS is the limiting reaction:
upload_2017-8-22_18-0-45.png


So during the boiling stages there is significant reduction in DMS, significantly less than the 64:164 ratio, so my point still remains correct.

The stages either side show an increase in DMS with a reduction in SMM which suggests the SMM is being broken down to DMS - and fairly slowly. There is also a fixed starting quantity of SMM per batch that you need to burn through, so, funnily enough, if you boil for long enough you'll break all the SMM down and boil off all the DMS.

Apparently the sensory threshold is 33ppb, FYI.
 

klangers

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Interesting, I did chance upon one kinetics paper from 2015 I think .. but will need more brain power (and sleep) to interpret. Agreed the higher boil intensity (under vacuum or pressure) is interesting and as ^Adr_0 suggests increasing temps beyond (above 100 oC). I've in mind buying a few disposable plastic kettles from Big W ($7.00 each) and having a play around.

Vessel volume can have a volume on kinetics at the extreme.. that is (sorry I'm playing devils advocate) for example boiling 1 mL for 90 minutes, will result in not very much DMS or SMM (or anything) - only a burnt residue. edit; that is why the early papers with low volumes appear to have run their experiments under reflux (so they didn't run out of liquid).
That isn't the effect of vessel volume as such, it's specific boiling power (watts/kg). You'd get the same effect if you kept a 20L boil and made the power 200 kW or something crazy.
 

good4whatAlesU

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That isn't the effect of vessel volume as such, it's specific boiling power (watts/kg). You'd get the same effect if you kept a 20L boil and made the power 200 kW or something crazy.
Cool, but would not gravimetrically (watts/ kg) or volumetrically (watts/ litre) be legit? Why must it be gravimetrically only? If volumetrically is legit than vessel volume plays a part.

Edit: Hopefully getting some costing from the lab this week for DMS and SSM analysis. If anyone is interested I can possibly PM. Idea for my own interest is to do a very short vigorous, low volume boil with my usual base malt and see what's what instead of cogitating. Will take samples every 2 minutes or so for 20 minutes (something like that).
 
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klangers

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Yeah, you can do it that way. I personally wouldn't because thermodynamics works on mass - volume is not really ever used for this kind of analysis. Specific heat capacity, latent heat capacity etc etc is all expressed as mass-based so your watts/L is just watts/kg divided by density. But that's still specific boiling power, whether it be watts/kg or watts/litre. Vessel volume doesn't play a direct role is all I'm saying. You need to analyse it more "pure" metrics.
 

good4whatAlesU

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Agreed from a theoretical viewpoint, but the real world size / shape/ surface area/ smoothness etc. must play an influence?

Anyway, apologies guys for being pedantic. I'll stop flogging a dead horse. If the opportunity arises - I'll just do some shorter low volume boils with my base malt and see if the DMS and SSM are below acceptable levels. If they are within spec then all good.
 
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