Low dissolved oxygen brewing techniques

[dent]

I spent some time today working on the fermenter-to-keg transfer setup. I wanted to be able to vacuum out a corny, and suck the beer from the fermenter with no air gaps anywhere. This was my first brew that I just used a plastic fermenter on, but the process will be pretty similar with the stainless 50L fermenter. It was nice to find the beer still has that quality malt flavour in it, for now.

I made the fitting simply by putting the silicon hose around a inline push-in joiner, which worked a treat.

First idea was putting a bunch of off-brand blu-tack around the top of the O ring seal of the corny lid - this worked pretty good for a while (some even got sucked in a little and I had to add more) but eventually the force was overcoming the off-centred lid clamps, and the lid was starting to tilt inward.

So plan B was to just turn the lid upside down. This works fine, however it forces the awkward step of taking the lid off and putting it back on the right way once the keg is filled. I gave in and did just that on this one - another idea is to modify a lid so it can't tilt down on one side. But purging the last litre in the top of the keg is much more feasible than trying to purge the whole thing. So I flushed out that last litre with CO2 about 10 times.

I didn't trust the fermenter tap to hold vacuum so that's what the irwin clamp is for.

The other issue is once the keg started to fill up, I'd lose vacuum due to the displacement, and I'd have to add more - but as the keg gets filled the foam would start to get in the suction tube attached to the gas post. So I had to use another spare keg as a bong, so no liquid would get into the vacuum pump.

Anyhow it's nice to confirm that a corny has enough structural integrity to hold a vacuum without imploding.

--

I did another brew today, I stuck with the LODO method however I was just brewing a smoked porter. I was too busy screwing around with the above I didn't really have time to prepare another stainless fermenter. So I went to see if it's possible to purge a cube. First I tried pulling a vacuum on one - that was pretty comical and did the cube no favours. Next I made a lid with a 8mm push in fitting, filled the cube with starsan, turned it upside down so the bubble was at the top. I bubbled CO2 through the starsan, and vented the bubble as much as possible a few times. Then I used CO2 to push the rest of the starsan out. All in all this used a lot of gas and I'm not really convinced it makes a complete purge - It's easy to leave the valve open a little too long and suck some air back in while trying to get the bubble out. I hooked the kettle tube up to the cube tap and loosened the lid to allow the wort in.

Anyhow I wasn't super fussed about making a LODO smoked porter but I still wanted to use the opportunity to iron out bugs in the process.

 

[Adr_0]

I personally use sodium ascorbate because it produces an equivalent NaCl instead of an HCl as ascorbic acid does. It doesn't acidify the water for every bit of chlorine removed, and instead produces salt.

I guess the three comparisons are below. Although I picked sodium ascorbate for chlorine removal, I'm not sure that it would be the best for O2 removal - some 'articles' say it is, but literature doesn't really back it up, except for this:
http://www.lighthouseinstruments.com/uploads/posters/LIGHTHOUSE_poster_assessing_oxygen_degradation.pdf

Not sure about at temps in the 60's, but it looks like SMBS is a hell of a lot faster. Rates are in the top-right - significantly increased with temperature. Unfortunately there's no comparison with everything at 65°C.

Seems to make sense if you consider dissolving SMBS in water:
Na2S2O5 + H2O >> 2NaHSO3 (sodium bisulphite)
2NaHSO3 + O2 >>2NaHSO4 (sodium bisulphate) [this reaction would be fast and readily performed]
2NaHSO3 + 2HOCl >> H2SO4 + 2HCl + NaSO4 (sodium bisulphite, SBS, reacts with chlorine in 1:1 to produce sulphuric acid, hydrochloric acid and sodium sulphate)
Practically speaking, if you have chlorine your pH will drop slightly for every bit of chlorine removed. If you have an excess of SMBS you will have a fair chunk of SBS left over - a sulphite - but if there's O2 around you will end up with a sulphate which is A-OK

Ascorbic acid with chlorine:
C5H5O5CH2OH + HOCl >> C5H3O5CH2OH + HCl + H2O (dehydroascorbic acid, a weak acid, plus hydrochloric acid which is pretty strong but not quite as significantly as the SMBS acids above)

Sodium ascorbate with chlorine:
C5H5O5CH2ONa + HOCl >> C5H3O5CH2OH + NaCl + H2O (same acid as above plus hydrochloric)

Both of the above won't be exactly the same if there is an excess, but will likely produce a similar weak acid.

If you're using CO2 blanketing, and pre-boiling into cubes (transferring with CO2) you might not quite need 100mg/L of SMBS - perhaps you only need 50mg/L if you're confident with your blanketing. You might be able to supplement vitamin C in with this too.

 

[dent]

I'm just gonna put this here..

--

This is a great post on the GB forums, about the commercial brewing aspect of all this.
http://forum.germanbrewing.net/viewtopic.php?f=49&t=436#p4215

 

[hotmelt]

Just a thought.Instead of playing around with vacuums and Co2 to add water to the mash tun,you could make something like this to prevent o2. Would allow you to monitor your mash and sparge better.

http://www.instructables.com/id/DIY-Anaerobic-Chamber-aka-glove-box/

 

[drsmurto]

I've been mulling this over for the past few days trying to find a few moments to piece together some thoughts.

Firstly, oxygen is part of the area of research I am involved in along with copper and sulfur chemistry in wine. Oxygen doesn't react with organic molecules (it's spin forbidden - a discussion of electron orbitals could follow but I'll leave that for now), it first is reduced by redox active metal ions such as Cu+ and Fe++ to the superoxide radical and further reduced (in acidic environments such as beer) to hydrogen peroxide by another Cu+ or Fe++ ion. The next step is the Fenton reaction where the most reactive of the species is formed, the hydroxide radical. This will react with just about anything including ethanol, the product of which is acetaldehyde. The kinetics are very fast and you won;t be able to undo the chemistry once it occurs. This article goes in to some of them chemistry - http://pubs.acs.org/doi/abs/10.1021/jf903127r

In wine, sulfite is used to control this by reacting with the hydrogen peroxide (not oxygen) to produce sulfate, a stable ion. SO2 is the molecular form and at the pH of beer, can be considered to not exist. It is instead present as bisulfite and sulfite.

So adding sulfite to your brewing water is the best defence against oxygen.

The downside to using sulfite is that yeast love it and use it to produce the sulfur containing amino acids, cysteine and methionine, but also release large amounts of hydrogen sulfide in the process. Yeast already produce sulfite (another reason there is no such thing as sulfite free wine (or beer)), the amounts produced are strain dependent.

Removing oxygen from water without using sulfite can be done easily enough with an airstone and an inert gas such as nitrogen. I do this routinely at work and within a few mins remove all the oxygen. I use a Presens oxygen sensor which uses luminescence to detect oxygen which enables me to measure the oxygen inside a sealed container without exposing it to oxygen and has a LOD of 1ppb (unlike the 1ppm that was mentioned for the cheap meter). I don't see why 1ppm is the cutoff for oxygen to make a difference to the resulting beer. From my research in wine that is more than enough to make massive changes to the chemistry.

The rest of this process I'll leave to the engineers to try and find ways to prevent oxygen from getting in.

 

[neal32]

I've been mulling this over for the past few days trying to find a few moments to piece together some thoughts.

Firstly, oxygen is part of the area of research I am involved in along with copper and sulfur chemistry in wine. Oxygen doesn't react with organic molecules (it's spin forbidden - a discussion of electron orbitals could follow but I'll leave that for now), it first is reduced by redox active metal ions such as Cu+ and Fe++ to the superoxide radical and further reduced (in acidic environments such as beer) to hydrogen peroxide by another Cu+ or Fe++ ion. The next step is the Fenton reaction where the most reactive of the species is formed, the hydroxide radical. This will react with just about anything including ethanol, the product of which is acetaldehyde. The kinetics are very fast and you won;t be able to undo the chemistry once it occurs. This article goes in to some of them chemistry - http://pubs.acs.org/doi/abs/10.1021/jf903127r

In wine, sulfite is used to control this by reacting with the hydrogen peroxide (not oxygen) to produce sulfate, a stable ion. SO2 is the molecular form and at the pH of beer, can be considered to not exist. It is instead present as bisulfite and sulfite.

So adding sulfite to your brewing water is the best defence against oxygen.
The downside to using sulfite is that yeast love it and use it to produce the sulfur containing amino acids, cysteine and methionine, but also release large amounts of hydrogen sulfide in the process. Yeast already produce sulfite (another reason there is no such thing as sulfite free wine (or beer)), the amounts produced are strain dependent.

Removing oxygen from water without using sulfite can be done easily enough with an airstone and an inert gas such as nitrogen. I do this routinely at work and within a few mins remove all the oxygen. I use a Presens oxygen sensor which uses luminescence to detect oxygen which enables me to measure the oxygen inside a sealed container without exposing it to oxygen and has a LOD of 1ppb (unlike the 1ppm that was mentioned for the cheap meter). I don't see why 1ppm is the cutoff for oxygen to make a difference to the resulting beer. From my research in wine that is more than enough to make massive changes to the chemistry.

The rest of this process I'll leave to the engineers to try and find ways to prevent oxygen from getting in.

With your chemistry background what do you make of the claims of copper turning your beer into undrinkable oxidized swill? Does the science confirm this?

 

[Adr_0]

Bugger about the keg... guess they are not rated for vacuum.

At work we've only really used vacuum once. Typically we dry out with nitrogen or natural gas to a certain dewpoint, but in this case we didn't want nitrogen left over as that would be a contaminant for the propane refrigeration. It went well, but very very hard work - main issue is leaks, assuming everything is rated for vacuum.

Bottling the other night, I thought this would be good:


It would basically be 1/2" vinyl tube about 25cm long to get to the bottom of a tallie, with a tee off to 8mm hose and a regulator set very low, i.e. something in the 0-10psig range. You would need only 0.5psig or so to act as a purge on the bottles, and this would allow the fill tube to be purged each time as well. You could put a valve in line to control the flow.

For using a plate heat exchanger, I wonder if the copper oxide layer could be dissolved with strong citric, then similar purge lines to CO2 are connected underwater (1-3psig this time) and then the citric carefully tipped out? It could then be connected up to your kettle and run a constant purge through the fermenter, heat ex and kettle.


The purpose of this would be to prevent firming an oxide layer again. Not sure if that's possible, but I'm thinking about how the Germans did inert casting about 100yrs ago...

 

[MHB]

Thanks DrS, always good to get the mechanisms, two extra questions.
Ascorbic Acid - Same reaction pathway? the IOB training on O2 suggests a blend of VitC and Meta Bisulphite - maybe just to keep the total amount of S lower.
Cu & Fe - can you think of anything that would get them out of solution - other than a RoMo water supply, a simple chelating chemical may be.
If I were going to try LoDO first thought would be to boil all the water (getting rid of Cl, F, O excess carbonate...) if we tosses a bit of Zn or Mg metal in to the kettle would that replace the Cu, Fe? Just happen to have a jar of Mg turnings...
Mark

 

[jyo]

I am continually amazed by the level of knowledge and ingenuity of members on this site. Great work Dent, and amazing contributions MHB, DrSmurto and others.

 

[drsmurto]

With your chemistry background what do you make of the claims of copper turning your beer into undrinkable oxidized swill? Does the science confirm this?

Never read that. It's been used in brewing for centuries as the primary metal to make the vessels out of. It is still used in many cases and is routinely found in distilleries. It's often added to wine to remove hydrogen sulfide.

In this particular case it does play a role.

Thanks DrS, always good to get the mechanisms, two extra questions.
Ascorbic Acid - Same reaction pathway? the IOB training on O2 suggests a blend of VitC and Meta Bisulphite - maybe just to keep the total amount of S lower.
Cu & Fe - can you think of anything that would get them out of solution - other than a RoMo water supply, a simple chelating chemical may be.
If I were going to try LoDO first thought would be to boil all the water (getting rid of Cl, F, O excess carbonate...) if we tosses a bit of Zn or Mg metal in to the kettle would that replace the Cu, Fe? Just happen to have a jar of Mg turnings...
Mark

Ascorbic acid is generally used in tandem with sulfite. There is still some debate as to the mechanism but my understanding of the chemistry is that it is not particularly effective in the absence of copper ions. In this case that becomes a catch 22.... Ascorbic acid gets reduced to dehydroascorbic acid and hydrogen peroxide which the sulfite mops up.

As for the removal of Cu and Fe, there is a product undergoing approval for use in winemaking (in Australia. It's already in use in Europe) that removes these 2 metal ions. It's called Divergan and is very similar to PVPP but the crosslinking step is slightly different. PVPP doesn't remove Cu and Fe from solution whereas Divergan does and it is quite effective at it. I'm doing some research into it at the moment in relation to the resulting sulfur chemistry in wine once you remove Cu and Fe.

Zn and Mg won't remove or do anything to Cu and Fe. Boiling water won't remove fluoride, you need RO for that. Carbonate content is reduced upon boiling but far from completely.

Another method of removing Cu and Fe is called 'blue fining'. Potassium ferrocyanide. No longer used in the wine industry in most countries as far as I am aware due to the highly unlikely chance of producing hydrogen cyanide and the cost of then showing it didn't form.

 

[Techbrau]

Hi there,

I'm one of the original authors of the low oxygen brewing document put out by the German Brewing Forum. I read the thread here and thought it was so cool how people on the other side of the world (I'm in the USA) have such great ideas to contribute to the discussion. It was our hope that by putting out the document we could kickstart some renewed interest in the role of oxygen in brewing, which would eventually turn into an open-source effort to come up with solutions suitable for home and craft brewers.

DrSmurto, the two major oxidative pathways that we hypothesized were 1) Fenton-like processes which you describe in detail and 2) oxidation driven via enzymes naturally occurring in the malt such as peroxidase, lipoxygenase, polyphenol oxidase, and others. It would be great to find a metal chelating agent with as few side effects as possible but I'm wondering where that would leave the enzymatic oxidation. Sulfite seems to suppress both pathways but I'm quite interested in investigating alternative methods as well. I have a technical background so I can kind of stumble along but I'm no chemist. Do you have any insight as to more surgical methods that we could use to fight the oxidative enzymes as well as the transition metals?

I think that we should be striving to use as little SMB as possible. The 100 mg/l we recommended in the paper is a bit overkill in my opinion but we wanted to publish a method that would work for people who might have leaky systems...nowadays I am using about 50 mg/l but I employ a floating stainless steel cap on my mash and lauter tuns which limits the surface area of the wort exposed to air. I also made sure that my pump lines have zero leaks and that generally my system is very tight when it comes to oxygen pickup.

In retrospect, not emphasized enough in the paper IMO is the impact of heat stress! I posted some pictures of what too much boiling can do to your wort here:

http://forum.germanbrewing.net/viewtopic.php?f=53&t=440

For anybody interested in exploring low oxygen brewing, our forum has a lot more information than is contained in the pdf, so feel free to take a look. We're just getting started exploring the subject and there's a still a lot of unanswered questions. You guys here clearly have a lot of expertise and it would be great to bridge our communities and work together in the pursuit of making better beer.

 

[klangers]

Techbrau, welcome and thanks for writing the original document!

There are a lot of knowledgeable people here who also like a discussion. Bridging communities is a great idea.

I think everyone agrees about oxygen pickup from atmosphere and the necessity to protect from this as well as removing DO from source water. What I don't think there is a lot of detail on, although touched on by DrSmurto, is the effect of metallic copper.

It has been used for centuries to make brewery vessels. I hypothesize that this was mainly due to the relative easy through which copper can be refined, worked and formed rather than for some chemistry reason.

Let's bear in mind that stainless steel is a 20th century invention, and from an engineering standpoint aside from thermal and electrical properties, is far superior to pure copper.

 

[MHB]

I've been doing a bit of study on LOX, the two parameters that were of interest were the pH range and the temperature deactivation (as with all enzymes)
Low mash pH (under 5.2, 5.1 is more sure) deactivate LOX. Temperatures above 62oC denature it as well.
Not a total solution, with modern well modified malt there is little or no need for Glucanase and Protease rests so mashing in hotter than 62oC and at lower pH should supress most of the LOX action.

Most of the LOX is degraded during malting, longer and hotter kilning reduces LOX, so darker malts will have a lot less to start with Pilsner > Ale > Vienna/Light Munich > Dark Munich.
Shorter mashes reduce the effects (within limits), Malt Peeling (removing the husk and germ) reduces the fatty acids....
No simple answers.

From what I have read so far I would have to use ultra pure water, adjust water chemistry to suit, and I think I would drop an airstone into the mash tun and keep a trickle of N2 flowing throughout the whole mash, like wise in any sparge water, perhaps even in the kettle.
Mark

 

[TSMill]

I'm just gonna put this here..

Cool, A 9L keg!

 

[neal32]

Techbrau, welcome and thanks for writing the original document!

There are a lot of knowledgeable people here who also like a discussion. Bridging communities is a great idea.

I think everyone agrees about oxygen pickup from atmosphere and the necessity to protect from this as well as removing DO from source water. What I don't think there is a lot of detail on, although touched on by DrSmurto, is the effect of metallic copper.

It has been used for centuries to make brewery vessels. I hypothesize that this was mainly due to the relative easy through which copper can be refined, worked and formed rather than for some chemistry reason.

Let's bear in mind that stainless steel is a 20th century invention, and from an engineering standpoint aside from thermal and electrical properties, is far superior to pure copper.

I've got a kegmenter on the way and am doing my first lodo brew this/next weekend. The caveat is that i have a copper herms coil and copper ccfc. Im reluctant to get rid of them (although i would if there was sufficient data/anacdotal evidence).

I hope someone does a side by side with stainless and copper to see the realworld effects.

 

[Adr_0]

Well I guess at pH 5-5.5 CuO dissolves easier that NiO that would likely be on stainless.

What I don't quite get us how this is oxidising the beer - in fact if this is stripped, dissolved O2 should form a stable CuO/NiO which then might drop out? The copper/nickel ions would act as a reducing agent, bonding with available O2. I believe to break these back apartments to Cu+ and O2- would require heat and a catalyst.

But, does dissolved CuO contribute to dissolved O2, which is then picked up on a DO meter? Does this then oxidise malt compounds? I would not have thought so, but if there is an elevated DO reading people might think it contributes to oxidation of the malt.

 

[MHB]

I've got a kegmenter on the way and am doing my first lodo brew this/next weekend. The caveat is that i have a copper herms coil and copper ccfc. Im reluctant to get rid of them (although i would if there was sufficient data/anacdotal evidence).

I hope someone does a side by side with stainless and copper to see the realworld effects.

I think you are rather missing the point. We are talking about Cu in the mash. By the end of the boil there are no enzymes left to react with the Copper (killing enzymes is one of the big 4 reasons we boil a wort).
That isn't to say that there are no effects from Cu in the boiled wort, Cu catalyses the formation of permanent haze, the same pathway that forms chill haze but it stays formed.
Copper in the kettle also helps Protein to coagulate, aiding in break formation, bit of a swings and roundabouts, you gain some advantages by using a Copper, and you get some down side as well.

Your using a Copper immersion chiller will have no impact on the effects related to LoDO, or Cu in the mash - any effects aren't related to the LoDO discussion
Want to start a new thread?
Mark

The Copper Recirc coil could be a different matter. I would be surprised if you didn't notice some improvement by reducing the O2 in the mash. The reaction with LOX doesn't need O2 (sort of oxidisation without O2) but is accelerated by Fe and Cu ions.
M
M

 

[drsmurto]

Well I guess at pH 5-5.5 CuO dissolves easier that NiO that would likely be on stainless.

What I don't quite get us how this is oxidising the beer - in fact if this is stripped, dissolved O2 should form a stable CuO/NiO which then might drop out? The copper/nickel ions would act as a reducing agent, bonding with available O2. I believe to break these back apartments to Cu+ and O2- would require heat and a catalyst.

But, does dissolved CuO contribute to dissolved O2, which is then picked up on a DO meter? Does this then oxidise malt compounds? I would not have thought so, but if there is an elevated DO reading people might think it contributes to oxidation of the malt.

CuO, which is all but insoluble in water, is soluble in acidic solutions. It will form 'free' Cu++ ions, the oxide anion results in a water molecule. This is not a redox reaction, simply copper ions dissolving, no oxidation/reduction takes place. The Cu++ ions now become available to redox catalyse any dissolved oxygen to the more reactive compounds I've already discussed (superoixde, hydrogen peroxide, hydroxide radicals).

As I mentioned previously, when Cu ions interact with O2 they do not form the oxide (CuO). What you are thinking of is the surface reaction between an elemental metal and oxygen which produces the metal oxide - it is a 2 electron oxidation/reduction - copper goes from 0 to +2, oxygen goes from 0 to -2. This is metal in the elemental oxidation state of 0, not +1 and +2 which is what they are in solution.

 

[Lyrebird_Cycles]

 

Yeast already produce sulfite (another reason there is no such thing as sulfite free wine (or beer)), the amounts produced are strain dependent.

 

As noted it is strain dependent, some strains actually produce none at all, notably the Weihenstephan wheat beer yeast (W-68 IIRC).

 

[Lyrebird_Cycles]

Well I guess at pH 5-5.5 CuO dissolves easier that NiO that would likely be on stainless.

The surface of properly prepared austenitic stainless is largely CrO2, that's why a citric rinse is used after caustic cleaning SS in wineries (since iron citrate is soluble the citric rinse reforms the passive surface). I've not seen any breweries use a citric rinse, though the use of acetic peroxyhydrate possibly has some effect (iron acetate is also pretty soluble).