Author Topic: CO2 Purity and Why It's So Important  (Read 4490 times)

Offline Big Monk

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CO2 Purity and Why It's So Important
« on: January 19, 2018, 03:51:31 PM »
We have been getting questions about why people should be interested in CO2 purity and what damaging effects the O2 impurities within bottled CO2 can have on the finished beers of ALL brewers.

We have been working on a blog post for some time and we finally finalized and posted a write-up on it today:

http://www.lowoxygenbrewing.com/brewing-methods/carbon-dioxide-purity/

Let's discuss it!
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Offline Robert

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Re: CO2 Purity and Why It's So Important
« Reply #1 on: January 19, 2018, 08:25:31 PM »
Okay, you probably know by now that I'm not jumping onto your bus, but that I do always seek to optimize my own procedures.

Your advice says, jokingly perhaps, only brew lagers, they produce their own sulfites! Well, hey, I DO only brew lagers.  So I'm curious:

Does the sulfATE  concentration in the liquor affect the sulfITE level in beer?  If so, would the sulfate concentration, in order to have any significant protective effect, have to be higher than would be otherwise acceptable in brewing liquor for lagers? (I don't think I've  seen this on your website.)
Rob
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Offline Big Monk

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Re: CO2 Purity and Why It's So Important
« Reply #2 on: January 19, 2018, 08:51:54 PM »
Okay, you probably know by now that I'm not jumping onto your bus, but that I do always seek to optimize my own procedures.

Your advice says, jokingly perhaps, only brew lagers, they produce their own sulfites! Well, hey, I DO only brew lagers.  So I'm curious:

Does the sulfATE  concentration in the liquor affect the sulfITE level in beer?  If so, would the sulfate concentration, in order to have any significant protective effect, have to be higher than would be otherwise acceptable in brewing liquor for lagers? (I don't think I've  seen this on your website.)

The sulfites produced during fermentation are going to be yeast derived, so the amounts of Sulfate in the source water and that which is added in addition don’t drive that.

Sulfates, however, have the potential, if I’m not mistaken, to be broken down during fermentation into sulfides, which can contributed to sulfury aromas and flavors in excessive amounts in non-hoppy beers. Again, not 100% sure about that, but I recall having an email exchange with Dr. Bamforth about that.
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Offline Robert

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Re: CO2 Purity and Why It's So Important
« Reply #3 on: January 19, 2018, 09:02:32 PM »
Thank you! Curiosity satisfied.
Rob
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Offline narcout

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Re: CO2 Purity and Why It's So Important
« Reply #4 on: January 19, 2018, 09:29:43 PM »
Sulfates, however, have the potential, if I’m not mistaken, to be broken down during fermentation into sulfides, which can contributed to sulfury aromas and flavors in excessive amounts in non-hoppy beers. Again, not 100% sure about that, but I recall having an email exchange with Dr. Bamforth about that.

According to Kunze, that is true (see Section 4.1.3.5).  As I understand the text, yeast convert sulfate to sulfite, which is excreted by yeast after the growth phase and can then form sulphur dioxide.   
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Offline Wilbur

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Re: CO2 Purity and Why It's So Important
« Reply #5 on: January 19, 2018, 11:03:24 PM »
Nice write-up! Two thoughts, I believe you mean "<0.10%", not "<10%" at point 1. My other thought is you include the complete serving volume in your calculations, but a good chunk of that keg should be within industry acceptable levels.

Either way, a good reason for me to start spunding. Looks like my project list just got a little longer. For spunding, I see the website recommends transferring prior to fermentation completing, but typically have very fast fermentations. Any comments on using a dime/sugar solution? Thanks!

Offline HoosierBrew

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Re: CO2 Purity and Why It's So Important
« Reply #6 on: January 19, 2018, 11:38:11 PM »
Quick derail - Spunding freaking rocks. Carry on.  :)
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Offline Big Monk

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Re: CO2 Purity and Why It's So Important
« Reply #7 on: January 20, 2018, 01:27:12 AM »
Nice write-up! Two thoughts, I believe you mean "<0.10%", not "<10%" at point 1. My other thought is you include the complete serving volume in your calculations, but a good chunk of that keg should be within industry acceptable levels.

Either way, a good reason for me to start spunding. Looks like my project list just got a little longer. For spunding, I see the website recommends transferring prior to fermentation completing, but typically have very fast fermentations. Any comments on using a dime/sugar solution? Thanks!

I didn’t mean for it to be a %. It’s actually supposed to read 10 ppm. I fixed the blog post.

As far as your comment on a good chunk of the keg being under the industry maximum of 150 ppb, remember that we are being fairly charitable with our assumptions. We can’t reasonably assume that everyone is using 99.9% pure CO2, and in fact, most people are probably using 99.5% Industrial Grade, which contains upwards of 50 ppm O2 impurity. Granted, that’s also an assumption, and we can certainly point to many who are using beverage grade CO2, but as a general rule, people are using what’s available to them. As a quick comparison, let’s calculate what that does to the example given in the blog post:

For 99.9% Purity - DO = 1.42*30*2.5 = ~106 ppb

For 99.5% Purity - DO = 1.42*50*2.5 = ~177 ppb

Those are the numbers just for force carbonating the beer and not with serving factored in. Keep in mind that this also assumes 0 ppm of Oxygen content in the keg after purging (definitely not the case with all brewers). We also assume no oxygen pickup from transferring.

Also, as you increase desired carbonation level, these DO levels in the carbonated beer increase. For instance, let’s increase out target carbonation to 2.7 volumes:

For 99.9% Purity - DO = 1.42*30*2.7 = ~116 ppb

For 99.5% Purity - DO = 1.42*50*2.7 = ~192 ppb

Again, these are values without serving added in.

This is certainly not a scare tactic by any means. It’s just meant to shed some light on something people may not even have on their radar.
« Last Edit: January 20, 2018, 01:36:22 AM by Big Monk »
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle

"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur

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Offline Wilbur

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Re: CO2 Purity and Why It's So Important
« Reply #8 on: January 20, 2018, 01:41:54 AM »
Nice write-up! Two thoughts, I believe you mean "<0.10%", not "<10%" at point 1. My other thought is you include the complete serving volume in your calculations, but a good chunk of that keg should be within industry acceptable levels.

Either way, a good reason for me to start spunding. Looks like my project list just got a little longer. For spunding, I see the website recommends transferring prior to fermentation completing, but typically have very fast fermentations. Any comments on using a dime/sugar solution? Thanks!

I didn’t mean for it to be a %. It’s actually supposed to read 10 ppm. I fixed the blog post.

As far as your comment on a good chunk of the keg being under the industry maximum of 150 ppb, remember that we are being fairly charitable with our assumptions. We can’t reasonably assume that everyone is using 99.9% pure CO2, and in fact, most people are probably using 99.5% Industrial Grade, which contains upwards of and exceeding 50 ppm O2 impurity. Granted, that’s also an assumption, and we can certainly point to many who are using beverage grade CO2, but as a general rule, people are using what’s available to them. As a quick comparison, let’s calculate what that does to the example given in the blog post:

For 99.9% Purity - DO = 1.42*30*2.5 = ~106 ppb

For 99.5% Purity - DO = 1.42*50*2.5 = ~177 ppb

Those are the numbers just for force carbonating the beer and not with serving factored in. Keep in mind that this also assumes 0 ppm of Oxygen content in the keg after purging (definitely not the case with all brewers). We also assume no oxygen pickup from transferring.

Also, as you increase desired carbonation level, these DO levels in the carbonated beer increase. For instance, let’s increase out target carbonation to 2.7 volumes:

For 99.9% Purity - DO = 1.42*30*2.7 = ~116 ppb

For 99.5% Purity - DO = 1.42*50*2.7 = ~192 ppb

Again, these are values without serving added in.

This is certainly not a scare tactic by any means. It’s just meant to shed some light on something people may not even have on their radar.
Definitely, and there's a definite"hope and pray" to getting what you pay for, just take a look at that foundry in Japan. I'm excited to do a side by side sometime this summer with spunding. I think the focus on process, etc is great, I feel like there's been a lot of focus on ingredients. Love the chase for perfection.

Offline Andy Farke

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Re: CO2 Purity and Why It's So Important
« Reply #9 on: January 20, 2018, 05:17:22 PM »
It's nice to see the numbers summarized--thanks for posting this. When do these dissolved oxygen levels translate into measurable sensory perception on the homebrew scale? I of course accept cold side aeration as a concern (and have experienced it myself)...I just wonder about the tempo of appearance of detectable effects under homebrewery conditions.

Outlining two scenarios typical for my beer...

- I have a batch that is uncarbonated and in the fermenter, and want to serve it at a party within the next day or two. If I quick-carb (either cranking pressure and letting it sit, or crank and shake) using my typical beverage grade gas, when do things start to go south in a detectable fashion? Is it even a worry if I'm serving in a day or two and keeping it cold during this whole stretch?
- I have a batch that is uncarbonated, which I force carb (~1 week), and serve. In my house, stuff typically is on tap for 4-6 weeks before the keg is finished. Again, I'm keeping it cold (≤40F) during this whole stretch.

Relative to the term "accelerated staling," what is the practical sensory time frame for this, if the beer is kept cold? Are we talking 1 day? 1 week? 1 month?

Finally, for the additional 39.94 liters of CO2 described in the article (which tips the calculated dissolved oxygen over the 150 ppb mark), is that over the lifetime of serving the keg? I.e., you're not dumping that full 39.94 liters in on the first day...or second day...or even second week, necessarily. My sense is that the 156.6 ppb mark would be hit only at the very end of the serving cycle. Or am I misunderstanding that section of the article?

I should emphasize again that I'm _not_ disputing the effects of cold side aeration--I'm just wondering about how quickly they manifest at homebrew scales under homebrew handling conditions in a way that the typical taster can perceive them.
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Re: CO2 Purity and Why It's So Important
« Reply #10 on: January 20, 2018, 05:43:22 PM »
I should emphasize again that I'm _not_ disputing the effects of cold side aeration--I'm just wondering about how quickly they manifest at homebrew scales under homebrew handling conditions in a way that the typical taster can perceive them.

I completely agree.  Numbers are one thing, taste is another.
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Offline Robert

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Re: CO2 Purity and Why It's So Important
« Reply #11 on: January 20, 2018, 05:45:19 PM »
I should emphasize again that I'm _not_ disputing the effects of cold side aeration--I'm just wondering about how quickly they manifest at homebrew scales under homebrew handling conditions in a way that the typical taster can perceive them.

I completely agree.  Numbers are one thing, taste is another.
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Offline narcout

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Re: CO2 Purity and Why It's So Important
« Reply #12 on: January 20, 2018, 05:51:57 PM »
Do commercial breweries typically force carbonate their beer with non-fermentation produced CO2 (excluding bottle conditioned beers and RHGB compliant breweries)? 
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Offline denny

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Re: CO2 Purity and Why It's So Important
« Reply #13 on: January 20, 2018, 05:59:10 PM »
Do commercial breweries typically force carbonate their beer with non-fermentation produced CO2 (excluding bottle conditioned beers and RHGB compliant breweries)?

Almost every one I'm aware of does.
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Offline Big Monk

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Re: CO2 Purity and Why It's So Important
« Reply #14 on: January 20, 2018, 06:37:14 PM »
It's nice to see the numbers summarized--thanks for posting this. When do these dissolved oxygen levels translate into measurable sensory perception on the homebrew scale? I of course accept cold side aeration as a concern (and have experienced it myself)...I just wonder about the tempo of appearance of detectable effects under homebrewery conditions.

Outlining two scenarios typical for my beer...

- I have a batch that is uncarbonated and in the fermenter, and want to serve it at a party within the next day or two. If I quick-carb (either cranking pressure and letting it sit, or crank and shake) using my typical beverage grade gas, when do things start to go south in a detectable fashion? Is it even a worry if I'm serving in a day or two and keeping it cold during this whole stretch?
- I have a batch that is uncarbonated, which I force carb (~1 week), and serve. In my house, stuff typically is on tap for 4-6 weeks before the keg is finished. Again, I'm keeping it cold (≤40F) during this whole stretch.

Relative to the term "accelerated staling," what is the practical sensory time frame for this, if the beer is kept cold? Are we talking 1 day? 1 week? 1 month?

Finally, for the additional 39.94 liters of CO2 described in the article (which tips the calculated dissolved oxygen over the 150 ppb mark), is that over the lifetime of serving the keg? I.e., you're not dumping that full 39.94 liters in on the first day...or second day...or even second week, necessarily. My sense is that the 156.6 ppb mark would be hit only at the very end of the serving cycle. Or am I misunderstanding that section of the article?

I should emphasize again that I'm _not_ disputing the effects of cold side aeration--I'm just wondering about how quickly they manifest at homebrew scales under homebrew handling conditions in a way that the typical taster can perceive them.

I want to kind of take what you’ve said and parse it so we can hit everything you asked/commented on.

First, let’s be clear that we assumed 99.9% purity CO2. Let’s be honest with ourselves and say that of the people who keg thier homebrew, only a small minority of those people are going to be paying attention to/seeking out the purity spec of their gas. In fact, I think it’s safe to assume most people just use the 99.5% Industrial Grade they can locally source and refill. That means that as soon as you’ve carbed your beer to a modest level like 2.5 volumes, you are at 177 ppb, without serving, assuming a sufficient purge, closed transfers, etc. That puts you at the tipping point before you’ve even drank the beer.

So, we wanted to steer clear of any traditional/Low Oxygen debate here because it’s really not about that. I will say however, that while this should be a concern for ALL brewers, it’s a fundamental concern for us because the flavor impacts present themselves in short order. We are talking a few days to a week, at serving temperatures, after hitting 150 ppb that we are losing the fresh malt flavors, hop presence/flavor, etc., in Low Oxygen beers.

We have also had many of the people who transitioned from traditional methods to LO methods comment on how, from a flavor standpoint, they were now able to pinpoint certain flavor degradations across the life of a keg from their old processes. How long does this all take for the traditional homebrewer? It’s hard to say. We have a certain flavor profile distinctive to LO brewing that tells our taste buds when we’ve reached the tipping point. I would be on the lookout for the flavors described by Fix as “Stage B” oxidation flavors in PoBS, but also a diminishment of hop flavors, etc. obviously you want to make sure you are sufficiently purging your kegs, performing closed transfers, keeping the beer cold, etc.

As far as the serving pressure add to the sum total, you are correct. It’s not all added up front, but again, we made some assumptions here:

1.) You are sufficiently purging your kegs. That means liquid purging the ENTIRE keg, including the entirely of the headspace (liquid coming out of the PRV). If you aren’t doing that, you are adding to the DO in the finished beer.

2.) We assumed 2.5 volumes of carbonation. Obviously anything higher increases the DO in the finished beer.

3.) Again, we assume a grade of CO2 that is of a much higher purity than most are probably using.

Ultimately we just wanted to bring to light something that may not have been on people’s radar.
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle

"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur

Check us out at www.lowoxygenbrewing.com