Anyone measure their rate of fermentation?

I ferment with a balloon as my airlock. The fun advantage of this is it allows you to roughly measure the rate of fermentation. If it takes roughly twenty seconds to fill a ~75ml balloon with CO2, then you can crunch the numbers and figure out that roughly 93.3 Quintilian (9.33x10^19) molecules of CO2* are being produced every second.

We also know that 2 molecules of CO2* are made from every sugar molecule. If the population size is known, you can then calculate the rate of fermentation per cell (since yeast are unicellular organisms). The hard part is counting them all.

If you also know the maximum alcohol tolerance of the specific yeast you are using, then you can estimate the appropriate amount of sugar to add to achieve a desired result, be it dry or sweet. This would be useful for recipies you've not yet tried before. Tracking the rate of fermentation at several hour intervals also offers insight into the alcohol tolerance of certain yeasts, assuming abundant sugar and appropriate temperature.

Footnotes:
* - and ethanol


EDIT: DATA POSTED! Click to go to post

tCan said:

We also know that 2 molecules of CO2* are made from every sugar molecule. Footnotes:
* - and ethanol

Click to expand...

Is that true for every yeast strain?

tCAN, I guess you are new to this infatuation. What's the point. Brew it, check it's fermenting, go drink and come back 2 weeks later. Watching is is not going to make it go quicker, or change how the beer is going to turn out.

Have fun with it.

Ehh I'm a geek for science and all. But use a hydrometer...

What happens when the balloon fills up all the way? Does it fly off your carboy and make farty noises as it flies through the air or does it pop?

maltoftheearth said:

Is that true for every yeast strain?

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As far as I know, it holds true for every 6 carbon sugar converted to ethanol.

Calder said:

tCAN, I guess you are new to this infatuation. What's the point. Brew it, check it's fermenting, go drink and come back 2 weeks later. Watching is is not going to make it go quicker, or change how the beer is going to turn out.

Have fun with it.

Click to expand...

The point? FOR SCIENCE!

kpr121 said:

Ehh I'm a geek for science and all. But use a hydrometer...

Click to expand...

Less awesome, and less informative. Also, I thought this was the science sub-forum?

acefaser said:

What happens when the balloon fills up all the way? Does it fly off your carboy and make farty noises as it flies through the air or does it pop?

Click to expand...

I've poked some tiny pinholes in the balloon which bleed the excess pressure.

maltoftheearth said:

Is that true for every yeast strain?

Click to expand...

It's approximately true for any strain that ferments (as opposes to respires) for the portion of the hexoses that are fermented.

C6H12O6----> 2 CH3CHOCOOH --> 2 CO2 + 2 CH3CHO --> 2 CH3CH2OH

As written many reactants, products and intermediate products (ADP, ATP, NAD, NAD+, H+, H2O) are left out here - that's why it doesn't balance WRT hydrogen)

But not all sugar goes down this pathway. Some is diverted for the formation of amino acids, some for sterol synthesis, some winds up in esters etc.

Balling found that 2.0665 grams of "extract" produce 1.0000 gram of alcohol, 0.9565 grams of CO2 and 0.11 grams of yeast biomass. This finding is the basis for the formulas we use to calculate alcohol production based on specific gravity change (extract consumption) but one could, of course, also use Balling's findings to estimate it based on production of CO2. Getting the weight of CO2 is a bit tricky. First off, all the CO2 that the yeast produce are not evolved. One could use the temperature tables to estimate the number of volumes of CO2 contained in each volume of beer and convert that to mass. The gas evolved would be tricky to measure too. Obviously the mass contained in a given volume is strongly dependent on pressure so you would need to know the pressure inside the balloon to determine the mass of CO2 in its known volume. You could tare the balloon and then weigh it when full but don't forget to correct the weighing for buoyancy - it would be a big factor here. Also don't forget to correct the weighing for the water vapor content.

Every brewer monitors his rate of fermentation first by the rate of CO2 production. If the CO2 is running steadily then its going full bore. When it slows to blurp.......blurp.......blurp then it's time for a hydrometer reading.

Thanks for typing that up! I just thought I'd add that some species, humans for example, will ferment with different products entirely. When humans ferment (as during vigorous physical activity) pyruvate is reduced to lactic acid. Lactic acid is a waste product and must be eliminated. In the presence of abundant oxygen, the pyruvate is instead converted to Acetyl-Coa which can be used in further energy production.

Other products of fermentation can include lactate, CO2, hydrogen gas, and methane. Of course, there also exists other types of energy production, anaerobic respiration results in a myriad of end products, but that's another topic.

Would this work?

tCan said:

will ferment with different products entirely.

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I should have said "ferments to ethanol". When making sauermalz, for example, we rely on L delbrukii to ferment sugars to lactate.

Hex said:

Would this work?

Click to expand...

I from time to time think about putting load cells under the fermentor mostly as an aid in filling, adding dilution water etc. I also thought about monitoring fermentation progress that way but decided it wouldn't be likely to work too well because:
1. Ostensibly, CO2 loss is all that is going on. The 0.11 g yeast biomass per gram of alcohol stays in the fermentor. But you also lose water vapor.
2. The load cells would have to be quite precise i.e. have to be able to measure gram or subgram level mass changes while at the same time having to be able to handle 200+ kg of beer plus the empty weight of the fermentor plus the weight of coolant.
3. Variabllity in the amount of coolant at the time of any particular weighing would probably mask the small changes in mass from CO2 loss.

ajdelange said:

I from time to time think about putting load cells under the fermentor mostly as an aid in filling, adding dilution water etc. I also thought about monitoring fermentation progress that way but decided it wouldn't be likely to work too well because:
1. Ostensibly, CO2 loss is all that is going on. The 0.11 g yeast biomass per gram of alcohol stays in the fermentor. But you also lose water vapor.
2. The load cells would have to be quite precise i.e. have to be able to measure gram or subgram level mass changes while at the same time having to be able to handle 200+ kg of beer plus the empty weight of the fermentor plus the weight of coolant.
3. Variabllity in the amount of coolant at the time of any particular weighing would probably mask the small changes in mass from CO2 loss.

Click to expand...

It could work on a smaller scale production though. If you were able to keep a smaller vessel of the same recipe at the same temperature, you could do it that way. I for example only have a 2 quart carboy (read "empty glass juice jug") that I'm experimenting with. During the most vigorous period of fermentation, I would expect to loose about half a gram of CO2 a day, which is an entirely readable amount by an inexpensive scale. As it slows, error is going to become a bigger part of your reading, but practical knowledge can still be gleaned ie. the trend of the data. All of this is just for fun though. By working backwards, and assuming you know a couple other variables, a hydrometer tells you most of what you need to know.

Also, about the water vapor loss. Are you talking about water evaporating and being forced out by the CO2?

tCan said:

Also, about the water vapor loss. Are you talking about water evaporating and being forced out by the CO2?

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Yes. After sufficient CO2 has evolved to expel the air from the fermentor headspace it contains CO2 and water vapor and the mix passes out through the airlock. But thinking about it for a minute this probably isn't a major factor. The vapor pressure of water at 20 °C (which is high for fermentation) is less than 17 mmHg and water vapor is less dense than CO2.

I'd also recommend using a balloon with pin hole so there will not be significant mass loss due to evaporation of the airlock solution with your small scale trial.

There will be many statistical errors to track down, including CO2 absorption in solution, but I think you will get an interesting data set and graph, post results here!

Hex said:

I'd also recommend using a balloon with pin hole so there will not be significant mass loss due to evaporation of the airlock solution with your small scale trial.

There will be many statistical errors to track down, including CO2 absorption in solution, but I think you will get an interesting data set and graph, post results here!

Click to expand...

On my next one. I'll start something over the holidays and track it. I've got an empty carboy.

ajdelange said:

Yes. After sufficient CO2 has evolved to expel the air from the fermentor headspace it contains CO2 and water vapor and the mix passes out through the airlock. But thinking about it for a minute this probably isn't a major factor. The vapor pressure of water at 20 °C (which is high for fermentation) is less than 17 mmHg and water vapor is less dense than CO2.

Click to expand...

Wouldn't it's lower density cause it to rise to the top of the headspace and be the first to be forced out? In any case, I think it's a more of a factor when measuring overall fermentation than when taking point readings.

I started a batch. A white wine. I managed to get a hydrometer from the neighbor so I'll be tracking both gravity and CO2 production. I'll graph it as % alcohol. I'll also include ambient temperature, which should be just under 70 for the whole run but I'll include it anyway. Please note that these calculations are rudimentary and only approximate. The trend data is really the only useful information that I'll be able to show.

Anyway, initial gravity is 1.098, so there's plenty of sugar.

tCan said:

Wouldn't it's lower density cause it to rise to the top of the headspace and be the first to be forced out? In any case, I think it's a more of a factor when measuring overall fermentation than when taking point readings.

Click to expand...

Let's suppose that the water vapor did rise faster than the CO2. Then the partial pressures of water vapor would be lower than the equilibrium value for the given temperature and more would leave the beer to balance the chemical potential. I don't think it does rise faster, however, because I think brownian motion keeps it mixed. I think it stays mixed and gets swept out with the CO2.

tCan said:

I ferment with a balloon as my airlock. The fun advantage of this is it allows you to roughly measure the rate of fermentation. If it takes roughly twenty seconds to fill a ~75ml balloon with CO2, then you can crunch the numbers and figure out that roughly 93.3 Quintilian (9.33x10^19) molecules of CO2* are being produced every second.

We also know that 2 molecules of CO2* are made from every sugar molecule. If the population size is known, you can then calculate the rate of fermentation per cell (since yeast are unicellular organisms). The hard part is counting them all.

If you also know the maximum alcohol tolerance of the specific yeast you are using, then you can estimate the appropriate amount of sugar to add to achieve a desired result, be it dry or sweet. This would be useful for recipies you've not yet tried before. Tracking the rate of fermentation at several hour intervals also offers insight into the alcohol tolerance of certain yeasts, assuming abundant sugar and appropriate temperature.

Footnotes:
* - and ethanol

Click to expand...

I think this is pretty cool.

ajdelange said:

Let's suppose that the water vapor did rise faster than the CO2. Then the partial pressures of water vapor would be lower than the equilibrium value for the given temperature and more would leave the beer to balance the chemical potential. I don't think it does rise faster, however, because I think brownian motion keeps it mixed. I think it stays mixed and gets swept out with the CO2.

Click to expand...

Ok. Right. I see what you're saying now. Plus the CO2 coming off the liquid so quickly would also probably help to keep things stirred up. Either way, there's nothing that can be done about it. Not with turkey basters and balloons for lab equipment

Coming along here. Some surprising results. Here's a taste. An almost entirely linear increase in ABV over time. The CO2 readings would not suggest this. If you look closely though, you can see that the latest reading is a little below the line of best fit. Nearing completion now, so stay tuned.

Can you include a picture of your test setup, and details of your methods?

Sure. I'll include that in my post after fermentation stops. Though a single trial is hardly exacting science.

Edit: For the record, yeast is one of the most studied organisms in all of biology. I'm sure this information is already out there, and more reliable than what I'm doing.

tCan said:

I'm sure this information is already out there, and more reliable than what I'm doing.

Click to expand...

You can include your historical references too!

Awesome thread! Thanks!

Ignoring until after peer review...

j/k, cool experiment. Thanks for putting it up here.

I'm really surprised at how tolerant Saccharomyces is of alcohol. I didn't see any bubbles last night, but while I was sleeping, I picked up another percent ABV. They've barely slowed down at all, and I'm nearing 13% and my hydrometer has almost bottomed out. The end of the trial may be when there's no more sugar! A little bit of reading shows that reaching 13% is normal, with complete cell death at 14%. So we're probably going to see an abrupt ending here.

Ok I'm just going to post the data I collected. I've included two charts which I think are the most interesting but you can obviously construct whatever you'd like from the data. I would have liked to overlay the two charts, but this doesn't seem possible with OpenOffice.

As per Hex's request, my methodology:

1 Welches white grape juice, with several inches of headspace plus sucrose (IG: 1.098, with an unmeasured combination of Hodgson Mill and Red Star active dry yeast. I assumed these yeasts to both be Saccharomyces cerevisiae, but possibly of different strains. This was done to try to improve the odds of getting an alcohol tolerant strain. Jug was left in room ~70F

The balloon was filled with water and then dumped into measuring cups and found to be almost exactly 1/2 cup or 115mL. The water probably stretched the balloon a bit, and some necking on the balloon would need to go around the mouth of the jug, so this was rounded down to 100mL. We're only looking for trend data here anyway.

When taking a CO2 reading, the balloon was pressed as flat as possible and allowed to inflate undisturbed. Time was called as soon the balloon stood upright. Two of these readings were taken, averaged, and then rounded to the nearest 5 seconds. The balloon method is too crude to assume anything more precise. This was done without moving the jug, making every effort not to jostle it which would release extra CO2, skewing the reading. Ambient temperature reading was taken at this time and used in the standard gas law equation to calculate mol CO2/sec: (n=(PV/RT))/sec

The jug was then moved to my bathroom sink area. Turkey baster, hydrometer, funnel and hydrometer testing tube are cleaned with antibacterial soap before every reading. Spinning or bobbing the hydrometer will remove bubbles from the hydrometer which can skew the reading. These Relative Density readings were used to calculate the ABV. The calculator at Winemaking Conversion Calculators - grapestompers was used as well as a table included with the hydrometer. These compose our alcohol % and alternative alcohol % respectively. In comparing a few online calculators, it seems the table included with the hydrometer errs a little on the high side, while the online calculator, a bit to the conservative. It is a safe bet that the actual ABV lies somewhere between the two. Again though, we're really only looking at the trend data.

Without further ado the spreadsheet: White Wine.xls

It's in .xls format. Let me know if there's any trouble, or if you'd like to know anything else I might have forgotten to mention here.

@HEX, I did take some photos, but I can't get them off my phone, it wont detect my microSD card, sorry. You're not missing out on anything you've not seen before, trust me.

Too cool! Don't have much time at the moment, but I did have a good idea. Next time you run this, use a stopper and a mylar, party balloon, mass it empty(stopper and balloon), then when it fills, mass it again and subtract the difference. CO2 is very heavy, you will be amazed how much a full mylar balloon weighs. All you need is a gram scale, and your measurement will improve. (Volume is vary hard to measure compared to mass.)

Later.

Why mylar? Are they easier to blow up or something?

Edit: Oh! Mylar! Yes. That would be interesting. Can't let it fill up all the way though. And that would be just about the saddest looking party balloon I ever saw!

It might be interesting to fit a polynomial to the alcohol data and then take its first derivative. This should have the same shape as the gas evolution curve as gas evolution and alcohol production rate are proportional. I'd do it but the new Excel is not backward compatible and I can't open the spreadsheet.

Yes, I ment to say that the mylar balloon should have a larger volume than the CO2 liberated, never fully inflating. I filled a mylar ballon once for a grow project to gauge moles of CO2 by mass in a closed grow chamber--surprisingly heavy. Mylar is not as porous as rubber, and with mylar there would be no pressure increase in your closed system, both attributes would improve the experiment's accuracy.

Correct me if wrong, your measured maximum rate of CO2 release is approximately 2.5E-5 mol/sec or 0.000025 mol/sec.

C02 has 44.0 grams per mol, so the maximum rate of mass loss from the must is 0.0011 g/sec. or 0.066 g/min or 3.94 g/hour.

You can easily mass that quantity with a triple beam balance or weigh it with a digital scale.

tCan, for some reason the typical home brewer thinks it's ok to track the depletion of sugar with a hydrometer, but the tracking of CO2 creation is frowned upon. Odd, since sugar depletion is skewed by alcohol production, but hey, what do we know.

You need to find a mass flow meter on Ebay, like this one:

SIERRA INSTRUMENTS INC TOP TRAK 824-1 GAS MASS FLOW METER | eBay

But if you expect to do 10 gallon batches you need a zero to 500 sccm range.

You also need this $29 data acquisition device:

DI-145 Data Acquisition Starter Kit

Hex said:

Correct me if wrong, your measured maximum rate of CO2 release is approximately 2.5E-5 mol/sec or 0.000025 mol/sec.

C02 has 44.0 grams per mol, so the maximum rate of mass loss from the must is 0.0011 g/sec. or 0.066 g/min or 3.94 g/hour.

You can easily mass that quantity with a triple beam balance or weigh it with a digital scale.

Click to expand...

Exbeerienced said:

tCan, for some reason the typical home brewer thinks it's ok to track the depletion of sugar with a hydrometer, but the tracking of CO2 creation is frowned upon. Odd, since sugar depletion is skewed by alcohol production, but hey, what do we know.

You need to find a mass flow meter on Ebay, like this one:

SIERRA INSTRUMENTS INC TOP TRAK 824-1 GAS MASS FLOW METER | eBay

But if you expect to do 10 gallon batches you need a zero to 500 sccm range.

You also need this $29 data acquisition device:

DI-145 Data Acquisition Starter Kit

Click to expand...

Eh, we're working with what we've got. Alcohol is serious business, but not THAT serious. I'm a starving college student. It's going to be balloons and turkey basters for a LONG time.

ajdelange said:

It might be interesting to fit a polynomial to the alcohol data and then take its first derivative. This should have the same shape as the gas evolution curve as gas evolution and alcohol production rate are proportional. I'd do it but the new Excel is not backward compatible and I can't open the spreadsheet.

Click to expand...

Right, the alcohol % is basically an area under the curve of the CO2 graph.The CO2 is a more direct measurement, but at the same time probably less accurate.

You say you can't open the spreadsheet? It should be in Office 97/2000 format. As far as I know, there's nothing on the windows platform out there that cant open that. Anyone else have that issue?

I'm glad you guys enjoyed this, I had fun doing it, and it's kept me busy over the holiday break. Cheers

tCan said:

...; there's nothing on the windows platform out there that cant open that...

Click to expand...

That's the key phrase. Versions of Office earlier than 2011 won't run on Lion and Excel 2011 won't open earlier versions of Excel spreadsheets which come from other platforms. Actually they open them but cell contents are not displayed, calculated or otherwise accessible.

I think that's the '64-bit question.' I'm on Lion, and found out that I can no longer run my versions of Photoshop and Illustrator. So, now I'm on Gimp and Inscape--open source software. You might want to see what OpenOffice can do...

I'm 46 now, and have collected a nice little science, engineering, and machine garage-lab--all previously owned equipment. There are a lot of guys like us, once we've settled down, who do the same. It's genuine interest like yours that gets us here. Also don't overlook your university's facilities, and your major study of interest, these are your formative years...

The fun here is that we're all amateurs for the most part, we do this stuff because we love it, and some of us even play well with others. It's fun figuring things out as a group and not worry about getting paid, as an exercise in Science, it keeps our minds occupied and out of trouble. It's always encouraging to see younger ones like us--your enthusiasm is contagious.

I think measuring CO2 in the yeast/sugar/alcohol/CO2, metabolic reaction, actually has the potential to be more accurate as ajdelange stated--you just haven't nailed down the method to measure it better than the hydrometer. For example, I would think about some form of degassing process that will help calculate CO2 in solution. You could test that, and create a fudge-factor, figured by temperature. It would only be relevant at the beginning of the process, until the solution became saturated, but you may be surprised that it changes during the process. Then I would try to calculate how much CO2 is ionized into Carbonic acid and bicarbonates, and this might be as simple as taking pH and TDS data. Also might be interesting how much Carbon is retained in the cells of multiplying yeast, that might become significant as your accuracy increases.

Here's the CO2 wiki.

Here's a saltwater reef tank article.

BTW OpenOffice opened your .xls file just fine! Thanks for making me download the software!

Hex said:

I think that's the '64-bit question.' I'm on Lion, and found out that I can no longer run my versions of Photoshop and Illustrator. So, now I'm on Gimp and Inscape--open source software. You might want to see what OpenOffice can do...

I'm 46 now, and have collected a nice little science, engineering, and machine garage-lab--all previously owned equipment. There are a lot of guys like us, once we've settled down, who do the same. It's genuine interest like yours that gets us here. Also don't overlook your university's facilities, and your major study of interest, these are your formative years...

The fun here is that we're all amateurs for the most part, we do this stuff because we love it, and some of us even play well with others. It's fun figuring things out as a group and not worry about getting paid, as an exercise in Science, it keeps our minds occupied and out of trouble. It's always encouraging to see younger ones like us--your enthusiasm is contagious.

I think measuring CO2 in the yeast/sugar/alcohol/CO2, metabolic reaction, actually has the potential to be more accurate as ajdelange stated--you just haven't nailed down the method to measure it better than the hydrometer. For example, I would think about some form of degassing process that will help calculate CO2 in solution. You could test that, and create a fudge-factor, figured by temperature. It would only be relevant at the beginning of the process, until the solution became saturated, but you may be surprised that it changes during the process. Then I would try to calculate how much CO2 is ionized into Carbonic acid and bicarbonates, and this might be as simple as taking pH and TDS data. Also might be interesting how much Carbon is retained in the cells of multiplying yeast, that might become significant as your accuracy increases.

Here's the CO2 wiki.

Here's a saltwater reef tank article.

Click to expand...

Thanks. Yup, the CO2 is certainly more difficult to track, especially when the CO2 is coming out of solution faster than it's being produced.

Hex said:

I'm on Lion, and found out that I can no longer run my versions of Photoshop and Illustrator.

Click to expand...

Lion doesn't have the ability to run the old Carbon (or was it Cocoa - never could keep that straight) stuff that was necessary when Apple was supporting both PC and Intel platforms. Had to buy new copies of Photoshop, Office and several other audio and video processing software. Word and Powepoint seem to be backward compatible. Excel is not though I expect they will fix that in an upcoming release.

Hex said:

I'm 46 now...it keeps our minds occupied and out of trouble...It's always encouraging to see younger ones like us-

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From where I sit 46 is "younger ones" but definitely embrace the sentiment.

stated

Hex said:

--you just haven't nailed down the method to measure it better than the hydrometer. For example, I would think about some form of degassing process that will help calculate CO2 in solution.

Click to expand...

If we consider a 5 gallon (call it 20 L) fermentation to 5% ABV we would produce about 1L of alcohol with mass 789 grams. The amount of CO2 produced in creating 789 grams of alcohol is 844 grams. All this leaves the solution except what stays dissolved when fermentation is complete. At room temperature the number of volumes of dissolved CO2 is about 1 volume. This number can be refined by use of the tables or formulas that give the number of volumes as a function of temperature and pressure. 20 litres of CO2 is 20/22.4 = 0.89 mole and weighs 39.2 grams. Thus the total CO2 produced is the weight of CO2 which leaves the fermenter plus what remains in the headspace and the beer. The 39 grams is about 5% of the total.

Thus if you can capture all the CO2 which escapes the fermenter, calculate the amount retained in the beer and in the headspace and add these to the amount which leaves the fermenter you would have a pretty good estimate of the total CO2 evolved from which the alcohol produced could be calculated.

Hex said:

Then I would try to calculate how much CO2 is ionized into Carbonic acid and bicarbonates, and this might be as simple as taking pH and TDS data.

Click to expand...

If you are referring to the pH of the beer that is influenced by a lot of other things besides the CO2 dissolved in it and the CO2 acidification is swamped by the other acids.

Hex said:

Also might be interesting how much Carbon is retained in the cells of multiplying yeast, that might become significant as your accuracy increases.

Click to expand...

That's accounted for in the Balling formula.


So the question is "How do we measure the mass of CO2 leaving the fermenter?" Use of flow meters is one idea if we can correct for temperature, barometer and water vapor but it seems simpler to just capture the CO2 in potassium hydroxide. For the example given above you would need about 2 kg of KOH which you could dissolve in 3 L of water for a total mass of 5 kg plus the tare of the flask. You would capture about 800 grams of CO2 so the job is to measure a change of about 800 grams with a tare of perhaps 5.5 kg. You won't do that with a postage scale but the requirement really isn't that tough. There may well be practical limitations to this approach (e.g. where to get potassium hydroxide by the kilogram). Something to think about tho.

tCan said:

...the CO2 is coming out of solution faster than it's being produced.

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Not so once equilibrium is reached. The outflow will then be the same as the production rate.