Anyone measure their rate of fermentation?

[Hex]

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.

 

[Hex]

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.

 

[Exbeerienced]

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

 

[tCan]

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

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.

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.

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

 

[ajdelange]

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

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.

 

[Hex]

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.

 

[Hex]

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

 

[tCan]

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.

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.

 

[ajdelange]

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

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.

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

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

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.

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.

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.

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.

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

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.

 

[ajdelange]

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

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

 

[Hex]

Happy Holidays tCan, I Gimped 'em for you.

 

[Hex]

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

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

Curious difference of opinions here...

Now, if we were talking distilled water, I'd say ajdelange was correct, but in reality we are talking about a varying solution which probably has varying CO2 solubility. More data please.

 

[tCan]

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

For most of the run yes. But as fermentation slows, that may not be true. Saturation does not necessarily mean equilibrium. Incredible how many factors there are to consider. I'm not hugely familiar with gas exchange in liquids so I could be wrong and it could be only a minor consideration.

For experimental purposes, an indicator might be used. Bromothymol blue is one that comes to mind. I don't know if you can drink it though. And I'm not willing to sacrifice that ability. :cross:

Happy Holidays tCan, I Gimped 'em for you.

AlcoholVsCO2.jpg

YAAAY! Thanks!

 

[ajdelange]

Ultimately, of course, the solubility of CO2 in fermenting wort/beer does depend on the composition of the solution. CO2 is, for example, approximately 10 times more soluble in EtOH than it is in water and Henry coefficient depends, thus, on the mole fraction of EtOH. The equilibrium concentration of CO2 depends on the Henry coefficient, the fugacity of CO2 over the solution and the activity of carbonic acid in the solution. But Henry coefficient is, for all practical purposes, constant until the mole fraction of EtOH approaches 0.2 ( in a 5% ABV solution it is about 0.016), at 1 atmosphere fugacity is equal to pressure and, as ionic strength in beer is in the first place low and in the second place does not change appreciably over the course of fermentation and as H2CO3 is not a charged species activity coefficient for H2CO3 will be a constant very close to 1 throughout. Thus, to the level we could reasonably make measurements, solubility of CO2 is constant being determined by pressure (1 atmosphere once the surface is blanketed by CO2) and temperature. The presence of extract also has an effect on the mole fraction of the solvent but in a 12 °P maltose wort the mole fraction of water is 99.3%.

That's the theoretical evidence. Practical data can be found in the Zahm and Nagle (ASBC) table which gives volumes of dissolved CO2 in beer as a function of temperature and pressure. These tables are used for the analysis of beers of all alcoholic strengths. If ASBC had found that failure to account for alcohol content, true extract etc. caused appreciable error then they would have prepared additional tables or given correction factors based on whatever parameter was responsible for the variation.

"Equilibrium" here does not mean chemical equilibrium of the system. Clearly a system in which a reaction (fermentation) is underway cannot be at chemical equilibrium. What it does refer to is equilibrium WRT CO2. If CO2 does not escape at the rate it is formed then the chemical potential of CO2 in solution rises to the point where it exceeds the chemical potential of CO2 in the gas over the surface of the fermenting wort. This causes CO2 to move from higher to lower potential i.e. into the headspace. This continues to the point where the potentials are equalized. WRT the headspace: the total pressure in a fermenter open to the atmosphere is 1 atmosphere. Thus the maximum partial pressure of CO2 in the headspace can be no more than 1 atmosphere and that is reached when CO2 from the ferment has displaced all the air. From then on at any time the concentration of carbonic acid exceeds the Henry coefficient gas moves to the headspace. Any time [H2CO3] < Khy gas moves to the wort. Thus the equilibrium condition here represents one in which the headspace is full of CO2 at fixed pressure and temperature, the wort is at fixed temperature and CO2 is leaving the wort at the rate the yeast produce it. Note: We define the Henry coefficient here such that [H2CO3] = pCO2*Khy with the units of Khy being mg/L-atm.

WRT the indicator - I'm not sure what you would expect that to tell you. Wort pH drops appreciably in the first few hours of a fermentation as the yeast establish an environment optimum for their well being (and suboptimal for competing organisms). Thereafter the yeast tend to buffer wort pH to a constant value dependent on the strain. Thus pH is more indicative of yeast strain than CO2 content. Using the nominal 1 atm CO2 pressure over ferementing beer (resulting in about 1 volume dissolved dependent on temprature) the pH would be, in water, about 3.9. More typical beer pH would be 4.5 or so (though pH of as low as 4 are found in some ales).

 

[Hex]

One unaccounted variable would be pressure, using tCan's balloon method. Each time the balloon inflates, pressure increases. Each time the balloon is deflated, pressure abruptly drops to ambient pressure. And that brings up a second, unaccounted variable, barometric pressure throughout the experiment....

I'd like to straighten out the blue, mol CO2, curve in the above diagram with more accurate data. I think you'd see a smooth slope instead of the bumpy one. Maybe a cloud passed by or the weather cleared at hour 50, and/or the vessel temperature dropped, causing more CO2 to be released for a period of time...

 

[Hex]

...or it could be a real observation that will lead you towards your thesis, too cool!

 

[tCan]

The ambient temperature was also up at least 2C at that time. But I think you are correct. I'm inclined to think that the 'wave' in the data is erroneous. I'd not expect the fermentation rate to increase again after reaching it's peak. A more linear fall off, like the rest of the graph shows seems likely.

I might continue to do this under a different method. Perhaps just count the number of bubbles coming out of an airlock per minute. Waiting twenty minutes for a balloon to fill up twice is not exactly my cup of tea.

 

[Hex]

Still won't account for barometric pressure changes. Log that and temperature too, and correlate.

 

[tCan]

Still won't account for barometric pressure changes. Log that and temperature too, and correlate.

Will it not? The pressure above the water in the lock still affects the pressures inside the jug? Interesting. I guess that's right. I now remember reading about a similar set of circumstances. Maybe in my Orgo or bio book. I'll see if I can find it.

 

[Hex]

All I know is that my still carboys start to bubble during a low pressure system. So I assume the affect is there throughout fermentation--when the barometric pressure is low, less CO2 can stay in solution, when high more will be retained, just like fluctuations in temperature. There is no real world STP (standard temperature and pressure), it's constantly changing.

 

[ajdelange]

The airlock is a mini-manometer. The difference between the water level in the 2 arms of the U is the difference in pressure between the headspace and the atmosphere. If the water on the carboy side is 1/2" lower than the water on the open side the pressure difference is 1/2" WC (water column). As gas is evolved in the carboy this difference increases until the lock breaks (blurps) at which point the pressures are equalized and the levels return to being the same. So just after a blurp the pressure in the heaspace is the same as in the atmosphere. Practically speaking, a dramatic pressure change would be 1" out of 30 (mercury inches this time) after passage of a strong front i.e. about 3%. The equilibrium saturation level for the beer would then change by about 3%. Given the methods under discussion here I don't think that would be an appreciable source of error. Were a flow meter being used its reading would be corrected for temperature (effects density of gas and water vapor content) and barometric pressure (effects density).

 

[tCan]

The airlock is a mini-manometer.

That's exactly what I was talking about! Thanks!

 

[ryanhope]

Cool thread, keep up the good work!

 

[tCan]

I just re-read the thread. What fun! I said some things wrong at certain points though. IDK what I was saying! Must've been the nature of the experiment if you catch my drift. hehe.

 

[Hermit]

Practically speaking, a dramatic pressure change would be 1" out of 30 (mercury inches this time).

Visions of mercury in my bubbler....:cross: