49 replies to this topic

[3rd party JKor]

Now that I have my conical with side tap, it's so much easier to take gravity readings than before...but, as usual, I need to make it better. This morning it dawned on me that I could use a mass flow meter with a totalizer function (or any totalizing flow meter, really). to continuously monitor the progress of my beer without taking a sample. I'd imagine there's a pretty consistent amount of gas produced for every drop in gravity point. If you know precisely how much gas has been produced in your fermentation, you should know pretty precisely what your gravity drop has been.I may have to implement this in my brewery redesign.

[ThroatwobblerMangrove]

I'd imagine there's a pretty consistent amount of gas produced for every drop in gravity point. If you know precisely how much gas has been produced in your fermentation, you should know pretty precisely what your gravity drop has been.

I don't have any reason to think it is or is not consistent - what makes you think this? You could definitely take some data to test your hypothesis though

[3rd party JKor]

I don't have any reason to think it is or is not consistent - what makes you think this? You could definitely take some data to test your hypothesis though

I would think it's consistent because the there is a precise amount of carbon dioxide produced for each unit mass of sugar that is converted to alcohol. The ratio of monosaccharides to disaccharides may effect the number, I'm not sure though. I still need to do some more research. I bet Basser could shed some light on the subject.

[ThroatwobblerMangrove]

I would think it's consistent because the there is a precise amount of carbon dioxide produced for each unit mass of sugar that is converted to alcohol. The ratio of monosaccharides to disaccharides may effect the number, I'm not sure though. I still need to do some more research. I bet Basser could shed some light on the subject.

Yeah - I can see how it could be consistent but at the same time there are a lot of variables I don't understand. I just e-mailed my friend Tyler at the Portsmouth Brewery as well as this is the kind of question he might know the answer to.

[chuck_d]

"Carl Joseph Napolean Balling studied the relations between extract and ethanol levels from an emperical point of view in order to tak into account losses that occur in real fermentations. The main los is due to the yeast cells' use of carbohydrates for growth as opposed to ethanol production. Balling's measuremens showed that:2.0665g of ferementable extract -> 1 g of ethanol + 0.9565g of CO2 + 0.11g of losses."- George Fix, Principles of Brewing Science p. 92The point of the work wasn't to use CO2 to measure gravity, but this might be a starting point for you to try. I would of course measure gravities as well in order to check to see if your measurements conform. I think his point was to get a number for how much extract would be needed to produce a certain amount of beer at a specific alcohol level. The only problem I'm not sure this actually takes into account (being empirically derived it might) is the difference in CO2 production betweeen the EMP pathway and sterol synthesis. Both processes release CO2.

[gnef]

You would have to measure your volumes precisely. Some other variables could be trub dead space, temperature, and solubility of CO2 in solution at that temperature, which could vary depending on gravity itself. The temperature of the wort will also be variable throughout the day, as well as through stratification of the wort itself - I believe the center would be warmer than the outside, which the geometry of your conical would influence as well.All in all, I think you could get a good approximation, but there are definitely a tremendous number of variables at work.Now you could also capture the CO2 to recycle...

[3rd party JKor]

Also, when you think about it, a hydrometer tells you for every drop of .001 in density, there is a specific gain in alcohol content. Now, hydrometers may not be exact, but implicit in it's scale is that the fermentation/wort characteristics are close enough for all beers to say that the loss in gravity of .001 always produces about .133 %abv (@60F). Being that the production of a molecule of alcohol in fermentation is directly related to the production of CO2 (you can't produce a molecule of alcohol without producing a molecule of CO2), you should be able to directly correlate CO2 volume to loss in gravity.

[3rd party JKor]

You could also put the fermenter on a scale, or install a pressure transducer in the bottom of the fermenter. As long as you know the exact volume/depth of beer, you'd know your SG.EDIT: Actually, it would be even better to install two pressure transducers in the side of the fermenter that would both be submerged in liquid during fermentation. You could easily find the distance between the two and put together an equation; SP. GR. = f(diff.press.)

Edited by JKoravos, 30 May 2009 - 11:37 AM.

[3rd party JKor]

"Carl Joseph Napolean Balling studied the relations between extract and ethanol levels from an emperical point of view in order to tak into account losses that occur in real fermentations. The main los is due to the yeast cells' use of carbohydrates for growth as opposed to ethanol production. Balling's measuremens showed that:2.0665g of ferementable extract -> 1 g of ethanol + 0.9565g of CO2 + 0.11g of losses."- George Fix, Principles of Brewing Science p. 92The point of the work wasn't to use CO2 to measure gravity, but this might be a starting point for you to try. I would of course measure gravities as well in order to check to see if your measurements conform. I think his point was to get a number for how much extract would be needed to produce a certain amount of beer at a specific alcohol level. The only problem I'm not sure this actually takes into account (being empirically derived it might) is the difference in CO2 production betweeen the EMP pathway and sterol synthesis. Both processes release CO2.

Good info there, thanks.I wonder how consistent the CO2 production from EMP vs. sterol would be from batch to batch?

[3rd party JKor]

Now you could also capture the CO2 to recycle...

Uh oh....

[ThroatwobblerMangrove]

Uh oh....

If you keep your primary sealed up from some point onward it will carbonate itself. That's a pretty good reuse that some small breweries do.

[chuck_d]

Good info there, thanks.I wonder how consistent the CO2 production from EMP vs. sterol would be from batch to batch?

Yeah, I mean, for that formula, it might not even matter, it might have ended up being some sort of average based on real fermentations (which is what I think Balling was trying to do) and so he doesn't even get into the line between how/why a CO2 molecule was produced just that it was. I just wanted to get you something to work with, but my chemistry is kind of weak. Not sure why, but I've always had a mental block in chemistry compared to physics. I'd have to read more to understand how that was developed.

[chuck_d]

If you keep your primary sealed up from some point onward it will carbonate itself. That's a pretty good reuse that some small breweries do.

Yeah, some brewing literature makes the disctinction between this and priming. A lot of homebrewers refer to priming as natural carbonation, while other brewing literature calls this method natural carbonation and keeps priming separate, especially stuff that deals with the math of the situation. Priming may or may not conform to the Reinheitsgebot while natural carbonation always does.

[Winkydowbrewing]

What the heck do you guys do for a career? I think I have to start hitting the books again...

[Jimmy James]

I think using a surrogate like CO2 to infer gravity through the process is a good idea. Still what I don't understand is why someone hasn't developed some sort of hydrometer that is integrated into these fancy conical fermenters. There are sight glasses sometimes built into these things. Why not have something like a port with a vertical glass tube and hydrometer. When you charge the vessel with wort the tube would fill up and you'd get your OG. Over time as fermentation progresses you'd get a continuous gravity reading. Maybe you'd need two ports running into the vertical glass tube a couple inches apart near the bottom so yeast could flocc out and wort/beer could still exchange through an open port above the trub that would form.

[chuck_d]

I think using a surrogate like CO2 to infer gravity through the process is a good idea. Still what I don't understand is why someone hasn't developed some sort of hydrometer that is integrated into these fancy conical fermenters. There are sight glasses sometimes built into these things. Why not have something like a port with a vertical glass tube and hydrometer. When you charge the vessel with wort the tube would fill up and you'd get your OG. Over time as fermentation progresses you'd get a continuous gravity reading. Maybe you'd need two ports running into the vertical glass tube a couple inches apart near the bottom so yeast could flocc out and wort/beer could still exchange through an open port above the trub that would form.

It would only work if you're doing open fermentation. There is slightly more pressure in the fermenting wort and the headspace than the ambient pressure. CO2 is going to come out of solution in the sight glass or be pressurized. I'm not certain how the pressure change would affect the reading of the hydrometer, but as I understand it you're supposed to degas fermenting wort/finished beer for hydrometer readings (I know I currently do this). So it might not even be a trustworthy reading if you had a hydrometer constantly floating in your fermenter even with an open fermentation.

[3rd party JKor]

I think I just want an excuse to buy a flow meter.

[Slainte]

I think it's a dumb idea because the other reason to take samples is to taste it. Not just measure the gravity.

[3rd party JKor]

I think it's a dumb idea because the other reason to take samples is to taste it. Not just measure the gravity.

It's all going to end up in the same place, right? In mah belly!!!

[Lagerdemain]

Just as a point of contrast, I don't take any gravity readings whatsoever after I test for O.G. Somehow my beers still turn out great.