How to find alcohol pecentage for non-standard brewing method?

[salmosa]

I have recently made a few batches of makgeolli, a traditional Korean drink. Makgeolli is usually translated as farmers rice wine in English but it is not a very accurate name as it is not related to wine at all, I like to think of it as more of a rice beer. My problem is in finding the alcohol percentage of my original product.

My final product should be diluted with water to an alcohol concentration near 5%, but I am unable to find a method to determine the alcohol percentage of my original product. Two problems are confounding my ability to get an initial hydrometer reading to calculate alcohol percentage.

1) The rice mash that is fermented has a consistency similar to cooked oatmeal and thus a hydrometer would simply stick in it but would not float so that I can not get an initial reading (this Korean site has photos of the preparation of a typical mash http://blog.naver.com/PostView.nhn?blogId=sdr1976&logNo=90109257810).

2) Even if I added enough water for a hydrometer to float freely, all of the fermentable sugar is locked up as starch in the rice grains and thus is not dissolved in the water (Aspergillus oryzae fungus enzymes are used alongside the yeast to catalyze the conversion of starch to sugar). If the sugar is not dissolved in the water, it is not possible to get an accurate measure of the specific gravity.

Does anyone have an idea for finding the alcohol percentage of my brew?

 

[ehedge20]

Can you strain the liquid out?

 

[IrregularPulse]

What is done after the mash? Or does fermentation take place in the mash?

 

[salmosa]

Fermentation takes place in the mash, the Aspergillus oryzae enzymes and yeast are both working at the same time.

Initially, there is not much liquid that can be strained out, if it were strained it would mostly be water because the rice is still solid. It is only during fermentation that the starches in the rice are broken. At the end of fermentation, all of the rice is digested leaving a much larger liquid portion.

 

[ajdelange]

Given that the "extract" is solid (or semi solid but definitely not liquid) starch going into the fermentor here I don't see how Ballings formulas are going to help.

I suppose you could assume that rice (given that it is huskless) has 100% extract potential and calculate an original gravity on that basis e.g.: 1 kg rice + 9 liters of water is 10 °P. You might perhaps improve on that somewhat by looking up extract potentials of rice in a brewing text (it's probably less than 100% but more than 80%).

Another thought might be to mix in the Apsergillus but no yeast so that liquefaction of the starch takes place w/o fermentation and then measure the "OG" of that. Would probably have to heat before adding the enzyme to kill any wild yeast on the rice.

Unfortunately, there is no simple, straightforward method available to home brewers by which alcohol concentration can be determined. The not so simple methods aren't really available to home brewers either. To get a number you would have to submit the sample to a lab equipped to do alcohol determination

 

[salmosa]

Thanks ajdelange for your input. I would like to get a more direct but not exact measure to find how changes in the recipe affect the final result. Getting a mass spec or gas chromatography reading is the best method but difficult to access as you mentioned.

Do you think measuring the released volume of CO2 would be very accurate? (assuming that the molar ratio of CO2 and ethanol are equal according to the reaction C6H12O6 + Zymase > 2 C2H5OH + 2 CO2)

Would the production of methanol, acetic acid, or other compounds be very significant when the temperature is around 25C to 30C thus reducing the predicted yield?


Wikipedia's ethanol article mentions a sensor for measuring concentration.

Infrared ethanol sensors measure the vibrational frequency of dissolved ethanol using the CH band at 2900 cm−1. This method uses a relatively inexpensive solid state sensor that compares the CH band with a reference band to calculate the ethanol content.

Does anybody know a part ID for this type of sensor or anywhere that sells them?

 

[ajdelange]

Thanks ajdelange for your input. I would like to get a more direct but not exact measure to find how changes in the recipe affect the final result. Getting a mass spec or gas chromatography reading is the best method but difficult to access as you mentioned.

Distillation and measurement of the density of the distillate is time consuming and troublesome but doable at cost which is best not discussed with Mrs but perhaps bearable. The gear for the distillation is pretty straight forward (mantle, distilling flask, Kjeldahl adapter, condenser, condenser adapter, volumetric flask) as is the procedure. It is where you determine the density of the resulting water solution that things get a bit tougher. 5% ABV is not enough to be read on a Tralle hydrometer so you need a more accurate means than that. A pycnometer used with care can get you a fairly good number. But those cost $200 and you need an analytical balance you can read to 0.1 mg. The other method of density measurement is a digital meter but those are thousands of dollars.

Another thought would be to distill 400 mL of sample (rather than the traditional 100) plus 200 mL DI water, collect 400 mL and redistill that to 100 mL thus concentrating the alcohol to 20% which you could read on a Tralle hydrometer.

Do you think measuring the released volume of CO2 would be very accurate? (assuming that the molar ratio of CO2 and ethanol are equal according to the reaction C6H12O6 + Zymase > 2 C2H5OH + 2 CO2)

If you could collect all the CO2 and bubble it through lye and then precipitate calcium carbonate with calcium chloride or something of that sort I suppose you could get a decent answer.

Would the production of methanol, acetic acid, or other compounds be very significant when the temperature is around 25C to 30C thus reducing the predicted yield?

The biggest error source here (unless the product is really sour) would probably be the yeast biomass. The Balling formula makes an assumption about how much of the extract winds up as yeast. It varies, of course, but as it is only about 5% total shouldn't throw you off that much if you knew what to use as the nominal value which probably isn't that different from what it is for beer fermentation.


Wikipedia's ethanol article mentions a sensor for measuring concentration.



Does anybody know a part ID for this type of sensor or anywhere that sells them?[/QUOTE]

 

[bengerman]

send it to a lab, or, if it finishes very dry and clear, you can theoretically use a vinometer.
they're not 100% accurate, and i haven't been able to determine to what degree they are inaccurate. i have one, but i had a hard time using it (the directions that came with it are translated from french, rather poorly, by the looks of it.)

 

[ajdelange]

Problem with the vinometer is that its calibration depends on the surface tension of dry wine. Beer and this cocoction don't have that same surface tension and thus won't read accurately.

Another thought along these lines in ebuliometry. It doesn't work with beer because beer foams as it boils. Perhaps this stuff doesn't.

 

[DrJerryrigger]

First of that's a "vino-o-meter" I don't know why they add an extra "o", but they do.
As stated; the viscosity will not be a good test for abv as there will be starch strands of various lengths to mess with things. For the home brewer; I think distillation sounds like the most feasible way, though you wouldn't have great accuracy. Also it's of questionable legality even for scientific testing purposes.

The way that seems to fit the purpose best would be to just go by taste. This is after all the most important quality.
Though... if you were to calculate to potential starch and sugar content of the rice, get a SG reading of the finished product. Then dehydrate the spent rice and weigh it. Calculate how much of that is actually unused starch. Theoretical you could get rather accurate estimation... I would have to do a lot of research to figure that out, but it seems as though it would be possible. I would also not know how the yeast cake should fit into things, and a lot of denser starches would likely fall in to it...

Just some thoughts, I sure I didn't help

 

[remilard]

First of that's a "vino-o-meter" I don't know why they add an extra "o", but they do.
As stated; the viscosity will not be a good test for abv as there will be starch strands of various lengths to mess with things. For the home brewer; I think distillation sounds like the most feasible way, though you wouldn't have great accuracy. Also it's of questionable legality even for scientific testing purposes.

Stills with a capacity of less than a gallon and used for laboratory purposes are not subject to TTB regulation.

http://www.ttb.gov/spirits/faq.shtml#s3

 

[bengerman]

First of that's a "vino-o-meter" I don't know why they add an extra "o", but they do.

o reary?

(i did spell it wrong, but there's only one o.)

 

[ajdelange]

Stills with a capacity of less than a gallon and used for laboratory purposes are not subject to TTB regulation.

http://www.ttb.gov/spirits/faq.shtml#s3

True, but only if they are not used for separation of ethanol. Irrespective of the volume of the still, if it is used for separating ethanol it is subject to regulation. See the FAQ at the URL you gave.

I went to considerable trouble a few years back to get permission from what was then BATFE to distill (in a 250 mL flask) beer for the purposes of alcohol and diacetyl determination. I had to file an equipment list, the ASBC MOAs, a pledge that the samples would be discarded etc. I have a letter granting me permission to do these tests - but I'd never be able to find it if they demanded it.

Distillation produces quite accurate results. With a properly conducted procedure the recovery of ethanol is over 99%. Nevertheless, uncertainty in recovery is the largest contributor to the error budget amounting to about 0.02 % ABV. Total uncertainty is about 0.03% ABV. This assumes that you can measure the density of the distillate accurately enough that the contribution to the error budget is less than 0.02%. That requires about to 5 significant digits and this is where the method's biggest disadvantage lies. With accurate pycnometry I'm guessing you could attain perhaps 0.1% uncertainty.

 

[ajdelange]

o reary?

(i did spell it wrong, but there's only one o.)

Must be a different brand. Mine is Vino-o-meter.

 

[DrJerryrigger]

The wording on the distillation thing doesn't make me feel confident. They really don't want you to distill ethanol, and what defines a laboratory. It's just a bit of a gray area if your doing it in your home and not in an established lab.

I guess there are two on the market. My LHBS sells these:

I only remember the extra "o" because it sounds so stupid.

 

[ajdelange]

It's just a bit of a gray area if your doing it in your home and not in an established lab.

But they did write me a letter saying that I could do it in my home if I met all their conditions.

And that was in the days when BATFE was not a fun bunch of guys. Today, TTB seems a lot more flexible. There are nano breweries and craft distilleries springing up all over the place. TTB seems cooperative, will work with people, returns phone calls etc. I considered doing proofing for a guy who wanted to make his grandmother's limoncello commercially. He was constantly in touch with those guys and I consulted with their lab staff about the interference from lemon oil in the distillate (they don't worry about so I wouldn't have to either). But I have to admit the thought of the Feds poking around here was not comforting. Haven't heard back from the would be liquer maker so I guess I won't have to worry about that.

 

[DrJerryrigger]

Oh so I guess I'm typing slow tonight. A few new posts wile I wrote the last one.
ajdelange, thank you for confirming my fears of anything slightly related to distilling ethanol. (I dislike dealing with paper work for things I don't really need to do anyway)


I did a little more searching on the vinometer, and it seems there are many spellings of it. I guess that works for copyright laws in France...

 

[ajdelange]

Wikipedia's ethanol article mentions a sensor for measuring concentration.



Does anybody know a part ID for this type of sensor or anywhere that sells them?

Looking back over the thread I see I forgot to respond to this. I believe this is the principle on which Anton Paar's Alcolyzer works. The Wiki quote (which does not appear here) mentions "relatively inexpensive". Given Anton Paar's prices (and they give all their profits to charity) I'd have to ask "Relative to what?".

 

[DrJerryrigger]

I'd have to ask "Relative to what?".

"The Alcolyzer from Anton Paar was originally released early in the year 2000. With its initial price tag of about $11,000" - www.winebusiness.com

Even if it's gone down 90% its out of my price range.

 

[ajdelange]

I think the early models used sound velocity but AP found that wasn't as accurate as IR and so changed the design. Don't quote me on this - I'm recalling a casual conversation with the rep. Also if I'm recalling correctly they are closer to 20K now.

 

[makmak]

The difficulty in Makgeolli ABV measurement is because carbohydrates are still being broken down at the same time fermentation is taking place. So using the difference between beginning SG and ending SG will not give an accurate ABV calculation. I am trying to distill some of the makgeolli (using a small pot, reversing the lid and putting ice on it to make it condense) and use a V/V refractometer (used for measuring ABV in distilled sprits) to read the real ABV. So far this method seems promising. Haven't perfected the condensing part but last night I got an ABV reading of 11% when the beginning SG and ending SG estimated only 7.5% ABV.

 

[shresthasoman]

So, did you figure out how to measure the alcohol content?

 

[MackerelQ]

At the hazard of unduly resuscitating a possibly dead thread, I've just begun (first batch just today) brewing makgeolli. The question regarding calculating ABV for this product reared its ugly head when I realized the saccharification happens at the same time the fermentation occurs. I do have an idea on how to measure the ABV, however. Perhaps anyone interested can provide a sanity check on my hypothesis.

So, here goes. The starter culture you use for making makgeolli, nuruk, is a combination of grain (wheat), molds, bacterias, yeasts, and enzymes. The molds create the enzymes protease, lipase, and amylase. Each of these enzymes have an optimum temperature range for effectiveness and a temperature threshold at which they are denatured. The same can be said for the yeasts contained in the starter. As luck would have it, the temperature at which most of the enzymes are optimally active, except for lipase, is right around the same temperature that kills the yeast.

My idea is to take a quantity of the rice and the same quantity of the nuruk and water proportional to the recipe and mash it like beer at around the same temperature range of malted barley. This should result in killing off the yeast so no alcohol conversion occurs during mashing and would allow the enzymes in the nuruk to work on the rice. Once that mashing cycle is complete we can have our original gravity (OG).

The only potential issue I see with this is that during the fermentation of the makgeolli, the temperature doesn't (or shouldn't) get anywhere near that of the 140+F range and therefore the enzymes will never be in their optimal temperature range. I'm assuming this would definitely affect the amount of starches being converted to sugars. The only other way I can think to compensate for this would be to bring the mash up to a temperature around 150F to kill off the yeast then bring it down to perhaps the upper range of fermentation temps, say 80F and hold it there for... well, not sure.

Anyone who thinks I'm on to something or completely crazy, please let me know. I think it might just be crazy enough to work.

 

[MackerelQ]

I had one more idea on this. What if I combined a small portion of the nuruk and the equivalent amount of water in a sterilized jar and heated it up to about 150F to kill the yeast, cooled it down to fermenting temp then added the rice. I would keep this sealed and at fermenting temp for the same duration of the brew. At bottling time, I’d filter and get the gravity of the non-fermented brew which sat at the same temp for the same time and therefore had the opportunity to have the same enzymatic action on the rice.

Might work too... if it doesn’t rot with no alcohol in it.