The PA scale

I never really got used to the BRIX numbers.... but appreciated the specific gravity scale better: 1.090, etc. but even better than that is just to look at PA - "potential alcohol." and say: hmmmm, this is what I"m gonna be close to. it's worked for me so far...12-14%.....that range

Hi Rick

Yup - Most folks do it that way, and so do I. With pre-pitch readings and calculations, everything works out just fine. It is only the post-pitch readings that get messed up. Thanks for your answer.

Frederick

PA scale is an indication of where you might end up. You still have to calculate where you actually ended up when the fermentation is over.

Ray

PA is Potential Alcohol, an estimate of the alochol content if all of the sugar is consumed. If any sugar is left in the must, you will not reach this potential.

Andy

I am very serious about this question. I can site references that state differently that what you say. Can you give me accepted, published references that agree with your statement?

Ray

Ray & Andy,

One mole of sugar produces 2 moles of alcohol. The molecular weight of sugar is 180 and the molecular weight of ethanol is 46. So theoretically,

180 grams of sugar can produce 92 grams of alcohol. 92 divided by 180 is .511 or 51.1 percent.

But in practical fermentations, only 90 - 92 percent of the sugar produces ethanol. The rest of the sugar produces higher alcohols, acetaldehyde, succinic acid, etc.

In addition, some alcohol is blown off by the escaping carbon dioxide gas.

See Margalit, "Concepts in Wine Chemistry," page 56.

Regards, lum

Thanks Lum but that is not what I am looking for. I know all that. I can calculate the theoretical, maximum yield but I want the practical yield. What I really am looking for is published raw data on beginning and ending SG (or equivalent) and actual measured alcohol in the finished wine using a laboratory determination rather than charts. I am embroiled in a dispute with certain parties as a result of the article on determining alcohol that I published in WineMaker. I have good references to accepted publications that that state what the tables that are but I have not found raw data that really verifies their tables and how they should be used. I have tried to get this type of information from a number of laboratories that should have it but have not been successful. (I am not willing to pay for it, that is why I want published numbers.) If anyone can come up the this type of information I would be really grateful.

Ray

Ray,

I have not followed this discussion, so please pardon my ignorance.

I hope the following data is of interest to you.

Starting Finished Brix Brix Alc. 1 Alc. 2 Alc. 3

24.3 -1.6 13.0 13.2 12.6 24.1 -1.4 13.1 - 12.8 22.8 -1.7 12.4 - - 23.5 -1.5 12.4 12.7 - 25.1 -1.3 13.6 13.7 - 23.2 -1.5 12.3 12.4 12.2

These data from a few wines made in my garage over the past few years. All are red fermentations done in !/2 ton fruit bins without temperature control. The time from starting Brix to finished Brix is 7 to 10 days, except for the 25.1 Brix fermentation. It was hot and fast and finished in

5 days.

The first column is the starting Brix. The second column is finished Brix. The third column is the alcohol measured by my home made ebulliometer. The fourth column is the alcohol measured by a well calibrated commercial ebulliometer. The fifth column is the alcohol measured by a standard distillation method.

Regards, Lum Del Mar, California, USA

Ray A good library will have Polarimetry, Saccarimetry and the Sugars by Bates, NBS Circular C440. It's out of print, a 1942 publication. NIST still uses it. It is a definitive text but it's pretty deep. If your regular library does not have it, try a nearby college. (We have several copies here in Pittsburgh, NIST recommended the book to me a few years ago when I had similar questions and I had a hard time finding it; once I found one copy a few other sources became obvious.)

I have a copy and can email you an excel spreadsheet with values taken from the book, but the bottom line is outside influences make prediction of alcohol content an approximation only. They used standardzed sucrose solutions for the values, not juice. I corrected the tables for the changes in our understanding of mass and volume; they are miniscule, but I did it anyway.

Lum, I have though about making my own ebulliometer since they are so pricey. I have a good RTD somewhere, how hard was it to make the boiling chamber? I was wondering if I could just use a boiling flask and stopper. Could you share your setup and tables? Regards, Joe

Joe Sallustio wrote"Lum, I have though about making my own ebulliometer since they are so pricey. I have a good RTD somewhere, how hard was it to make the boiling chamber? I was wondering if I could just use a boiling flask and stopper. Could you share your setup and tables? Regards, Joe"

Same from me Lum. I bought the thermometer several years ago and tried to rig up a home made ebulliometer but never trusted the test results.

Bill Frazier Olathe, Kansas USA

Joe & Bill,

I made my ebulliometer over 40 years ago, so I can't give you many details. At that time, I was working for NBS and had access to great machine and welding shops. I borrowed a commercial ebulliometer (from a local winery) and essentially duplicated it.

For calibration, I made up known alcohol solutions from absolute ethyl alcohol and I also checked against the commercial ebulliometer. Calibration can also be done with H2O if you measure and correct for the atmospheric pressure. (You do this kind of calibration each time you use the ebulliometer). A good thermometer, complete condenser reflux and minimum temperature gradients seem to be important issues.

I am currently using the ebulliometer chart in "Making Good Wine" by Bryce Rankine, page 331.

I don't think people understand the difficulties in accurately measuring the alcohol content of wine. Dissolved solids (sugar, acid, etc.), changes in atmospheric pressure (4 mm = 0.5%), small temperature changes (0.02 degrees = 0.1%), etc., etc. cause significant errors. The difference between 12 % and 12.5 % is only FOUR PERCENT and accurately measuring alcohol (or anything else) to 4 % in such a complex solution as wine is tough.

Regards, Lum Del Mar, California, USA

Well, next time I'm up Presque Isle I'll ask them show me one. I fully appreciate your comments on accuracy and share them. I was always told water boiled at 212F in school. After working in a standards lab for years I found water usually boiled at 210 F here in Pittburgh, our barometric pressue is usually around 740 mmHg, not 760 mmHg. I understand reflux condensers and once I see one I think I can duplicate it. Bill, if it looks doable I will be in touch. Regards, Joe

Thanks Lum. I will see what I can do with your data. Also, thanks to Joe, I will try to track down your reference.

Ray

Ar a recent talk, a professional winemaker here from BC mentioned that they were getting higher alcohol levels for the starting Brix than they used to, often by 1% or even more. She said this was confirmed by other winemakers from the area. Her hypothesis was that the yeast were getting more efficient in alcohol production. This could have large repercussions if that were indeed the case. I'm wondering if this is happening in other, hotter areas, as well?

Pp Vancouver, Canada

theoretically,

Some types of wine yeast produce more alcohol than others, so the above situation certainly seems possible. But, I don't understand what the "large repercussions" would be. Lum Del Mar, California, USA

Well, if the yeast got consistenly more efficient in producing alcohol, then the winemaking practice would have to adjust to that somehow, particularly in hot areas, otherwise we'd end up with hot, unbalanced wines, no? 1% is a lot as an average change.

I believe she's been using the same yeast over the years, so it's not a change in the type of yeast.

Pp Vancouver, BC, Canada

Going from 12 to 13 percent alcohol would indeed change the general character of many wines, but making well balanced, high alcohol wines is not necessarily difficult. Going from 13.1 to 14.1 percent alcohol results in a big change in the tax due on commercial wine made in the USA. Of course, the winemaker can control the alcohol content of the finished wine to some extent by adjusting the starting Brix (one way or another).

If she has been propagating her own yeast for many years, I would suspect the yeast has changed. On the other hand, if she is using dry yeast, then I suspect the additional alcohol is due to some factor other than yeast.

Regards, Lum Del Mar, California, USA

Could you locate contact information, name, or whatever, for the person giving the talk. If you can, you could pass it to me directly at my email rather than putting it on the news group. (They may or may not appreciate that.)

Ray

theoretically,

Hi Pp

I suspect that this is nothing more than another case of _misapplying_ that same old end alcohol formula that pops up every now and then. Using this formula will _always_ produce answers that are 1-2%abv

*too high* !! Let me give an example of this:

We start a ferment with an OG of 1.090 (22BRIX/12PA). We ferment it down to an EG of 0.990. If we then use that end alcohol formula, it will _try_ to tell us that we have 13.4%ABV in our wine, which of course is wrong.

Earlier in this thread, Andy gave us a definition of PA: "...PA is Potential Alcohol, an estimate of the alcohol content if all of the sugar is consumed. If any sugar is left in the must, you will not reach this potential..."

Thus - Our original PA was 12. All of the sugar is consumed in producing that 12%ABV. With no more sugar to consume, our ferment comes to a halt, and there is _no way_ we can reach

13.4%ABV in that wine.

It's all very simple. Really !! Tell that lady she hasn't discovered a mutated strain of yeast, she is only MISapplying that method of determining end alcohol. If she doubts this, she can easily pay a lab to test the wine to be sure. HTH

Frederick