Does anyone know how commercial wineries calculate the ABV %. We all know in the home made world we just use a hydrometer to give us an estimate of what the wine could be when dry but I am fairly confident that the government holds commercial wineries to higher standards than just guessing and they must have an accurate way of measuring it because how would they come up with 12.1%, 12.3% etc.... Is there a piece of equipment that measures alcohol percentage after fermentation??
Precise calculation for ABV %????????
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I don't know about commercial establishments that may have very expensive equipment, but this equation works: ((SG-FG)*0.42)/100 = ABV, where SG/FG are starting/final gravity. (Note: this equation is intended for degrees Plato. If you are using specific gravity, the conversion is this: ((-205.347)*(SG*SG))+(668.72*SG)-463.37 = Plato, where SG=specific gravity.)
Guess I'm a little confused by the question. Not sure how you've been doing it, but I always take a gravity reading of the must at the beginning and the end. Those two numbers are used to calculate the ABV. I never estimate how much alcohol COULD be in my wine. I know that number with certainty.
I guess what Im saying is: Are hydrometers really accurate enough to precisely calculate the ABV? I don't think so. Obviously you can take the Original gravity and the end gravity to get fairly close to the ABV but coming up with a digital number like 12.3 from an analog device seems rather inaccurate to me. Maybe I am being a bit too picky lol.
So my knee jerk reaction here was to respectfully disagree that hydrometers aren't accurate enough to precisely calculate ABV. Going on my own experience (I spent a lot of time in the lab while in college), many of the analog devices we used were only limited by the ability of the user to read them accurately. Also, we have yet to define "precise" in this thread. If we want to calculate ABV out to the 10th decimal place, it probably wouldn't be accurate enough. However, a single decimal place, as labeled on all wine and beer bottles. seemed like a reasonable goal for the meager hydrometer.
But, I wanted to make sure I didn't throw around unfounded claims with no solid evidence to support them. Therefore I did some quick Googling research. In a matter of seconds I came across this hydrometer with a resolution of 0.0005.
http://www.northernbrewer.com/shop/lab-grade-hydrometer-1-000-1-070.html
A hydrometer like this would give results that would allow you to take your ABV calculation out a few more decimal places if you so desire. This also confirms my understanding that many people own multiple hydrometers with a variety of ranges on them. Utilizing a specialized hydrometer for a specific range you get the most accurate readings.
Back to your original question, I still don't know what the commercial folks use. But, I would wager that even if they use some fancy and expensive lab equipment you could get a comparable result with a good calibrated hydrometer.
So in conclusion, assuming we're only shooting for the same accuracy that commercial producers advertise, I still respectfully disagree that a hydrometer isn't accurate enough.
This has been educational. Thanks for asking the question and prompting me to do some research!
Thanks for the information, You also have to factor in the temperature compensation as well and figure that during that adjustment you aren't going to be 100% accurate. I just got a refractometer and have been playing around with it a bit lately but I am mainly going to be using it for measuring brix on grapes for harvest time. I know this isn't entirely accurate either and a lot of wine makers don't even use refractometers they simply go by taste alone. Kind of off topic but I guess since we are talking about instruments I figured I would include this aswell. Again thanks for the response.
I found this equation to be similar to the one above but a lot easier for me too understand. I edited it a bit for temperature compensation.
1. OG+-temp compensation number- FG+-temperature compensation number = TG (Terminal Gravity)
2. TG x 105 = % Alcohol by weight (a.b.w.)
3. a.b.w. x 1.25= % Alcohol by volume (a.b.v.)
I found this equation to be similar to the one above but a lot easier for me too understand. I edited it a bit for temperature compensation.
1. OG+-temp compensation number- FG+-temperature compensation number = TG (Terminal Gravity)
2. TG x 105 = % Alcohol by weight (a.b.w.)
3. a.b.w. x 1.25= % Alcohol by volume (a.b.v.)
Ah yes! But taking a measurement at a temperature other that 60F would be user error, not a fault in the instrument or calculation.
