So how much alcohol is REALLY in my wine?

[balatonwine]

Look at it from a different POV -- yeast is big money.
...

US grape production (not wine production) is valued at $6.5 billion USD.

As are other crops, which are actually easier to grow. I have been upping my lettuce volumnes in the past few years..... Global trend. And I do not even now live in the USA.

"The US lettuce and chicory market is forecasted to reach US$5.09 billion in 2026"

Source: US Lettuce & Chicory Market Report (By Type, Exports & Imports): 2022 Edition

 

[BigDaveK]

Okay, but now you know that your initial premise was false. Our yeasties do make alcohol, even in an aerobic environment.

Whaaaaaaatttt?
Not exactly.
I said under aerobic conditions they need the sugar and oxygen to multiply. The oxygen is needed for the production of lipids and nicotinamide adenine dinucleotide. In an anaerobic environment - no oxygen - they're forced to make ethanol. That's all basic stuff from Day 1 at Wine Camp. I admit my original premise was incomplete. It won't happen again. I actually appreciate your pointing that out and reminding me. I have too much new stuff in short term memory and it can easily get lost.

And seriously - I've had a couple ferments drop 40 points in 2 days. How much of that sugar was only used for multiplication? I don't know! Worse case that could be a 5% change in ABV. Considerable!

I'm retired so an ebulliometer won't be an addition to my wish list. It would be easier to give a sample to Jo-Jo at the tavern - she has a gift.

 

[BigDaveK]

I laughed when I saw it, because when I read the OP I was thinking how many rabbit holes does @BigDaveK have in his backyard? He was in one last week and now he has his foot caught in another!

Fortunately I only have one rabbit hole for wine making. Unfortunately it behaves like a sink hole. Surely it has to stop growing someday. Doesn't it? Maybe? I hope!

 

[Raptor99]

The other reference was saved as a PDF and I don't have a link. It's really interesting.

Yeast Life Span and its impact on Food Fermentations - Aranda, Orozco, Picazo, Matallana

https://www.researchgate.net/public...ife_Span_and_its_Impact_on_Food_Fermentations

 

[Raptor99]

If you look at the chart in the above article, you see that ethanol does increase during the exponential growth phase. In fact, it looks like about 1/3 of the total ethanol production takes place before the anaerobic stationary phase. But by that point, more than half of the sugar has been consumed. So I think we can safely assume that some of the sugar is used for cell growth rather than ethanol production. If we were able to study the numbers underlying this graph we might be able to make some calculations. The question is whether any of the ABV calculators take this into account.

 

[barryjo]

Been thinking about this...

Specific gravity measures the density of the wine. Early on the SP goes down because the sugar is being consumed by the yeast. Under aerobic conditions - the bucket - yeast use the sugar for multiplying and they give off CO2. They don't start ethanol production until they're in an anaerobic environment - the carboy with airlock. So it seems to me going by the change in SG gives a VERY approximate ABV at best. Am I wrong?

I transfer to secondary between 1.020-1.030. Seems to me you want anaerobic conditions early while there's still food for the yeast to function and make a boatload of ethanol. Again, am I wrong? And is there an easy (meaning inexpensive) way to measure alcohol content?

I'm wondering if the older recipes that go under airlock from the start were on to something?

Since CO2 is heavier that air, won't that protect the wine from oxygen? Until fermentation is finished and the CO2 dissapates? I never put wine or beer under airlock until strong acticity ceases.

 

[Ohio Bob]

Since CO2 is heavier that air, won't that protect the wine from oxygen? Until fermentation is finished and the CO2 dissapates? I never put wine or beer under airlock until strong acticity ceases.

Yes and no. CO2 does protect the wine, but it mixes with oxygen. Otherwise we’d all be dead, breathing nothing but CO2. When wine ferments and produces CO2 in quantities to outnumber oxygen, it’s a great protector.

 

[sour_grapes]

Whaaaaaaatttt?
Not exactly.
I said under aerobic conditions they need the sugar and oxygen to multiply. The oxygen is needed for the production of lipids and nicotinamide adenine dinucleotide.

You also said

They don't start ethanol production until they're in an anaerobic environment - the carboy with airlock

 

[BigDaveK]

Since CO2 is heavier that air, won't that protect the wine from oxygen? Until fermentation is finished and the CO2 dissapates? I never put wine or beer under airlock until strong acticity ceases.

To expand a little on what @Ohio Bob said, there are also a lot of variables involved - temperature of the must, hard cap or foam, the breeze from a ceiling fan.
It's also possible to have too much CO2. I've read concentrations above 40% start to affect the yeast. That's one of the reasons we stir the must. Even a gentle stir releases a lot of excess gas.

Oh oh! Just had a thought - How long before the woke crowd comes after us for releasing greenhouse gasses?

 

[BigDaveK]

You also said

Yes, and I also thanked you for reminding me about the Crabtree Effect. If you want to say I was wrong, that's fine. I'll survive.

 

[winemaker81]

It's also possible to have too much CO2. I've read concentrations above 40% start to affect the yeast. That's one of the reasons we stir the must. Even a gentle stir releases a lot of excess gas.

Huh. I did not know that. As I say, there's always something new to near about winemaking!

Oh oh! Just had a thought - How long before the woke crowd comes after us for releasing greenhouse gasses?

 

[sour_grapes]

Yes, and I also thanked you for reminding me about the Crabtree Effect. If you want to say I was wrong, that's fine. I'll survive.

Okay, good. Text is hard. I got the impression from your "Whaaaaaaatttt? Not exactly" comment that you thought I had mischaracterized your posts.

 

[BigDaveK]

Huh. I did not know that. As I say, there's always something new to near about winemaking!

Apparently it can overwhelm the cytosol inside the yeast cell, changes it's pH, and interferes with enzyme activity. In fact, CJJ Berry in the 80's listed excess CO2 as a cause for stuck fermentations.

Interestingly, CO2 in the atmosphere is causing some grape varieties to produce more sugar.

Reading scientific papers is fun but eventually I reach the blahblahblah point and have to put them down,

 

[barryjo]

None of the formulas are correct. Not absolutely, anyway. They are all approximations. That is why Fermcalc gives you four or five to choose from. But, they are all within 1% of each other, so they are close enough for me.

As pointed out above by @balatonwine the only accurate measure is by a lab or use an ebulliometer.

Out of the Fermcalc methods, I much prefer the Honneyman method. I print out the conversion table and the rest is easy. (I prefer easy!) According to the author, this method is very close to the ebulliometer method. And last I checked, ebulliomenters ran about $700. And I obviously hadn't checked lately. Some going for #1300.

 

[BernardSmith]

I guess the unexplicated assumption is that SG converted into ABV does not assume that there is any loss of sugar because of the yeast's other uses of the sugar, but the calculations to convert FG-SG X 131.25 may very well account for the accurate measures of alcohol in solution. Where does that 131.25 figure come from? and is it less accurate or more accurate as the difference between FG and SG gets greater or smaller?
Oh... and as to "woke" crowds - and I wonder why that term is always used by those on the right to disparage what we understand about civility and science -and if you are not on the right, perhaps not use that term - even as an ironic joke. It ain't funny and it ain't collegial. Thank you.- your average cow farts or belches about 220 lbs of methane every year. You as a home wine maker would need to be producing wine that started as about 35,200 lbs of fermentable sugar annually to produce that amount of CO2 to compete with ONE cow...given that methane is 80 times more powerful a problem than CO2 AND that yeast convert about 50% of the sugar into ethanol and not CO2.

 

[BigDaveK]

Over the weekend I started possibly my most unusual wine yet. (More on that when I transfer in 5-6 days.) It has no sugar and yet the must prior to sugar addition was 1.026. Clearly my "juice" is dense. IF that were sugar and IF it fermented to .990 we/re looking at an ABV of roughly 4.6%. That's a considerable portion of the final ABV.

After sugar my OG was 1.090. I'm thinking about adding more sugar.

 

[David Violante]

Dave, now I'm down a rabbit hole... LOL

I found several other methods of determining sugar concentration aside from using a refractometer or hydrometer. None appear as fast and easy though, as @balatonwine indicated previously.

Radio Frequency Sensing​

Light Polarization​

Laser Pointer and Prism​

...and there are 124 listed methods at the International Commission for Uniform Measurements of Sugar Analysis website.

These are interesting questions; how much sugar is actually used by yeast as compared to how much is converted to alcohol; and, are the instruments we are using to measure sugar content actually measuring sugar content and not additional things (confounding factors). I'm quite happy to continue using my refractometer and hydrometer to get as close as possible, for what I'm doing and how much I'm making. I'm also looking forward to seeing what is on the other side of this research! For example, we use light spectrometry to determine oxygen concentration of blood (pulse oximetry). The more oxygen, the brighter the color. Concentrations can be measured and compared to a standard to give a number. Measuring Sugar Color seems to be quite similar.

 

[Raptor99]

One thing we learned in beginning chemistry is that every measurement is an approximation, which can be expressed at +/- the margin of error. All we need is a measurement that is accurate enough for our purposes. So a tape measure is good enough for most household projects, but for some engineering projects you might need an extremely accurate micrometer. Even if I had a micrometer, I would not use it for building a workbench. I suppose that the only 100% accurate measurement of sugar would be to find a way to count the sugar molecules.

However, this rabbit hole is interesting. It appeals to my inner nerd.

 

[BigDaveK]

Dave, now I'm down a rabbit hole... LOL

And that's not a bad thing!
I like to think that knowing the mechanics might possibly improve our skills at least a little bit.

Clearly some of the sugar is dedicated to reproduction. How much? Don't know yet.

And to throw another wrinkle in the mix - we make the assumption that only sugar is responsible for dissolved solids affecting must density, the specific gravity in other words. My message #36 shows a considerable increase in SG with no sugar. I suspect all flavor ingredients have dissolved non-sugar solids, some negligible but some perhaps considerable, further reducing the expected ABV.

Hypothetical situation - what if I accidentally make a low alcohol wine around 11% ABV? What if the actual ABV is 3-4% lower? That exposes me to a number of wine faults that I thought I was insulated from. I like using the simple formulas for calculating approximate ABV but there has to be faith that the number is at least in the ballpark.

 

[balatonwine]

One thing we learned in beginning chemistry is that every measurement is an approximation

My first year college chemistry professor like to tell a story. When he was working his way through college. He did titrations as a job. And he only did one. Why? He said if he did two, the second one was always just a little different. So if he did two, he had to do three to prove his first one was accurate.

I never was sure if he was kidding or serious.....

Years later, as I got quite a bucket load of graduate level statistic courses under my belt, I kind of got his point (joke...?).

That being said..... even if without any stats under your belt, the old experienced carpenters rule works for a reason: Measure twice*, cut once.

* Darn if if he was not right... If I do carpentry, I tend to always still measure 3 times..... Just to make sure.