SG of bone dry wines

[Rappatuz]

I wanted to calculate the concentration of sugar in my recently bottled wild strawberry wine. Not the back sweetened amount - the total amount of sugar per liter. I did some searching and found several sites displaying tables with SG's for different percentages of ethanol in water (by weight). Here's a selection of values from one of the tables (at 20 C / 68 F):

ABW (%) from source	ABV (%) derived from source ABW values	SG from source
7	8.9	0.986
8	10.1	0.985
9	11.4	0.983
10	12.7	0.982
11	13.9	0.980
12	15.2	0.979
13	16.5	0.978
14	17.7	0.976
15	19.0	0.975
16	20.3	0.974
17	21.5	0.973

This tells me that a "bone dry" wine that finished at 0.990 really isn't that bone dry after all. If its ABV is 11 %, then 18 g/l sugar should still remain in the wine, according to the above presented data.

This sounds a little weird, and I question myself if it can be correct. Some commercial wines contain 1 g/l sugar, or less. Do they really ferment that low, or is my logic in some way flawed?

 

[sour_grapes]

I will be honest -- I cannot quite follow your example. However, what I think is going on is that your logic and calculations could be correct -- but they assume that the only things in the wine are water, alcohol, and sugar. But there are other dissolved solids in wine: tannins, flavor molecules, color molecules, proteins, glycerine, etc.

Can you provide a link to your source material?

 

[Rappatuz]

I will be honest -- I cannot quite follow your example. However, what I think is going on is that your logic and calculations could be correct -- but they assume that the only things in the wine are water, alcohol, and sugar. But there are other dissolved solids in wine: tannins, flavor molecules, color molecules, proteins, glycerine, etc.

Can you provide a link to your source material?

Yes, I forgot to state that my assumption is that only sugar and ethanol will have an appreciable effect on measured SG. I realize that this assumption may be wrong. Hopefully, people with more knowledge about this subject will give us some answers.

Here's a link to the table where I got my data:
S.G. Table for Ethanol-Water

 

[Rice_Guy]

There is a crop number which is called sugar free dry extract which should be attached to every juice, ,,, the SFDE influences what the hydrometer reads, ,,, example my hydrometer lab calibration method has me take distilled water and mix salt to accomplish several known density numbers to “calibrate” the tool.

The conversion table of hydrometer reading sitting in grape juice into percentage sugar is an average “theoretical” sugar from numbers collected over several years and several growing regions which was measured in a chemistry lab. Sugar is not consistent! ,,. The grams per liter SFDE will vary slightly every season and every growing region. Common examples are a cool year or picking early cause your anxious or a cool costal area has low sugar therefore the SFDE will be higher. Picking later or some varieties or grapes from the Central Valley will have higher percentage sugar therefore lower SFDE.

To complicate the world more the calibration table for apple juice/ other crops is different than the appropriate table for grape juice, ,,, the sugar free dry extract is crop specific.

In the scheme of things the hydrometer test is easy/ low cost/ reproducible and known error is good enough for alcohol calculations, ,,,, or buying commercial juice for a factory.

 

[Rappatuz]

There is a crop number which is called sugar free dry extract which should be attached to every juice, ,,, the SFDE influences what the hydrometer reads, ,,, example my hydrometer lab calibration method has me take distilled water and mix salt to accomplish several known density numbers to “calibrate” the tool.

The conversion table of hydrometer reading sitting in grape juice into percentage sugar is an average “theoretical” sugar from numbers collected over several years and several growing regions which was measured in a chemistry lab. Sugar is not consistent! ,,. The grams per liter SFDE will vary slightly every season and every growing region. Common examples are a cool year or picking early cause your anxious or a cool costal area has low sugar therefore the SFDE will be higher. Picking later or some varieties or grapes from the Central Valley will have higher percentage sugar therefore lower SFDE.

To complicate the world more the calibration table for apple juice/ other crops is different than the appropriate table for grape juice, ,,, the sugar free dry extract is crop specific.

In the scheme of things the hydrometer test is easy/ low cost/ reproducible and known error is good enough for alcohol calculations, ,,,, or buying commercial juice for a factory.

Thank you for bringing more insight into this subject.

If I understand you correctly, the SG value that represents "no sugar" will vary for different kinds of juices/wine types, even when ABV is kept constant. This means that "other stuff" also have an appreciable effect on measured SG and that my initial assumption was incorrect.

Following your logic, to be able to measure the sugar concentration in a wine with a hydrometer, we'd need to know what the "no sugar SG" is for that particular type of wine. I'm sure that the fact that we use different ratios of fruit mass per volume unit further complicates this issue.

 

[Rice_Guy]

YUP, the food world is complicated and I know a gravity number is only close, but we will continue to use gravity since it is easy.
by “no sugar” I translate that to be saying “a dry wine”. Yes the other stuff can have some to even an appreciable influence. My best reference Cider Maker Handbook notes:
alcoholvolume = K times (change in SG)
Constant K wraps in dry solids/ salts/ proteins/ acids/ non-fermentable reducing sugars. K is expected to vary from 125 to 130 with ciders and in their example calculation the cider could have an alcohol of 6.5% to 6.76%, ,,, for US product labels 0.5% error is accurate enough so folks just use gravity, (Grape and beer have a K up to 136). If you determine K for one lot of wine, well you also know that it would need to be tweaked depending on pick date/ wet rainy year/ old vines/ etc. How about pressing method for the juice, ,,, example I have a data set on cooked beets vs freeze then press beet juice, the gravity was off by 0.003 pH by 0.2 and the TA probably experimental error so it wasn’t visible. . . . Do we add pectase? it is a nice viscous molecule . . . .

Your original post was calculating residual sugar. To this I ask why? To measure sweetness? fructose is sweeter than sucrose and glucose and we have not even gotten into weird non-fermentables which will add body/ legs but not much sweetness, ,, and our ability to ”taste” sweet seems to be a log of concentration function and is compromised by other molecules which are in the soup (ex olive oil in a recipe).
From a FDA label if I want a sugar number a beverage sample would go to a lab which would run Fellings reducing sugars, or possibly HPLC,,,, and if it is an existing crop USDA handbook 8 was good enough.
Your bone dry 11% ABV should have 1 to 1.5% sugar with the lab test which the average Saccharomyces can not metabolize ,,, and in the scheme of things you might not metabolize either, ,,, so yup the world of chemical make up is complicated

If I understand you correctly, the SG value that represents "no sugar" will vary for different kinds of juices/wine types, even when ABV is kept constant. This means that "other stuff" also have an appreciable effect on measured SG and that my initial assumption was incorrect.

Following your logic, to be able to measure the sugar concentration in a wine with a hydrometer, we'd need to know what the "no sugar SG" is for that particular type of wine. I'm sure that the fact that we use different ratios of fruit mass per volume unit further complicates this issue.

 

[Rappatuz]

Your original post was calculating residual sugar. To this I ask why?

Great info!

If there was a practical way to measure/calculate total sugar concentrations in wines, then I could include that information on labels. It would also be interesting to compare sugar concentrations of different wines I make.

Taste isn't only affected by the back sweetened sugar amount - residual sugar may also contribute to the taste.

 

[Rice_Guy]

yes there are several chemicals that contribute to sweet ,,,,,, i doubt that 1% residual sugar has much flavor impact

label info,,, why?,,, we are working in industry to simply get folks to look at the calorie density of foods when they eat and folks since the 1930 have been exposed to the concept of calories per gram. oh of course you could use the label to educate folks about the food pyramid.

 

[winemaker81]

i doubt that 1% residual sugar has much flavor impact

I backsweeten very lightly. 1% sugar makes a tremendous difference in flavor.

label info,,, why?

Because I want it. Seriously. I'm not concerned about nutrition. I want to put the residual sugar on my label because I want it there. No one is going to not drink the wine because of the percentage sugar.

Don't take this negatively, as it's not meant that way. You are in the food industry and it colors how you view things. Those of us not in the industry may look at things very differently.