Residual Sugar; grams/liter or %

Grams per Liter is how I have always understood RS.... As to the 1.7 conversion factor.... it's news to me.... would'nt it be a .75 conversion, to get the actual amount of RS in a 750 ml bottle? or am I missing the point completely?

cheers Mathew

Typically, in the USA, RS is expressed as grams per 100 ml, or degrees brix. Degrees brix is another way of saying grams of sucrose per 100 grams of solution. To express brix as weight/volume percent, one needs to know the density of the solution. This can be gleaned from specific gravity measurement. However, since brix measurements are readily convertible to specific gravity measurement using a conversion table, one need really only know one or the other, and the temperature at which the measurement was taken, as long as one has a conversion table.

Craig Winchell GAN EDEN Wines

FWIW, I've never seen the term brix applied to wine itself. Grape juice yes, but not wine.

This has always been my understanding.

This term (weight/volume percent) sounds fishy to me. Weight/volume must be expressed in some units, e.g. grams/liter, and stands on its own. Adding "percent" to it makes no sense. Something expressed as percent is a ratio and is unitless, although one must ensure that that the units used to calculate the ratio are identical.

Sorry, but you lost me in all that. Again, you are using the term brix, which I have heretofore assumed was used only for grape juice, not wine itself. In grape juice, the solvent is almost entirely water and my guess is that little accuracy is sacrificed by assuming that it is all water and you seem to be suggesting that the conversion table you refer to indeed makes this assumption. When one gets to wine, however, other liquids, e.g. alcohol, with different densities come into play and assumptions that were valid with grape juice may no longer be valid.

If any of this appears to be argumentative, it is not intended to be. I'm just trying to understand something that has puzzled me for some time and that I have gotten conflicting answers on from different people.

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The answer is you're both making this more difficult than it needs to be. There is no conversion factor - no 1.7 and no .75 - it's close enough to just move the decimal. A liter of wine weighs very close to

1000 grams (or 1 kilogram, if you like), so 1 gram per liter is 1 part in 1000 or 0.1%. Sometimes you see grams per 100 milliliters (ml); a ml (a thousandth of a liter) weighs close to 1 gram and so 1 gram per 100 ml is 1 part in 100 or 1% and you don't even have to move the decimal.

- Mark W.

While you're technically correct, w/v percentages are used in chemistry. I suspect that the practice arose from work with aqueous solutions, where the density is usually close enough to 1 to render the quantity in effect unitless.

Mark Lipton

Chemistry was an incidental part of my training as an engineer and it was a long time ago. I guess I can accept that, while the term may be theoretically incorrect, it can nevertheless be useful in certain situations. In an earlier posting in this thread Mark implied that the density of wine (which is, chemically, an aqueous solution, albeit a heavenly one) is close enough to the density of water that the number for grams/liter is pretty close to being the same as that for percentage, give or take a decimal point or two. Is this what you're implying also?

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That's certainly the case with wine - SG of dry wine is typically around 0.992, so the conversion to weight/weight wouldn't change the numbers much!

- Mark W.

It's a relatively frequent occurrence with Late Harvest wines from the USA, completely allowable by the BATF and the easiest way of expressing residual sugar in the same units as sugar at harvest.

So you agree that Brix is a weight percent.

Grams per 100 ml is a weight/volume percent. Grams per liter is not the way RS is normally expressed in the USA. Whether you like it or not, those are the units used typically used, and whether you like it or not weight /volume measurements are used regularly. Why is milligrams per liter called "parts per million", when they aren't like parts? Just the way it is.

Again, not really. The only thing is that there must be a convention for it.

Even water has a density of 1 gram per cubic centimeter only at standard temp. Different sugar solutions change density at different rates with changes in temperature, and in different temperature ranges. The density of juice is far greater than the density of dry wine, and the density of sweet wine derived from that juice is somewhere in the middle of that range. Assumptions one makes concerning density of a wine are valid only for wines with similar concentrations of components.

Well, I'm a professional winemaker, so all I can say is "trust me" (grin).

Craig Winchell GAN EDEN Wines

I didn't say it doesn't happen. I just said I've never seen RS in a wine (including LH wines) expressed as brix. But I guess there's no reason it can't be. And since we agree (see below) on what brix means, our disagreement (if there is one) is over terminology, not substance.

Slightly OT: Quite a while back, a poster indicated that the only requirement for labeling a wine as LH in the USA is that the brix at harvest be shown on the label. I don't know this to be true but I've never seen anything to contradict it. Do you know if this is correct?

Absolutely!

It's not a matter of liking it or not. I'm just trying to understand it. Whether the convention is grams per liter or mg/100ml is not important, since one can easily be converted into the other by shifting the decimal point. And I still contend that "weight/volume percent" is technically incorrect, but it seems to be useful so I'll drop the issue.

I must disagree. The only "convention" that is required is that the

*type* of unit must be specified, i.e. "by volume" or "by weight", etc. Maybe this is what you meant.

I would have to agree with this, and it sort of goes to the heart of my original posting. But, in the end, are the numbers sufficiently different to be significant?

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Fodder: this is from a chemical analysis report on one of our Austrian wines (where it relates to sugar:)

reduzierende Zucker (als Invertzucker) in g/l: 224,50

zuckerfreier Extrakt (berechnet) in g/l: 50,80

Just to look at how other countries see it, e. winemonger

"Vino" skrev i melding news: snipped-for-privacy@4ax.com...

Ahem, may an European point out that a 'milli', m for short, is 1 1000th of something - so it will have to be g/l (grams per litre) or mg/ml (milligrams per millilitre) - which, of course, results in the same number for both. Anders

Never have seen that meassure, but we do not see US wines that often here in Europe.

That the way it's always given in Europe, both in technical data sheets from the labs and on labels. EU regulations regarding sweetness labelling for still and sparkling wines refer to g/l.

Very easy: 1 g/l = 0.1 percent, or 10 g/l = 1 percent.

This obviously is wrong. I am not sure, but there might be a misunderstanding: 16 to 17 grams (hence probaly the factor "1.7") of sugar ferment to 1 percent alcohol by volume.

Or, one sometimes can read of a given sauternes (Broadbent cites this in his book) counting "17 degrees, i.e. 14 + 3", this refers to 14 percent of alcohol per volume plus 3 "potential" percent of alcohol (= residual sugar), in this case ~ 50g/l or 5.0 percent.

HTH to end confusion.

M.

That the actual residual sugar (must be quite a sticky!).

And that's the sugar-free extract.

M.

Indeed! It's a Ruster Ausbruch.

-e.winemonger

After doing some checking, I'm not sure I have either. I *have* seen it as g/100ml, but only on specification sheets, which are often difficult to track down (if they exist at all). In fact I canot recall ever seeing RS provided on the label of a table wine. On the labels of things like a LH or TBA I can only recall seeing it expressed as a percent.

Strictly speaking, this is true only when the solvent has a density of

1.0 g/ml. In other words, water at standard temperature. If the solvent were, say, 0.5 g/ml then 10 g/l would be 2 percent (by weight). I guess the density of table wines is close enough to that of water that little accuracy is sacrificed by assuming they are identical. For wines with very high sugar contents, the assumption is probably less valid. Is that why RS is normally (in my experience, anyway) expressed as a percent for these wines?

After re-reading the posting I referred to, I found that I made exactly the error that you describe.

It went a long way, in any case.

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True. And it's accurate enough for labelling and general information purposes, although probably not for wine labs' analyses.

I don't think so (but I may be wrong, of course) - I fell that in the US (both on labels and in magazines) the info on RS given as a percentage is much more common and widespread. In Europe it's the other way round.

M.

In the spirit of nitpicking ;^), this isn't quite right, either - it would only be true if the density of the *solution* is 1.0 g/ml!

- Mark W.

You're right, of course. The point you make is one that occurred to me as I thought through the issue I originally raised in this thread. Another question directly related to your comment is that of how much the volume of a solvent increases when a solid, like sugar, is dissolved in it. (Of course the liquid then becomes a "solution", not just a "solvent".) For example, if I dissolve 10 grams of sugar in a liter of water, what is the volume of the resulting solution?

The practical importance of this sort of thing, when it comes to wine, is nil. But I'm the sort of person who finds these things intriquing. Perhaps you are too.

Mark Lipton, are you listening?

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