Starting Brix, ABV, and Residual Sugar: How linear?

Here’s a winemaking question:
On wine.woot there is a Bell wine with the following stats:

Petit Verdot 2006 Massa Ranch, Yountville, Napa Valley:

Technical Analysis
Varietal: Petit verdot (99%)
Cabernet sauvignon (1%)
Source: Massa Ranch, Yountville, Napa Valley
Harvest Date: October 31, 2006
Harvest Sugar 26.2 Brix
Harvest Acid 0.83 gm/100ml
Acid 0.64 gm/100ml
pH 3.75
Alcohol 13.6%

My major question is with that starting brix and that ending ABV, is it really likely that the wine has been fermented fully dry? How much linearity is there between starting brix and ending ABV assuming fully dry fermentation. Does it vary by grape somehow? And how accurate/consistent are reported residual sugar stats(sucrose and fructose versus total), PH stats, and total acidity stats?

Stats for the other wine listed:
2005 Bell Wine Cellars Merlot, Yountville, Napa Valley:

Varietal: Merlot (98%) Cabernet sauvignon (2%)
Appellation: Yountville, Napa Valley
Harvest Sugar 24 Brix
Harvest Acid 0.54 gm/100ml
Total Acid 0.63 gm/100ml
pH 3.59
Alcohol 13.7%

Same ABV with moderately higher brix?

For brix to alc., use 0.6 as a multiplier. My guess for the first wine is some added Jesus units to get the alc. down before fermentation.

Love them numbers!!!

As Kris stated, there most likely was some ‘manipulation’ done at some point, either via a water add or reverse osmosis.

The general consensus on conversion is somewhere between .57 and .60 times the brix (give or take a bit because of ‘fermentable vs. non-fermentable’ sugars). If this is the case, and no alterations had taken place, we’d seen an alcohol level somewhere between about 15.0 and 15.5 % . . . and as you can see, that’s a very wide margin. I would guess it to be on the higher side.

I’m sure others will pipe in . . .


My guess:

The first wine had a water add, which would explain the lower alcohol and possibly the acid drop from harvest to bottle (though yeast choice and MLF could entirely explain the acid drop also).

The second wine had only an acid add, but no water, so it has the same ABV as the first wine, but the acid went up from harvest to bottle.

OK, makes sense. Any idea:

  1. What percentage of higher end CA winemakers add water. I didn’t realize it was prevalent toward the higher end of the scale. Mainly to keep ABV in check I presume.
  2. What % of higher end CA winemakers add acidity. Some have told me they do and have suggested it adds to the ageability of their wines.
  3. Do many CA winemakers use their ABV tolerance in the most favorable manner possible tward showing lower than actual ABV.
  1. 35.6 %
  2. 47.3 %
  3. 74.6%

Just rounding, of course . . . . (-:

In all seriousness, this is something you will simply never know for wineries do not need to disclose this - and based on some thoughts on these boards and others, they would be tarred and feathered should they disclose the truth . . .

It is very common to do water and/or acid adds, and the government certainly allows such adds. In a year like this, where Mother Nature did not allow for brix levels to climb to the levels they usually do, you’ll hear a lot of winemakers tout that they did NOT add any water, but this was a very atypical year . . .


Larry – What about differences in yeasts? A couple of years ago there was a lot of discussion about some yeasts producing more alcohol for a given amount of alcohol. Obviously there’s a chemical limit to the conversion rate, but how much difference is there in yeast “efficiency”?

  1. When the brix are too high, all of them. (or use RO later, which is a nastier word)

  2. When the acid is too low, all of them.

  3. When the ABV puts them in a different tax bracket, >14.5%, and they can legally fudge 1%, alot of them.

These things happen all over the world.

It seems to be more or less the norm, though not universal. I was surprised to hear Mick Unti at Unti Vineyards in Dry Creek say a couple of years ago that they routinely water back. Their wines don’t have late-picked flavors and he’s plainly aiming for a relatively restrained style, so I didn’t expect they’d feel the need to pick at such high sugars that they’d need to add water. But they do.


There will always be talk about yeast efficiencies - and these will always be somewhat of a moving target. ‘Starting Brix’ is a moving target as well, for it is not that easy to get a really ‘precise’ starting figure. Some send samples off to third party labs that provide them with ‘fermentable sugar’ numbers and anticipated alc levels based on yeast conversions, but these are not entirely ‘precise’ either . . .

I’m sure that some will jump on this thread with exact, precise numbers . . . based on their own ferments, which is certainly an interesting subset . . . but is it possible to extrapolate this data and apply it to the whole?!?!?

We use about .58 as our ‘anticipated’ conversion rate . . . but truly have no precise idea about exact alc levels until after primary and secondary fermentations are complete - and until after elevage is complete as well.


Thanks, Larry. I remember a winemaker posting on eBob a few years ago suggesting that the supposed differences in yeast efficiencies were actually just a reflection of the problem measuring Brix accurately.


I remember that thread as well . . . .

I don’t want to minimize the differences because I think that they are real - and as more and more yeasts are cultivated from specific fermentations and regions, we’re bound to ‘crack the code’ at some point and truly have real differences . . .

And hopefully folks don’t poo poo this concept - no different then hand selecting rootstock/clone combos to get what you want with your grapes - with all of this possible because of the same types of research.


That was probably me [berserker.gif]. In fact, you can’t make any valid conclusions from the numbers presented in the 2 examples. It’s virtually impossible to know for sure what the real starting brix level is, and the ABV on the label isn’t always accurate.

Indeed, it was you, Brian. Thanks.