I just defrosted a pail of Gewurz juice from Columbia Gorge, WA and here are the numbers
Brix, 22.8 TA, 5.2 g/l pH 3.37
Unfortunately due to my poor planning I could not get Cote De Blanc for this and I am using Lavlin 1116 instead.
Assuming this ferments to 0.990, this is a PA of something like 13.5%
I would like to make about half dry and half off-dry and I am a little concerned about the alcohol level. Any suggestions on how to proceed?
Also, from my fruit wine making experience I always sulfite when making the starter and pitch 12-24 hours later. Is this initial dose of sulfite really necessary for healthy fruit? Is there anything wrong with waiting to add it until after alcoholic fermentation? I recall reading that sulfites prevent the yeast from metabolizing acetaldehyde to alcohol. Since acetaldehyde is a fault would it not be better to add the sulfites once the fermentation is complete?
No issue with the brix, 22.8 Brix should get you around 12.5% alcohol. The acid level, however, is too low for a white wine. I suggest double-checking the acid and then adding tartaric acid to get somewhere between 7 and 8 g/L. As far as sulfite is concerned, many juice sources add some sulfite to the juice already so you may not need to add any. A dose of 30-60ppm is "wise" in my opinion for whites. Of course, you still should adjust to 30-40ppm prior to bottling. I wouldn't be concerned about acetaldehyde, just follow good white winemaking practices. Full containers and minimal air contact after your first racking. Regarding, 1116 yeast, this is a very good clean fermenting yeast for whites.
No issue with the brix, 22.8 Brix should get you around 12.5% alcohol. The acid level, however, is too low for a white wine. I suggest double-checking the acid and then adding tartaric acid to get somewhere between 7 and 8 g/L. As far as sulfite is concerned, many juice sources add some sulfite to the juice already so you may not need to add any. A dose of 30-60ppm is "wise" in my opinion for whites. Of course, you still should adjust to 30-40ppm prior to bottling. I wouldn't be concerned about acetaldehyde, just follow good white winemaking practices. Full containers and minimal air contact after your first racking. Regarding, 1116 yeast, this is a very good clean fermenting yeast for whites.
Reasonable amounts of sulfur dioxide will not kill native yeast. It only curtails yeast activity for a few hours. On the other hand, commercial wine yeast are practically unaffected by reasonable amounts of sulfur dioxide. So, contrary to much home winemaking literature, commercial wine yeast should be added immediately following the sulfur dioxide addition. The inoculated yeast cells can then multiply quickly while the native yeast is stunned, and the inoculated yeast will dominate the native yeast throughout the fermentation period.
Sulfur dioxide is often not necessary for healthy fruit. But, by the time wine is bottled, considerable oxidation has taken place and a significant amount of acetaldehyde has accumulated. So, the additional amount of acetaldehyde produced by normal amounts of sulfur dioxide added prior to fermentation would be negligible.
Thanks for the advice. I added 0.8g/l Tartaric to bring the TA up to
6g/l and pitched last night, now I am crossing my fingers, hoping the temperature stays in the low 60's for the next week or so.
I thought I understood Brix, but maybe not. The starting SG is 1.097 which is a PA of about 12.7% alcohol. And, so far, my final SG has usually been below 1.00, usually about 0.990. Wouldn't this be a final alcohol level of about 13.7% ?
This is interesting. I will keep this in mind for future batches.
This is also interesting. It is always good to hear a reality check with respect to the dominant behavior of various practices. Basically, I just need to keep the sulfite levels at about 50ppm, adjust acid, and let the yeast do their thing.
Regarding Brix: Brix is a measure of dissolved solids in your juice, namely sugar. Theoretically, yeast will convert sugar to ethanol at a rate of about 55% so you can estimate the alcohol content of your finished DRY wine by muliplying Brix X 0.55, in your case 22.8 Brix X 0.55 = 12.5%Alcohol.
I would also suggest that you bump up your acid a bit more (perhaps others would care to give their advice as well). I have found that less than 0.70 g/L gives a fairly flat white wine after a couple years in the bottle. This can be a matter of taste, however, as I prefer crisp dry white wines, especially after a couple years of "vacation" in the bottle. I believe you said you were going to finish some of this slightly sweet. If this is the case, I strongly suggest a bit higher acid as you will need more to balance the residual sugar.
The hydrometer's PA reading prior to fermentation gives you an estimate of the alcohol if all of the sugars are consumed. So you will get approximately 12.7% alcohol when the final SG of the wine is down in the .992 - .995 range. If the fermentation stops and your final SG is higher, not all of the sugars were consumed (or there was a significant amount of other disolved solids in the must) and the alcohol content will be less than the original PA.
Thank for the info on PA, I was never sure weather or not the hydrometer took into account the final SG of the wine being below that of water.
I agree with your acid suggestions. Although the must is listed as having an initial TA of 5.2 g/l, it tasted a little more sour than that and I did not want to over do it. Is there anything wrong with waiting until bottling time to adjust the acid on the dry and off-dry portion separately?
Additions of acid are generally thought to be perceived as "better integrated" if made before fermentation. I shoot for 7-8g/L TA in my whites and I take measures to prevent malolactic fermentation. Selecting a starting acid level can be much easier to do with a dry white wine than with one that will be off-dry because you know ahead of time how much residual sugar will be in the final product ...nearly none! An off-dry style will undoubtedly require more acid than its dry counterpart to achieve good balance but the exact level of acid depends on the overall aromatics, extract and body of the wine with the sugar present. I would suggest starting your off-dry Gewurztraminer with 0.5 g/L higher acid than the dry. You can still "season to taste" prior to bottling but starting the acid a bit higher will keep your post-fermentation acid addition to a minimum. I shoot for a level that I perceive as just a bit too tart at bottling time, which is how I got to the 7-8 g/L range. This mellows over time and promotes very elegant aging.
I have to differ with you on the interpretation of potential alcohol. The majority of tables of PA / SG give the PA assuming the SG drops to 1.000. This is not dry. That is why negative numbers are given on hydrometers for PA when the hydrometer goes below 1.000. If you just go by the beginning SG you can have a 1-2.5 points error in your PA. The only table that I am aware of that assumes fermentation to true dryness is that of Duncan and Acton though I have been told that UC Davis also takes this into account.
Ray's assertion is correct. While simple conversions tend to work very well over time for established operations, Potential Alcohol calculation is by no means straightforward in the larger sense. The conversion factor of 0.55 to calculate Potential Alcohol from Brix is a pretty standard industry value and has worked well for me in general. Strictly speaking, every gram of sugar consumed by the yeast will liberate at most 0.511 grams of ethanol. This means that the 22.8 Brix could yeild a potential 11.65 w/w% Ethanol which is about 14.3 v/v%. To achieve this level of ethanol after fermentation would require absolutely complete extraction of all sugar, 100% yeast efficiency,
0% evaporative loss, and yeast fermentation to 0.00% residual sugar. Needless to say, this is highly unlikely so usefull "conversion factors" like the 0.55 discussed have become commonplace. I believe a range of conversion factors of 0.54 - 0.62 would cover the vast majority of observed results in the industry globally resulting in a v/v% ethanol range of
12.3% to 14.1% depending on the vast array of variables that can affect conversion, efficiency, and loss.
I agree with Aaron that you should bump up the acid a little higher.
I make Gewurztraminer and Riesling every year and like many I prefer them just off-dry. My procedure is to ferment them dry, usually around .992 SG and bottle them that way for the purpose of stability. I add a little sugar syrup to taste at the time of drinking. A Gewurz with your level of alcohol and a TA of 8 g/l would be nicely balanced especially if you drink it slightly sweetened as it will help bring out that unique and pleasant Gewurz flavour. I would personally avoid sorbate.
Thank you for your input. I am a little concerned with getting a Gewurz that is too "bright" since I tend to favor less acidic whites. The majority vote here is more acid though, so I am going to add 20 more grams tartaric to 7g/l and balance to taste at bottling time.
Every gram of sugar converted to ethanol will result in .511 grams of ethanol. More on this later.
This means that the 22.8 Brix could yeild a potential 11.65 w/w%
OK, I'll agree to this.
Don't forget the 5% of sugars that are used by the yeast but are not converted to ethanol. My references say about 1% goes to new cells and
4% will end up as other compounds like pyruvate, acetate, acetaldehyde, glycerol and lactate.
And because the hydrometer makers have to use one conversion factor. They can not take these other variable into account because they vary from fermentation to fermentation.
I can't agree with the .62. Theoretically possible but not practically possible. I think the .55 mark is more realistic in the home wine making world and I believe it can be lower than that.
But back to Ray's comment, what ever the hydrometer uses as a conversion rate (.55 is common because that is a common estimate and probably pretty accurate for most circumstances) this assumes that the wine has been fermented to dryness. That all of the sugars have been consumed and the SG is somewhere in the .992-.994 range.
If the SG is still at the 1.000 range, either there is still some sugar left or there was something other in solution besides sugar that effected the original SG. Either way, you did not get as much alcohol as anticipated, I would think around 1% ABV lower.
This is not to say that the hydrometer is a very accurate predictor of alcohol, only that it's prediction is based on all sugars being consumed and the final SG value being below 1.000.
The scale that is on both of the different hydrometers that I have matches very close to the tables given in such references as C.J.J. Berry in FIRST STEPS IN WINEMAKING and on Jack Keller's site. Both of these state that they assume fermentation goes to SG of 1.000 not dryness. This table can also be derived from the more basic table presented in Duncan and Acton's PROGRESSIVE WINEMAKING which is truly based on going to dryness by correcting back to an SG of 1.000. Consequently, the PA table on the hydrometers, at least the ones I have, are not based on fermenting to dryness. If you have a credible reference that indicates otherwise, I would like to see it. I really mean that as this is a topic of interest to me.
If you look at Jack's table on his hydrometer page, he shows the potential alcohol for a Brix "if the must is fermented to SG=1.000". This is not the same as what is shown on my hydrometers.
For instance, his table at brix 10 indicates a PA of 5.1%, my hydrometer shows a PA of approx. 5.5%. I think maybe Jack is giving you what the PA is if you go to 1.000, my hydrometer shows the PA if you go to dryness. I not sure if all hydrometers use this scale, but all of mine do.
Some of the following is using some general rules of thumb, but I think it show why there is a discrepancy.
A Brix 10 must, if fermented to dryness would probably finish at around SG=.997, subtracting from 1.000 would give us a .003 difference. Using the ROT of SG points divided by 4 = Brix, this would give us around a .75 Brix difference or IOW, the 1.000 must would have about .75% sugar remaining. Using a very standard .55 as a conversion factor of Brix to PA we come up with .41 PA, which explains the difference between Jacks PA (5.1) at a 1.000 end point and what is presented on my hydrometer(5.5) at dryness.
As we go up down Jack's table, this doesn't appear to correlate. If we only ferment to 1.000, as the original Brix goes up, we would be leaving more and more sugar in the wine, but Jack's table appears to be more of a simple .4 below my hydrometer's estimates.
My primary source of information is the course material for a UC Davis course in wine making. It doesn't really go in hydrometer readings but does talk about the conversion of sugar to alcohol and why a .55 conversion factor is a pretty good one if all sugars are consumed.
Of course this is only an academic exercise. There are way too many other variables to predict the real alcohol content. It is nothing more than a rough estimate no matter how you cut it.
BTW, could you check your hydrometers? Does brix 10 = PA 5.1 or 5.5 on yours? What about brix 20? Mine shows a PA around 11%. It's easier if you have the paper from a broken hydrometer because you can use a straight edge. If you don't, holding the hydrometer at the edge of the testing jar can help you judge across the scales.
DrinksForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.