Sulfite levels during undisturbed aging

[RylanJacobs]

When making sulfite additions, I aim for 50 PPM and assume 0 PPM baseline when doing the calculation. Conventional WMT wisdom suggests adding 50PPM (1/4 tsp) every 3 months. Winemaker Mag suggests adding 15ppm every month. I am challenging whether or not the 0 PPM baseline assumption is correct when bulk aging.


How much do sulfite levels decline when bulk aging at a steady temp in a carboy under airlock? Assuming no headspace and no removal of the airlock, would the sulfite levels decline? If I add 50 PPM after not touching the wine for 3 months, is it likely that I am over-sulfiting?


Final question: At what point (PPM) is sulfite generally detectable in wine? I had routinely been adding 50PPM every 3 months without any obvious detection. So my anecdotal evidence suggests detectable levels are probably >100PPM. Winemaker Mag suggests so2 levels could be detectable around the 50PPM, depending on pH.

The easiest solution would be to spend $2,000 on a Sentia wine analyzer. I guess xmas is right around the corner....The Vinmetrica kits do seem like good options, but I am curious to know everyone's thoughts here at WMT!

 

[winemaker81]

The baseline assumption of 0 ppm SO2 each time works. I haven't found research on the topic to suggest a scientific rationale, so I assume that the figure arrived from decades of practical experience by winemakers. 1/4 tsp per 19-23 liters was the figure when I started winemaking 4 decades ago, and I've seen nothing that indicates it's wrong or should be changed. Since it works, I don't bother with relatively expensive SO2 testing, as I see it as a pointless expenditure.

I have adopted the model of adding 1/3 the K-meta dosage each month when I open barrels to top them, because the barrels have to be opened and there is air exposure. I have no intention of doing the same for carboys, as there is no reason to open them. Every 3 months is sufficient.

As to the 3 month rule, SO2 gets used up as it neutralizes things, including oxidation caused by sunlight. Replenishing it is a time-proven rule.

Regarding detection? I've known a few people who could detect SO2 at an estimated 150-180 ppm. I couldn't detect it nor could most people. I've never met anyone who could detect SO2 below that -- it's very likely some folks can, but they don't drink my wine so I don't worry about it.

 

[RylanJacobs]

Thanks, Bryan! Insightful as always.

 

[Rice_Guy]

The vinmetrica will give a reading of 2ppm, ie one drop of the titrant will push the reading over 50. (miliamps) ,,, this is a redox issue. ie watch oxygen exposure.

I have not seen aging tests vs SO2 readings. There is a basic problem in sampling for testing. If one has a gallon with 5cm of headspace and samples, simply opening the carboy adds about 2mg oxygen per liter. Of course fives and six gallons have a lower ratio of added oxygen.

I expect a reading with the Vinmetrica on a red or a tannic apple wine. I assume 0ppm with low tannin wines and have run whites that take one drop of titrant. My view is opening and adding fresh air is a risk especially in small carboys, avoid unnecessary opening.

 

[bjoll001]

I use the Vinmetrica SO2 meter. It is easy to use and works well. I check every few months SO2 levels and notice from one wine to another the SO2 levels drop differently. I adjust based on the SO2 readings. The levels drop differently in different types of aging vessels also. For my barreled wine, the SO2 levels drop much more than wine in carboy during the same time period ( which makes sense since barrels do mico ox and lose wine to the Angels). I have to sulfite the barrels more often than carboys due to that.
In the end it is probably fine to add 50 ppm every 3 months to protect the wine but I recommend knowing the SO2 before bottling to make sure in right range for bottle aging as once it is in the bottle no more can be added.

 

[mainshipfred]

It's my understanding a percentage of the SO2 gets using up immediately. I also use 0 as a base line and my initial dosage is 60+ ppm. On occasion I test the levels prior to adding the sulfite and find that in a properly topped up carboy the levels drop very slowly. I've had wines aging for 6 months or more without adding and still levels in the 20s and 30s. Barrels of course are a different story.

 

[RylanJacobs]

I use the Vinmetrica SO2 meter. It is easy to use and works well. I check every few months SO2 levels and notice from one wine to another the SO2 levels drop differently. I adjust based on the SO2 readings. The levels drop differently in different types of aging vessels also. For my barreled wine, the SO2 levels drop much more than wine in carboy during the same time period ( which makes sense since barrels do mico ox and lose wine to the Angels). I have to sulfite the barrels more often than carboys due to that.
In the end it is probably fine to add 50 ppm every 3 months to protect the wine but I recommend knowing the SO2 before bottling to make sure in right range for bottle aging as once it is in the bottle no more can be added.

Thanks for the reply. What is your preferred SO2 level for bottle aging?

 

[bjoll001]

Thanks for the reply. What is your preferred SO2 level for bottle aging?

I sulfite different for every wine based on the pH. Some wines have as low as 20 ppm and others up to 60 ppm depending on pH. The lower the pH, the less SO2 I use. I generally follow the recommendations on wine maker magazine online sulfite calculator which will give you the ppm to add for your pH and tell you how much in grams to add for the volume of wine you are treating. I usually add 10 extra ppm of sulfite than the recommendation for bottling to take into account sulfite lost during the process of bottling.

 

[mainshipfred]

I also sulfite based on the pH and do use extra but I use closer to 25%. Attached is the chart.

 

[Christopher Anderson]

The baseline assumption of 0 ppm SO2 each time works. I haven't found research on the topic to suggest a scientific rationale, so I assume that the figure arrived from decades of practical experience by winemakers. 1/4 tsp per 19-23 liters was the figure when I started winemaking 4 decades ago, and I've seen nothing that indicates it's wrong or should be changed. Since it works, I don't bother with relatively expensive SO2 testing, as I see it as a pointless expenditure.

I have adopted the model of adding 1/3 the K-meta dosage each month when I open barrels to top them, because the barrels have to be opened and there is air exposure. I have no intention of doing the same for carboys, as there is no reason to open them. Every 3 months is sufficient.

As to the 3 month rule, SO2 gets used up as it neutralizes things, including oxidation caused by sunlight. Replenishing it is a time-proven rule.

Regarding detection? I've known a few people who could detect SO2 at an estimated 150-180 ppm. I couldn't detect it nor could most people. I've never met anyone who could detect SO2 below that -- it's very likely some folks can, but they don't drink my wine so I don't worry about it.

My question is how do you add K-meta to the barrels or carboys? Just dump the powder in and stir slightly or vigorously? or mix with wine or water? then do you stir the barrels or carboys?

 

[winemaker81]

My question is how do you add K-meta to the barrels or carboys? Just dump the powder in and stir slightly or vigorously? or mix with wine or water? then do you stir the barrels or carboys?

The first 6 months I add K-meta, stir the barrel with a drill-mounted stirring rod, then top up. The last 6 months I add K-meta and then top up, to avoid stirring up the lees.

 

[Christopher Anderson]

The first 6 months I add K-meta, stir the barrel with a drill-mounted stirring rod, then top up. The last 6 months I add K-meta and then top up, to avoid stirring up the lees.

You have the 20+ years of expertise (meaning you made a lot of mistakes!). I am attempting to "catch up" and mostly avoid the "oops" that can and will occur or to lessen them. I am assuming you top off with a similar wine from your vast collection....

 

[winemaker81]

You have the 20+ years of expertise (meaning you made a lot of mistakes!). I am attempting to "catch up" and mostly avoid the "oops" that can and will occur or to lessen them. I am assuming you top off with a similar wine from your vast collection....

Wise choice. I much prefer to live vicariously through the mistakes of others, whenever possible. It's a lot less painful than doing it myself!

My advice to others is a mixture of personal experience, research, and paying attention to what others on the forum have done. SO2 testing is case in point -- I've been using 1/4 tsp K-meta per 19-23 liters and it's always been satisfactory + folks on this forum have conducted testing + at least one research paper indicated that SO2 levels are what I expect = don't bother with testing. This doesn't mean that testing has no value -- it means *I* don't see any value.

OTOH, there is plenty of unambiguous practical chemistry behind the "do not use bleach in your winery" rule so I simply accept it as the wise choice.

The most difficult thing about advanced winemaking is that there are contradictory choices that are all valid. This is why I recommend asking "why?" someone follows a course of action, as knowing the answer to that question helps me decide what I want to do.

 

[NorCal]

The US legal limit on total (not free) SO2 is 350 ppm, which would be quite a bit. The sensory limit is very much dependent upon the individual.

pH has a non-linear impact on the efficacy of SO2, thus you have to add a lot more on the higher pH wine. Example: adding a 1/4 table spoon every three months to a 3.3 pH Sauv Blanc in a carboy would be an unnecessary overkill. However, it would be insufficient for a Sierra Foothill Cab Franc with a 4.0 pH, especially if the fruit wasn't great.

I did an experiment years ago and looked at the same wine, made at the same time that I stored in a 60 gallon barrel, 30 gallon flex tank and a 5 gallon glass carboy. When I needed to add 40ppm to the barrel, I needed to add 20ppm to the flextank and only 10 to the glass carboy. My point is that the container also has a large impact on the amount of SO2 required, with the glass carboy providing the most protection.

 

[Christopher Anderson]

Wise choice. I much prefer to live vicariously through the mistakes of others, whenever possible. It's a lot less painful than doing it myself!

My advice to others is a mixture of personal experience, research, and paying attention to what others on the forum have done. SO2 testing is case in point -- I've been using 1/4 tsp K-meta per 19-23 liters and it's always been satisfactory + folks on this forum have conducted testing + at least one research paper indicated that SO2 levels are what I expect = don't bother with testing. This doesn't mean that testing has no value -- it means *I* don't see any value.

OTOH, there is plenty of unambiguous practical chemistry behind the "do not use bleach in your winery" rule so I simply accept it as the wise choice.

The most difficult thing about advanced winemaking is that there are contradictory choices that are all valid. This is why I recommend asking "why?" someone follows a course of action, as knowing the answer to that question helps me decide what I want to do.

That no bleach rule is mandatory. I can remember using bleach to clean out my dogs' outside drinking bowl. Even after a full day and a real cleaning, they did not drink out of it. It took 2 days for the stink to dissipate. If I use any now, i can smell it on my hands for days. I now use hydrogen peroxide and it is an "organic" cleaner. also use it in my pond to kill the algae and the fish don't mind the H202. It gets rid of the organic matter in many items. I might use it, after an oxygen cleaner to rinse the carboy and bottles before using sanitizer because of its use as an oxidizer, bleaching agent, and antiseptic.

 

[NCWC]

It's my understanding a percentage of the SO2 gets using up immediately. I also use 0 as a base line and my initial dosage is 60+ ppm. On occasion I test the levels prior to adding the sulfite and find that in a properly topped up carboy the levels drop very slowly. I've had wines aging for 6 months or more without adding and still levels in the 20s and 30s. Barrels of course are a different story.

We just filled 8 barrels from SS tanks about a week ago. ML was complete, I added 50 ppm SO2. I just checked them today they were at 25 ppm give or take. I like to maintain 40 ppm during aging. I age for 2 years at least. I test and top 1st of the month.

 

[RylanJacobs]

We just filled 8 barrels from SS tanks about a week ago. ML was complete, I added 50 ppm SO2. I just checked them today they were at 25 ppm give or take. I like to maintain 40 ppm during aging. I age for 2 years at least. I test and top 1st of the month.

Fascinating! This is the type of data I am curious about. Did you do a rack when you added the 50 ppm?

 

[rsportsman]

A relevant article by Daniel Pambianchi: SO2_Management