# Total SO2 and sensory limit



## Rob_S (Jan 11, 2017)

Hi folks,

Wondering what you find would be the total SO2 added to red wine before you end up detecting it in the final product which leads to a chemical taste?

I've read 100 ppm, 120 ppm, and 150 ppm. I now have a wine in a barrel that is loosing about 20 ppm of free SO2 every 4 weeks. Since the pH is about 3.63I need to keep the free SO2 at 54 ppm for 0.8 molecular. I've added so far 50 ppm at the crush, after the MLF the free SO2 was down to 20 ppm so added 34ppm, now added another 24 ppm as it had dropped to 30 ppm in the barrel after one month. So I think I should only leave it in the barrel for another month, and might have to add another 20 ppm at that point and that would bring my total additions of SO2 to 128 ppm. Thinking that might be the limit or surpassing it a bit before detecting too much SO2?

Rob


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## NorCal (Jan 11, 2017)

I've added twice that without issue.


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## jburtner (Jan 11, 2017)

Here's an interesting SO2 doc that may or may not help -
http://srjcstaff.santarosa.edu/~jhenderson/Sulfur Dioxide.pdf

It says legal commercial limit for total SO2 is 300 PPM and SO2>100 PPM can affect taste... Lots of info in that doc.

I would guess that it varies depending on the wine and environment too and 100-200 may be near threshold depending on those details.

Where does that put us in general if bulk ageing for a year and adding 1/4 tsp every three months so 1.0tsp over the period of a year?

Cheers!
-jb


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## NorCal (Jan 11, 2017)

1/4 tsp = 50ppm in 5 gallons. 

For me: once after crush, once after mlf racking, then every 6 weeks until bottling. I check with my Vinmetrica and do 200-300ppm total adds without any perceived impact.

Note: we have a higher pH fruit than most and even with preferment adjustment, the pH still tends to be high.


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## Rob_S (Jan 11, 2017)

jburtner said:


> Here's an interesting SO2 doc that may or may not help -
> http://srjcstaff.santarosa.edu/~jhenderson/Sulfur Dioxide.pdf
> 
> It says legal commercial limit for total SO2 is 300 PPM and SO2>100 PPM can affect taste... Lots of info in that doc.
> ...



Maybe I'll take it out of the barrel soon and accept that as it's limit as time spending under oak. In a wine with a lower pH that will be another matter and could spend more time under oak.

Sounds like one tsp into say 5 gallons over a year would be adding 250 ppm if I've done the calculation correctly and would think that would be past the sensory threshold. 

In your article you quote it says if you aim for molecular above 0.7 you end up with burnt match taste. I thought a molecular higher than that say at 0.8 was ok and quite common, from what I've read elsewhere and in this calculation table it can be set to 0.8. I've aimed for 0.8 in several batches and kept the to total SO2 below 100 at wines with lower pH like 3.5 and wine turned out fine without burnt match taste.

https://winemakermag.com/1301-sulfite-calculator

Thanks everyone for your input.

Rob


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## Johnd (Jan 11, 2017)

Rob_S said:


> Maybe I'll take it out of the barrel soon and accept that as it's limit as time spending under oak. In a wine with a lower pH that will be another matter and could spend more time under oak.
> 
> Sounds like one tsp into say 5 gallons over a year would be adding 250 ppm if I've done the calculation correctly and would think that would be past the sensory threshold.
> 
> ...



If you barrel age for years, and many do, you'll put in way more than those limits, but much of it becomes bound so2, and free so2 is what I believe the limits address. I barrel age for six months, and during the course of that time, add 50 ppm monthly, well over 300, but most of it is bound. Several more months in a carboy, more SO2, but still undetectable, at least to me.


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## grant675 (Jan 26, 2017)

Johnd said:


> If you barrel age for years, and many do, you'll put in way more than those limits, but much of it becomes bound so2, and free so2 is what I believe the limits address. I barrel age for six months, and during the course of that time, add 50 ppm monthly, well over 300, but most of it is bound. Several more months in a carboy, more SO2, but still undetectable, at least to me.



My understanding is different, that the legal limit applies to TOTAL SO2, since bound/neutral SO2 will essentially unbind when ingested. Though I just read that somewhere on the internet. There's also the small amount of naturally occurring SO2 to consider, which could even be around 10-20 PPM?? What haven't wrapped my head around yet is why keep adding sulfites to a wine aging in oak barrels? Don't you want the slow oxygenation that the barrel offers, and won't persistently maintaining free sulfite level contradict that process? A similar example, general reading tells me that when aging in a glass & airlocked carboy, many rack about every three months and add sulfites to maintain the free level (or some just add the same sulfite amount each racking). Why bother to rack and sulfite in the first place if the wine is already cleared and not dropping sediment? Why not just leave it alone if no additional oxygen/contaminants are getting though the airlock? If racking to oxygenate, wont keeping up with the free sulfite level contradict the oxygenation like the barrel example? I always thought you'd sulfite shortly before a major activity, like a planned racking off major sediment or bottling, but I don't see why so much racking and sulfiting is necessary. As has been pointed out, you can exceed the legal limit fairly quickly.


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## grant675 (Jan 27, 2017)

jburtner said:


> Here's an interesting SO2 doc that may or may not help -
> http://srjcstaff.santarosa.edu/~jhenderson/Sulfur Dioxide.pdf
> -jb



Pg 11 is very helpful. I had seen that before, but the beginning was so painful I never actually made it to pg 11.


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## Johnd (Jan 27, 2017)

grant675 said:


> My understanding is different, that the legal limit applies to TOTAL SO2, since bound/neutral SO2 will essentially unbind when ingested. Though I just read that somewhere on the internet. There's also the small amount of naturally occurring SO2 to consider, which could even be around 10-20 PPM?? What haven't wrapped my head around yet is why keep adding sulfites to a wine aging in oak barrels? Don't you want the slow oxygenation that the barrel offers, and won't persistently maintaining free sulfite level contradict that process? A similar example, general reading tells me that when aging in a glass & airlocked carboy, many rack about every three months and add sulfites to maintain the free level (or some just add the same sulfite amount each racking). Why bother to rack and sulfite in the first place if the wine is already cleared and not dropping sediment? Why not just leave it alone if no additional oxygen/contaminants are getting though the airlock? If racking to oxygenate, wont keeping up with the free sulfite level contradict the oxygenation like the barrel example? I always thought you'd sulfite shortly before a major activity, like a planned racking off major sediment or bottling, but I don't see why so much racking and sulfiting is necessary. As has been pointed out, you can exceed the legal limit fairly quickly.



Wow, that's a lot!! I'm not a chemist or attorney, but I'll take a shot. 

Firstly, legal limits are of no concern to me as a home winemaker, but taste obviously is. 

In practice, my so2 additions, whether in barrel or carboy, are determined by testing the so2 levels and making appropriate adjustments to maintain free so2 at the proper level, based upon pH and wine color. My wines in carboys, under airlock, rarely need as much as 1/4 tsp every few months, although that is the rule of thumb practiced by most who don't measure so2. I don't rack in the absence of significant sediment, but do maintain so2 levels to keep the wine free from infection. Airlocks and bungs are not a perfectly airtight seal and do allow some exchange. 

As far as barrels, they are checked and adjusted monthly, my small barrels can go from proper levels to near zero in under a month. Micro oxygenation is good, oxidation is bad, although slow, controlled oxidation over long time periods are part of what improves wine with age, the way a corked bottle ages. Again, not a chemist, but so2 doesn't seem to stifle the effects of microx in a barrel, but it does control spoilage organisms. 

Short story, measure and adjust as needed to protect your wine based on its pH and color while aging, and one last time at bottling.........


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## NorCal (Jan 27, 2017)

SO2 acts as an antioxidant as well as a microbial deterrent. If your barrels are topped, I think the greater benefit is fighting organisms which could otherwise spoil the wine.


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## havlikn (Jan 27, 2017)

I understand the fact that so2 drops over time. My question is if you keep adding and adding so2 every month to maintain the proper level, does it have adverse effects on the wine. Meaning if I add 5 grams a month for 24 months and this keeps my level at 45 ppm, is there any adverse effects


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## TonyR (Jan 27, 2017)

There are some people that can taste SO2 in wine. My palette isn't that refined but have had people ask what is that chemical taste.


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## grant675 (Jan 27, 2017)

I suppose a good question is how do commercial wineries bulk age their wines in barrels or carboys for years, while keeping under the legal SO2 limit, or even the sensory limit, which could be as low as maybe 1/3 the legal limit (100PPM)? There's no way they can be opening up the barrels or carboys every 1 - 3 months and adding sulfites each time. I get that SO2 also helps prevent bacteria infestation, but if you're not opening the barrel or carboy, is there really much risk there? I think the bigger risk to oxidizing and infestation is when the winemaker keeps opening up the aging vessel! Why not just let it be and bring the sulfite level back up prior to the next transfer or bottling? I did read one interesting article that stated some wineries blow inert gas through the equipment (tubes, pumps, etc), and to fill headspace with the gas before closing up the vessel. Maybe that would really help to minimize alcohol to acetaldehyde transformation, which is stealing your free SO2. Maybe then you can open the vessel more often for tasting if the oxygen is removed prior to closing it back up. This is really nothing new I suppose, and there's no hard set rules. I just struggle with the idea that persistent sulfiting is a good replacement for process. It sort of becomes a crutch, but eventually the total SO2 level will be doing more harm than good.


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## grant675 (Jan 27, 2017)

TonyR said:


> There are some people that can taste SO2 in wine. My palette isn't that refined but have had people ask what is that chemical taste.


 

I taste it, but have no idea at what PPM level. I think just about every fruit wine I've bought from a local commercial winery has over sulfited to the point that its noticeable. These are typically sweet winces since the sugar will bring back the base fruit flavor and help sell it as a fruit wine. Once SO2 is noticeable it's difficult to get past it when drinking, and I've dumped bottles before. That's exactly what I aim to prevent in my own fruit wines. I'm not one to beat the organic wine drum, but I think over sulfiting (total SO2) will ruin what was an otherwise great wine.


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## NorCal (Jan 28, 2017)

Taste, test, top is a standard winery cellar maintenance process. It would be nice to set it and forget it, come back a year later and have nicely aged wine, but that isn't the practice in any of the commercial wineries that I know.


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## baron4406 (Jan 31, 2017)

Could you sterile filter your wine to get rid of the sulfates? Asking because there was a blurb on Facebook a while back about this funnel you'd pour your wine thru and it would remove sulfates(and thus no headache the day after). My wife really won't drink commercial wines anymore, they all give me a massive headache the next day


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## cmason1957 (Jan 31, 2017)

Does your wife have reactions to raisins, dried apricots, other dried fruits? All of this have significantly more sulfites than wine. Generally sulfite reactions are respiratory, not headaches.


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## baron4406 (Feb 1, 2017)

Not really cmason, then again she doesn't eat alot of dried fruits


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## Sudz (Feb 2, 2017)

There is a new product out there called "the Wand". It's a odd looking spoon which is used to eliminate sulfites in a glass of wine.

Have any of you tried one of these? 

If so, can you describe the effect?


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## crushday (Nov 30, 2019)

Johnd said:


> I barrel age for six months, and during the course of that time, add 50 ppm monthly


John, how are you applying sulfite during barrel aging? I've been adding a full teaspoon at barrel fill (6 gallon) and thinking that would be fine for six months. Sounds like that's a failed thought.


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## Johnd (Nov 30, 2019)

crushday said:


> John, how are you applying sulfite during barrel aging? I've been adding a full teaspoon at barrel fill (6 gallon) and thinking that would be fine for six months. Sounds like that's a failed thought.



Best bet is to measure and adjust and top up monthly to maintain proper levels, that is how I handle wines in barrels. What I have found, generally speaking, is that my 6 gallon barrels needed 1/8 tsp per month to maintain levels. The 30 and 60 are in the same vicinity, half of the 1/4 tsp per 6 gallons applied monthly.


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## ZebraB (Dec 2, 2019)

One thing that I learned from my first kit is that I added the packet in the kit and then 1/4 tsp at 3 month mark. When I finally purchased and SO2 tester, the SO2 level was 35 at 6 months which was too high for a white wine with a low PH. 
So my advise is to calculate the initial potassium metabisulfite level needed for the wine because it is apparent that the kit makers want to insure success for a quick aging timeline.

https://www.rjscraftwinemaking.com/craft-and-cork/sulphites-and-wine/

"there will still be some present in the final product (10ppm), as it is a natural by-product of fermentation If you are adding sulphites via the add pack, as per our instruction sheets then the final product will have between 35-50ppm"


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