(un)importance of SO2 in home winemaking

[jesseb]

Soon I will start making my first batch of red wine made from grapes (must actually). I've did some research, online and reading the book Modern Home Winemaking, by Daniel Pambianchi. One thing that is not really clear is how/if to use sulfites, in particular how to measure free sulfites. I know why sulfites are used in wine and I can understand the importance of them on a commercial scale, but does the average joe home winemaker use them? I don’t think every home wine maker has a semi-lab and working with strong acids/alkaline solutions to do an aeration test?

The book more or less states it is really important to dose the correct amount of sulfite and you can only do so by measuring how much to add. On the other hand, some online sources just seem to free ball it, a tablespoon of potassium metabisulfite here and there. Too much sulfite isn’t really good for your health right? Or am I overcomplicating things and isn’t it that important all together? There are a lot of wines made without the use of sulfites, are those stable enough to age them for a couple of years?

So to summarise: is sulfite used in home wine making, and if so, how to dose it? If not, is the wine stable enough to store it for a while?

 

[Brooothru]

I make mostly kit wines (have for over 25 years) and they all include a sachet of either K-Meta or Na-Meta. Yes, I always use them. But 1T is waaaay too much SO4. The amount of sulfate for a 6 gallon/30 bottle kit is approximately 1/4 teaspoon.

 

[Bobby_M]

I would say that it's possible to protect the wine from oxygen with careful process and equipment, but not in the way home wine makers usually proceed. What I mean, is that if you rack the wine a few times to clear it up and then siphon into bottles, all of those moves add up to a LOT of oxygen exposure. Sulfite additions are the only way to prevent that oxygen exposure from doing noticeable and lasting damage. On the other hand, if one were to pre-purge vessels and use inert gas pressure to push the wine from vessel to vessel (including the final bottles), it could keep a wine bottle stable without sulfites. I don't know a single home winemaker that does the latter. Don't get me wrong, I know plenty of people that sulfite and open-air racks the wine. I know quite a few that don't use sulfites and also rack the wine carelessly but claim it's great (it's not).

 

[Brooothru]

I would say that it's possible to protect the wine from oxygen with careful process and equipment, but not in the way home wine makers usually proceed. What I mean, is that if you rack the wine a few times to clear it up and then siphon into bottles, all of those moves add up to a LOT of oxygen exposure. Sulfite additions are the only way to prevent that oxygen exposure from doing noticeable and lasting damage. On the other hand, if one were to pre-purge vessels and use inert gas pressure to push the wine from vessel to vessel (including the final bottles), it could keep a wine bottle stable without sulfites. I don't know a single home winemaker that does the latter. Don't get me wrong, I know plenty of people that sulfite and open-air racks the wine. I know quite a few that don't use sulfites and also rack the wine carelessly but claim it's great (it's not).

Hey, Bobby.

In my winemaking I ferment in a sealed stainless steel Ss Brewtech brew bucket. The initial introduction of the must into the fermenter and dilution with water makes it virtually impossible to begin with a totally O2 environment. When fermentation begins, usually within 6~8 hours, the O2 gets rapidly depleted.

When primary fermentation is complete, I transfer under vacuum into a carboy pre-rinsed with an NaMeta spray. This limits O2 exposure as the (now) wine is stabilized and clarified in the carboy.

The method I use for vacuum transfer is with an Enolmatic bottler that sucks the air out of the carboy while simultaneously drawing the wine out of the fermenter. I'll add that the fermenter is pressurized with ~1psi CO2 to prevent implosion from the vacuum draw from the carboy.

Once transfer is complete, a slight amount of O2 ingress is unavoidable when the vacuum gets broken before an airlock can be installed, by the NaMeta stabilizer will mitigate the damage.

When I bottle the wine after bulk aging, I once again use the vacuum Enolmatic to suck the air out of bottles that have been rinsed with a weak NaMeta spray. The bottles are then immediately corked. They age exceedingly well. Just tonight we enjoyed a Stag's Leap Merlot that had been vinted in 2013, and it was excellent with no sign of oxidation.

 

[Coffee49]

O2 is your best friend and your worst enemy. Look at S02 as the sanitation helper, any tool or container should be soaked in it prior to starting the wine process. Transfer obviously poses the greatest risk of contamination, I keep the rackings down to two, 1/4 tsp. of So2 at first racking and bottling, and do very little degassing. Time is a winemakers best friend

 

[Brooothru]

O2 is your best friend and your worst enemy. Look at S02 as the sanitation helper, any tool or container should be soaked in it prior to starting the wine process. Transfer obviously poses the greatest risk of contamination, I keep the rackings down to two, 1/4 tsp. of So2 at first racking and bottling, and do very little degassing. Time is a winemakers best friend

Absolutely!

I also do a single racking after fermentation, which is generally 90% (or more) complete after 2-3 weeks. Give it another week or two for the gross lees to settle, and I do a transfer under vacuum into bulk aging. Transferring with a partial vacuum helps to degas the wine.

SO4 is a necessary evil to keep O2 at bay, but it is a case of less being more. I never add more than 1/4 tsp per 6 gallons, but I also "mist" all transfer equipment and containers with an aqueous solution of NaMeta using a spray bottle.

 

[jesseb]

Thanks for the replies. So if I understand correctly, you (people who replied) actually do not measures/calculate the amount needed to end up within the required sulfite range? What about over/under dosing?

 

[Coffee49]

Correct, the 1/4 tsp. Measurement is for a 5-6 gallon carboy, no final range is calculated, my experience is that a 1/4 tsp. added to the carboy of wine with the intention of sitting for 3-4 months prevents slow O2 intervention. Timing of every other racking so to do a final adding of bisullfite at bottling is the desire.

 

[Bobby_M]

Hey, Bobby.

In my winemaking I ferment in a sealed stainless steel Ss Brewtech brew bucket. The initial introduction of the must into the fermenter and dilution with water makes it virtually impossible to begin with a totally O2 environment. When fermentation begins, usually within 6~8 hours, the O2 gets rapidly depleted.

When primary fermentation is complete, I transfer under vacuum into a carboy pre-rinsed with an NaMeta spray. This limits O2 exposure as the (now) wine is stabilized and clarified in the carboy.

The method I use for vacuum transfer is with an Enolmatic bottler that sucks the air out of the carboy while simultaneously drawing the wine out of the fermenter. I'll add that the fermenter is pressurized with ~1psi CO2 to prevent implosion from the vacuum draw from the carboy.

Once transfer is complete, a slight amount of O2 ingress is unavoidable when the vacuum gets broken before an airlock can be installed, by the NaMeta stabilizer will mitigate the damage.

When I bottle the wine after bulk aging, I once again use the vacuum Enolmatic to suck the air out of bottles that have been rinsed with a weak NaMeta spray. The bottles are then immediately corked. They age exceedingly well. Just tonight we enjoyed a Stag's Leap Merlot that had been vinted in 2013, and it was excellent with no sign of oxidation.

It just goes to show how variable everyone's process is. You're using a combination of oxygen avoidance and abatement.

 

[Brooothru]

It just goes to show how variable everyone's process is. You're using a combination of oxygen avoidance and abatement.

Exactly. I recognize that it's virtually impossible to eliminate O2 exposure, but mitigation after fermentation is the best way to keep oxidation at bay and allow the wine to properly age.

 

[Raptor99]

I weigh powdered Kmeta on a small scale, so I calculate the amount needed based on pH. This article explains how to do that: Guide to SO2 Management and SO2 Calculator | MoreWine The chart referenced in the article no longer appears, but you can see the chart here: https://www.accuvin.com/wp-content/uploads/2015/04/How-SO2-and-pH-are-Linked.pdf

I combined this on a spreadsheet. I keep this chart handy in my wine making area:

	Desired Free SO2	Kmeta
pH	ppm=mg/L	g/gallon
2.9​	11​	0.073​
3.0​	13​	0.086​
3.1​	16​	0.106​
3.2​	21​	0.139​
3.3​	26​	0.173​
3.4​	32​	0.213​
3.5​	40​	0.266​
3.6​	50​	0.332​
3.7​	63​	0.418​
3.8​	79​	0.525​
3.9​	99​	0.657​
4.0​	125​	0.830​

 

[jesseb]

I weigh powdered Kmeta on a small scale, so I calculate the amount needed based on pH. This article explains how to do that: Guide to SO2 Management and SO2 Calculator | MoreWine The chart referenced in the article no longer appears, but you can see the chart here: https://www.accuvin.com/wp-content/uploads/2015/04/How-SO2-and-pH-are-Linked.pdf

I combined this on a spreadsheet. I keep this chart handy in my wine making area:

	Desired Free SO2	Kmeta
pH	ppm=mg/L	g/gallon
2.9​	11​	0.073​
3.0​	13​	0.086​
3.1​	16​	0.106​
3.2​	21​	0.139​
3.3​	26​	0.173​
3.4​	32​	0.213​
3.5​	40​	0.266​
3.6​	50​	0.332​
3.7​	63​	0.418​
3.8​	79​	0.525​
3.9​	99​	0.657​
4.0​	125​	0.830​

Thanks, this is handy. I've found the MoreWine article before, but didn't saw the section about not having a SO2 test kit.