1. Home
  2. Winemaking Craft Forum
  3. S02 levels commercial vs. amateur

S02 levels commercial vs. amateur

i've got a batch of okanagan merlot that began the ferment @ pH 3.35 with TTA 6.0 (yes, i corrected a bit). with MLF complete, and S02 added, the wine has been in my cellar (9-10 degree C) for over a month. at present, the pH has got rather high (3.79), the TTA is indicating 5.8, and my free S02 is 35ppm. i'm not a terrible chemist, and i have some faith in my numbers, derived by vacuum aspiration. so, i pose two questions with respect to this endeavour:

  1. to get the optimal (minimal) amount of mol. S02, it appears i need around 50ppm free. i have both the australian chemistry and winemaking guides, and they speak of only 15-20ppm required for red wine storage, although a caveat mentions that you'll need to go a bit higher for pH's above 3.5. I realise that my pH of essentially 3.8 would require something past the 'slightly' higher value of 20ppm. Is my current
35ppm safe for my 400+ litres of Merlot?

  1. i tested a 2002 Quail's Gate Merlot, which had a pH of 3.65. I was shocked to find the free S02 measured less than (probably much less) than 16ppm. a same vintage wolf blass shiraz, pH 3.5, weighed in at

14.5ppm free S02. Why are these numbers so low? Is it just that the wine will be consumed quickly and not cellared for a long time, or is there something else at hand?

Many thanks for any opinions or answers. Darin

Reply to
Darin Young
Loading thread data ...

I'd say you're OK at 35 ppm, but I wouldn't go lower.

The free SO2 probably was higher when the wine went into bottle, but the dissolved oxygen reacted with it and now it measures lower. The same thing happened with my 2002 Chardonnay. It went into bottle at ~55ppm free, and 6 months later it measured ~35ppm.

FWIW, 0.8ppm molecular free SO2 is the usual target for white wines, but many winemakers target for reds is more like 0.6ppm molecular.

Tom S

Reply to
Tom S

">> 1. to get the optimal (minimal) amount of mol. S02, it appears i need

I calculate that you need 57 ppm to get to .6 molecular with a pH of 3.8 - I think I'd add more SO2 assuming you'll be aging this wine for some time.

Ed

Reply to
Ed Marks

What's the structure of the wine like? Does it seem like a wine you'll lay down for a decade+ or something you'll drink within the next few years? If you'll be going through it pretty soon (~5 years or so) I'd leave it alone at 35 ppm.

Tom S

Reply to
Tom S

">> I calculate that you need 57 ppm to get to .6 molecular with a pH of

3.8 -

Tom,

What's your experience doing this? I have some wines aging now that have higher pH than I usually get (probably in the same 3.8 range). I typically try to keep my SO2 levels as low as possilble, but at a molecular level that will keep the wine stable - so I shoot for .6M. Have you found that lower levels are OK for up to 5 years? The 35 ppm that Darin has would be about .37M - it seems that you think that's enough. Thanks for sharing your experience with doing this.

Ed

Reply to
Ed Marks

I have _white_ wines that have held up for 5 years with relatively low SO2.

35 ppm should be safe enough for a red wine - but again, a lot depends on the structure of the wine. Some wines just aren't destined to improve much over time, no matter what the SO2 is.

Tom S

Reply to
Tom S

Tom & Ed, thanks for you informative comments. I ran this batch through a mild extended maceration. So, i think it's going to take a few bottle years for the tannins to mellow. It is extremely interesting to see how commercial practises differ from what the typical amateur will do, following guidance from literature rather than experience.

Anyhow, so long as my wine is ok at 35ppm free until i bottle, i'm happy. As that event is still nearly two years away (after stainless steel and barrel aging), i'm not sure what the pre-bottling structure will turn out to be like. If the tannins have adequately polymerized, we'll have this one on the table before five years. If not, i suspect more S02 and longer bottle time will follow.

Reply to
Darin Young

You didn't mention that you were planning to give the wine extended aging prior to bottling. That changes things a lot!

During barrel aging, the wine is exposed to a very slow oxidation through the barrel staves. The free SO2 declines during this time and must be periodically replenished. You should measure it every 3 or 4 months and make adjustments as necessary to keep it at whatever your target SO2 is.

Also, before you ask, it's _not_ recommended that you add a sufficient excess of SO2 at the beginning to take the wine all the way through barrel aging.

You should do weekly or bi-weekly barrel tasting and topping to check on the wine's progress, inspecting the surface to be sure that there's no film floating on it and sniffing at the bunghole to be sure the area remains clear of off odors. I find that dipping the end of a silicone bung into meta (the powder itself) just before jamming it back into the barrel after topping helps prevent such problems.

Tom S

Reply to
Tom S

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.