Good advice. Thank you. I will probably not touch it and I know I won’t be bottling until August 2023. Just to be clear, when you say increase SO2, my typical dose is 1/4 tsp per 5-6 gallons. If I use a rounded 1/4 tsp would that be enough?
The waiting is important. I set up a tartaric addition taste test with my aforementioned pinot noir and all of the acid additions - even the modest ones - stood out as intrusive when tasted the same day as the addition.
I like to measure SO2 and dose accordingly by weight, so I had to look it up. That 1/4 tsp works out to 45ppm in 5 gal, which is probably about right for pH 3.8. So I'd maybe keep the same dose but maybe dose a little more often than every 3 months? Maybe someone else can weigh in?
Based on that chart you posted, the 80ppm target is for 0.8ppm molecular SO2, which is appropriate for whites; however I think the typical target for reds is 0.5ppm molecular SO2 (for example see here). So the 1/4tsp per 5 gal sounds about right to me. I targeted 45ppm while my (pH3.8) wine was aging, then bumped it up to 50ppm for bottling.
Do you know the TA? Has it gone through ML? How much SO2 have you added thus far, and at what stages? Adjusting acid post-ferment is risky, but certainly an option. I would forego any acid adjustments if it tastes balanced, I'd be more concerned with needing to add a higher dose of SO2 to reach an optimal working level of FSO2. Do you have the option of blending in a higher acid finished wine?
Looking at your chart. The SO2 column is mg/L. We usually talk about additions in ppm. I'm not sure if mg/L is the same, is it? Also, how does the chart tell you to use 80 ppm for a 3.8 ph?
They are the same thing.
Let me take this one step further. If a wine needs 50 ppm to be protected is that at every racking (3 months)? Rack three to four times a year and that becomes 150-200 ppm. Correct?
There was a time early on in my winemaking when I didn’t understand the importance of SO2 and I would rack with no chemicals at all for a year. The wine turned out fine. Dumb luck?
You need more than 50ppm for a 3.78pH wine if you want at least 25ppm FSO2 to protect the wine. Blindly adding 50ppm at each racking is ill advised; you could end up with 250 TSO2 and still have 0 FS02.
Wine can be quite resilient if left on healthy lees, in a sterile atmosphere. I've made syrah with zero SO2, whole cluster ferment, finished pH 4.01 and the wine was stable and stunning.
I would not. Look at it from this POV -- why would you change the flavor arbitrarily to change the amount of preservative added?
Maybe bench test to try a smaller quantity acid addition... may be a win-win... more stable wine and better tasting. Naturally, if the flavor goes on the wrong side of where you want to be, I wouldn't make the adjustment on the whole batch. I, personally (and I know this wine isn't meant for me) prefer a pH of 3.65 max. Without trying some things, you'll never know what you're missing.
There is a calculator at SO2 Addition as Potassium metabisulfite (K2S2O5) that will do the math for you. Enter volume and target ppm (both in your units of choice) and it'll tell you how much KMBS (K-meta) you need.
