So2 Additions Based On Must Volume?

[Tim F]

hey all, might be a stupid question but i've been wondering - if i have say 100l after crushing and calculate sulfite addition based on that but then get 70l of juice after pressing, won't I have more SO2 than I want in the finished wine? Or does some stay behind with the skins?

 

[vinlibervin]

Depends on what measurements you are working with - most initial additions of Kmeta that I have read work with the total volume of the must and not the volume of completed wine - whereas for eg additions of sugar you work with the volume of finished wine.

Most of the SO2 gets used up during fermentation and usually you do not add Kmeta again until the racking from secondary fermentation so the SO2 is there for a while.

 

[Greg.L]

I presume you are crushing then pressing straight away? If you are fermenting on the skins then you should calculate for the total fruit weight but if fermenting just the juice base your additions on the juice expected. If you are pressing crushed grapes with a basket press you will be lucky to get 70%.

The so2 is bound during fermentation but most stays as bound so2 in the wine. For a white wine you add more so2 as soon as fermentation is finished, to stop mlf and oxidation.

 

[Tim F]

That's right, this is for my white so I crushed and pressed pretty close together (left on the skins overnight). I made the mistake of basing the addition on the volume of fruit so I probably have 30% more SO2 in there than I needed. Given that, would I still need to do another addition after primary? This is assuming my yeast gets going at all of course, I'm using CY17 which doesn't like too much SO2.

 

[Greg.L]

Fermentation binds all the so2 so you always need to add more after primary (for a white).

 

[pokolbinguy]

I assume you have no way of measuring your SO2 ??? if you don't take along a few brews a winery close by or better yet to Adelaide Uni Waite campus and one of the students there would be happy enough to run a SO2 analysis for you for a brewski or 3. If you need a contact at the uni let me know.

What have you added and how much ?

Pok

 

[Tim F]

I had 100l of crushed fruit at pH 3.3 and added 14g of metabisulfate aiming for 60ppm - then pressed after 16 hours and got about 65l of juice.
Would definitely be interesting to check the so2 if you have a contact - what could I do if I figure out the level though?

 

[Tim F]

when it is time to transfer to secondary, could i get away without another sulfite addition if i flush the carboy and primary with co2 and pump the wine between vessels?

 

[Greg.L]

Tim, if you really don't like using so2 you can always risk going without. The concern is that your wine will take a lot of ageing so the risks are higher. Also the only way to reliably prevent MLF is to add so2 or keep it below 15C.

 

[Tim F]

I don't mind using so2, was just a bit concerned that i might have added a bit more than needed already at crush. How many ppm do you need to stop mlf? I didn't even realise you didn't want mlf in whites.

 

[Muggus]

I don't mind using so2, was just a bit concerned that i might have added a bit more than needed already at crush. How many ppm do you need to stop mlf? I didn't even realise you didn't want mlf in whites.

MLF is more of a concern in reds than whites, but inadequate SO2 certainly can cause a spontaneous MLF. It'd be handy to have a sterile filtration system at hand!
Failing that, if your primary is finished you're probably going to want to hit it with around 80ppm SO2...40 of which will be binded, leaving 40 free...of course this is dependant on pH, if it's higher than 3.5, i'd recommend knocking it down lower with some tartaric acid to begin with otherwise you might want to knock your SO2 addition to something like 100ppm.

 

[pokolbinguy]

Muggus is on to it.

Tim I'll put the feelers out for you and try and get someone to do a lab sample for you.

Pok