Early sulfite prevent MLF if cider contaminated later?

[Scott Harring]

I had a few of my wild ferments undergo MLF last year prior to fermentation.  I wasn't too happy with the change in flavor profile.  I'm now adding 30 ppm sulfite to the must the day of pressing.  This prevented MLF in my later batches last year.  

Question is: Does an early sulfite addition prevent MLF later if the cider later comes into contact with a small amount of non sulfited juice? Wondering how worried I have to be about adding a small amount of non sulfited juice to top off a carboy months from now.  Or if I forget to sterilize my racking cane and it's contaminated with MLF bacteria etc.  Thanks.

[Patrick McCauley]

Hey Scott. With such a small sulfite dose, I would definitely expect MLF to occur later on in the process, even without the addition of a small amount of unsulfured juice. Others on this forum would have a stronger understanding of the science behind that, but I get some MLF in my minimally sulfited ciders all of the time. Never had it happen that early in the process, but I always do a small sulfite dose immediately after pressing.

Pat

On Mon, Sep 14, 2026, 7:25 PM Scott Harring <harrin...@gmail.com> wrote:

I had a few of my wild ferments undergo MLF last year prior to fermentation.  I wasn't too happy with the change in flavor profile.  I'm now adding 30 ppm sulfite to the must the day of pressing.  This prevented MLF in my later batches last year.  

Question is: Does an early sulfite addition prevent MLF later if the cider later comes into contact with a small amount of non sulfited juice? Wondering how worried I have to be about adding a small amount of non sulfited juice to top off a carboy months from now.  Or if I forget to sterilize my racking cane and it's contaminated with MLF bacteria etc.  Thanks.

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[Scott Harring]

Thanks Pat, that makes sense.  I'll keep an eye on it this Winter.  Post fermentation MLF might be welcome with some of the ciders I'm working on this year, but not everything.   My early MLF experiences previously were pretty negative and halved TA right out of the gate.  Appreciate your help.  

Scott

[Taylog1]

I had the same when I used to use 50ppm at outset but left on the gross lees for too long - I think it binds with the solid material. Had to reacidify with malic acid. Now I don't use any at outset (I get very vigorous fermentations), take it off the gross lees say after 4 weeks ish, and add 100 ppm then. Seems to be working better at the moment, but I'm low in pectin so the solids drop out pretty quick.