Mold growing on must

Hello all. I'm a long-time brewer and am now advising my father-in-law on making Perry, since he grows oodles of astringent, old-english pears that are perfect for this brew. He decided to try fermenting wild, and has had the must in his carboy for about 3 weeks at rather cold temperatures (40-50's F) as suggested in the book he has been following. There is a nice line of mold growing along the top of the must, and although the top does look a bit cheesy, there has been no visible activity in the airlock. Yesterday we tried measuring some properties, and find the sugar content has dropped 1 Brix (16 to 15) in 3 weeks, at a surprisingly low pH of 3.3. Honestly I have no idea what things should look like when doing a wild fermentation but the presence of the mold at this low pH surprised me, and worries me into thinking we should do something about it.

I suggested that maybe we pitch a little commercial starter like Montrachet yeast in, just to give the natural beasts a little help, and that maybe keeping the carboy at "outside temperatures" as recommended in his British manual could be too cold for this process.

I also mused that we might want to rack the must out, hit with campden tabs to kill everything, then restart fermentation with commercial yeast.

The perry doesn't taste bad or smell bad, but I'm really not comfortable with a mold-infected brew. Thoughts on how we should proceed?

Happy thanksbrewing everyone!

-ben

sideshow_ben said:

I also mused that we might want to rack the must out, hit with campden tabs to kill everything, then restart fermentation with commercial yeast.

-ben

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Yep, that's what I'd do. It sounds infected, not fermenting. I'd use the campden tablets, wait 24 hours and then pitch a good quality commercial yeast.