Contamination in Kettle sour??

[merline]

Hi,
I've done a few kettle sours (typical BIAB mash, quick boil, cool to 95*, add lactic acid to adjust pH, then 1-2 days with a few Swanson probiotic pills, etc). But due to out-of-town scheduling, with my most recent kettle sour I needed to leave the kettle at room temp for 4 days. When I went to proceed, there were some small slightly blue-ish star shaped colonies - maybe 2-3mm in total size.

Unfortunately I didn't photograph them (I know... stupid move) but instead just spooned them out of the kettle. I check the SG post souring and usually it's the same as pre-souring. But this time is was 10pts lower. From 1.07 to 1.06. Am I correct in assuming the contamination was from a yeast like Brett? And not mold or other bacteria. I am under the impression that mold or other bacteria wouldn't eat the sugar like that. Oh and it smelled pretty good; a bit of a mint aroma.

thanks!
-Ellis

 

[RPh_Guy]

Am I correct in assuming the contamination was from a yeast like Brett?

Yes, that gravity drop indicates some kind of yeast, probably not Brett (it's too slow).

The floating colonies weren't necessarily the same organism that caused the gravity drop.
I'd be most worried if it were mold, which can produce toxins.

 

[cactusgarrett]

If it's not a pervasive infection, and since it smelled okay, I would guess a full boil (30-60 min) would salvage this - if you haven't already gone this route.

 

[merline]

Thanks. I did continue with full boil, etc. It's fermenting now (Belle Saison) and does smell nice. I was worried about the mold possibility but I couldn't find any pictures of mold matching what I saw (still mad at myself for not taking a photo of it!).