Gose - Wort Souring WTF moments!

Okay, full history is here: http://www.brewcommune.com/forum/viewtopic.php?f=5&t=2600

Long story short...

Last Thursday, I made a lacto starter with one vial WLP677. Keeping it above 100 degrees, it had activity.

Last Friday, I mashed my Gose, sparged and collected the wort, and chilled to ~115 degrees. Note: I did not pasteurize.

Prior to adding the lacto, I used the refractometer to get my preboil gravity. 1.035, right on the nose for Beersmith.

I then pitched the lacto, let it run until first thing Sunday morning at a temp of ~90 degrees, noting that I actually had activity going on in the wort all day Saturday. A lot of agitation, and almost a "hissing / fizzing" sound coming off it.

Sunday morning, I take another preboil gravity reading using my hydrometer. 1.004! I checked with refractometer, and based on OG and refract reading, Beersmith corrects it to 1.004 as well.

The beer tasted okay. Maybe a light tartness, but overall not overwhelmingly sour nor any other crazy flavors from other bugs that I could tell.

Upon attempt to boil, the boil started at 200 degrees rather than 212.

I completed my boil, and thinking that I probably just boiled off all my alcohol, added ~3# of sugar and 0.5# DME to the boil.

I took refractometer readings through the boil and saw the number going up, and after the boil, the refract reading conforms to an OG for these beer of 1.029. And I'll assume that my boil got rid of any alcohol that was there.

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So what happened? Did something get in there and ferment this whole thing out? Was it the lacto? Can it get it all done that quickly?

And if it fermented out, how much damage did I do by boiling it out and adding new fermentables?

I'm not an expert but*

My gut says your 004 hydro reading seems questionable. Even if you contaminated your lacto culture with yeast (that was weird to type) that's a lot of chomping to accomplish in a few hours overnight.

Let's assume your post-sour reading is bunk and back calculate from your post-boil. Your sugar and DME is ~.046 per gal per# so that puts you at 1.032... so it looks like my assumption was wrong, Your post Sour reading appears correct!

What got in there? Who knows, too bad you killed it... If it was clean tasting that was some bad@ss yeast. What did you end up fermenting your post boil with?

The post-boil was S-05. Nothing exciting

Almost the exact same experience with my recent Berliner Weisse. I went from 1.032 to 1.010 in 48 hrs. I did not boil afterwards though and pitched Brett Brux in what was left of the wort. I used Wyeast 5335 and a second lacto starter cultured from raw grain though. Mine also tasted fairly clean but is decently sour.

I still have yet to get any solid answers on how/if lacto can do this alone, as well of if it produced any alcohol in the process...

I brewed a Berliner Weisse with nothing but WL Lacto. It fermented quickly/actively/completely, but yielded only minimal tartness. Very strange. Lacto can be as attenuative as Brett, depending on the strain.