I think I am having some regrets over last nights brew session. I had an overnight mash that sat a little too long. Despite wrapping it really well the temp had dipped down into the 100F range and the resident bacteria on the grain started to party. The surface certainly had that awful vomit like aroma. Butyric acid like aroma (is that pedio at work?) I don't do to many overnight mashes, but sometimes they are useful. I normally get to them within 10 hours, but this one was closer to 20+ hours. Even my normal great wrapping of the cooler, couldn't hold it up enough. To give you an idea of the other temp complications, I prepared some starsan to do some racking of another beer. The foam was freezing instantly. The beer I was racking actually started to ice over on the surface as I racked! So I decided to bag the night. Chalk the whole thing up to a little experiment in sour mashing. Sadly, I threw out the mash.... Weighing the value of my time, the temps in the garage, the cost of the yeast and hops. I figured maybe it was best to cut my losses. What would you have done? Saved it. Let it sour more. Fermented it and see what happened? I did taste some wort from the bottom. It was certainly tart and had the start of some nice lactic character, no real acetic note. But hard to tell with the massive sweetness in the wort too.
I'd have soured it at that point. And hopbursted it with nelson, citra, or amarillo a la red swingline or batch 60.
I would have given another day or two, try to keep the temp around 100 still and then boiled it. Tasted it, tossed some hops in for a short boil, chilled and tasted it. If it sucked, then less than an ounce of hops and some fuel for the boil went into it.
I don't blame you for throwing in the towel. Yeah, it might have been fine, but at that point, there was little time or money invested. Treat it as a lesson learned, no harm done.
If you've got butyric acid in the mash, that's clostridium butyricum and you don't want to use a mash with that going on. (If the mash stayed up over say 120 for the whole time, you probably'd be fine since they can't work their "magic" that high. Using the mash would have probably resulted in vomity beer unless you drove off the acid during the boil.
If you don't want a sour beer, didn't plan to make a sour beer, and don't want to dedicate extended time to continuing with the process of making a sour beer, then definitely dump it. Also, per above, not every spontaneous infection is going to produce a good sour beer anyway. Even if you pressed on, you still might have ended up having to dump it, so look forward and not back. As much as I love a good sour beer, I still rely on starting it off in a planned way (pitching the bugs I want, keeping the cold side clean/sanitized). If I was tasting what you were describing at any point in my sour fermentations, I would probably consult with a couple of people who have been through the process before and be prepared for bad news. I have never had a maturing sour taste as foul as you describe, and would guess that things had gone wrong.
What is the likely hood that some of the nasty acids could have or would have been driven off in the boil? I wasn't sure if that would have been likely.
Some probably would - but not enough for me to feel comfortable that you'd be below sensory threshold. To give you an idea butyric acid has a threshold of about 0.3 ppm
I recall ann interview with chad jakobsen about butyric acid being a desireable compound when working with brett as the brett will break it down into tropical flavor esters. I've taken a lot of shit out of context though, so thiis may be the case.
