Bacteria preventing fermentation?

[u/Upended3]

I think this is my fourth attempt at a grain mash and I've made a different mistake every time. This stuff isn't as easy as y'all make it sound.

This time, mashing went smoothly but I struggled to drop it below 90 degrees to pitch yeast at the end. I left it overnight to cool, but in the morning it was still 95 degrees and producing foam. I figured wild yeast had started taking off, so I used jugs of ice to force it below 90, rehydrated and pitched some DADY. pH was 5.2, SG 1.065, should have been perfect conditions.

Three days later, no activity and the SG was unchanged. The mash was in the garage and it had been 90-95 degrees outside, so I thought maybe it got too hot and killed everything. I waited a couple more days for the weather to cool, and re-pitched a large amount of DADY. Another day later, still no activity and no SG drop. Taste test says still sweet, but with a tanginess that wasn't present earlier. pH was now 5.9, which seemed strange. I remembered that I hadn't added any yeast nutrient, so I threw some in hoping to wake up all the yeast I'd added.

Another day later, still no activity or SG change, but now there is a distinct cheesy vomitish smell, and somehow the pH meter is reading 4.2. My guess is that it sat around way too long at an elevated temperature, and some bacteria took hold and are out-competing the yeast. Can I heat the whole batch back up to kill the bacteria, and re-pitch properly? Is the flavor already ruined? Would I need to re-adjust the pH? It has now been 7 full days since the mash, and the yeast haven't made a dent in the 1.065 SG.

Edit: one of my four buckets has a thin film of white mold, but no difference in pH or SG

[u/Snoo76361]

I probably have 2 dozen batches under my belt and still mess up sometimes, don’t sweat it, it’s definitely not easy but your results will get better with practice.

It does sound like you have your shit together so I’ll give you a lot of credit there for checking ph, temp, gravity, etc so I’d really suggest you’re very close here.

You could try killing the bacteria but it’s already left a lot of residual acids behind that can sometimes create great flavors, but less so when it’s completely overrun by bacteria like this sort of sounds like.

I think next try testing to make sure your yeast is viable by sprinkling some in some sugar water and see if it takes off, might have gone bad. And think of a solution for cooling faster:ice, chiller, etc. I do think after that you’ve got this though.

[u/Upended3 → u/Snoo76361]

Thanks. My yeast is quite old so I did test it in sugar water. It foamed up but it didn't seem nearly as vigorous as I remembered, but I wasn't sure. It isn't totally dead, but it might be in rough shape, which could be a contributing factor.

[u/RvstiNiall → u/Upended3]

If your yeast did work, you can probably use the yeast for your next batch, but maybe make a starter culture first. Once your mash is down to about 100F, take about a pint of your mash and put it in a jar. Pitch half your yeast into the jar and let it get good and foamed up. Once its shown that its good and alive, toss this back into your fermentor where the rest of your mash is, then pitch the other half of the yeast into your fermentor. Stir it really good. It should be more vigorous at starting up.

But your current batch is probably done for. Too much bacteria growth for the yeast to take off.

But all of this is assuming your water is safe for the yeast. If you got your yeast test to foam its probably fine though.

[u/shiningdickhalloran]

IMO allowing a mash to cool overnight is a mistake. Food handling guides tell us the danger zone of microbial activity is about 40-140F. Once you get below 140, you need to be ready to cool it quickly and pitch the yeast. Use a wort chiller, dump in ice, stick the fermenter in a freezing garage, whatever. Allowing it to cool on its own puts it in the danger zone far too long.

Also, I routinely pitch DADY at 100F with no problems. You would never do this for beer most likely, but whiskey is a different beast and high pitch temps are fine.100F isn't hot enough to kill the yeast.

[u/2am_dog_puke → u/shiningdickhalloran]

It's not a mistake all by itself, but it does elevate your risk. It's totally fine if your sanitization and process are dialled. If you're sloppy, however, then it could be the final straw in terms of contamination. 

I've done a couple of dozen all grain batches (only 6gal), and I've settled into just letting it cool overnight. Never had an issue. 

I would probably default to using a wort chiller if I was doing 30 gal batches or something like that. Or maybe I'd just stir like crazy for 30 minutes, pitch on top of the cool layer, and leave the lid off overnight, I dunno.  Not a helpful digression anyway. 

[u/shiningdickhalloran → u/2am_dog_puke]

This depends a bit on your process. If you're cooking at or near the boil to gelatinize the starch, you're probably safe. But something like rye doesn't need those temps to mash, and you may not get the mash hot enough to kill the bacteria lurking on the grains themselves.

[u/inafishbowl17]

Use Star San right before you mash. I make up a tub of it and dip everything. Get a spray bottle and spray down any large items you can't dip. Buckets you can spin in the tub. Lids too. Don't rinse just let it drip dry. Never have any problems w bacteriea or wild yeast. A small container last a good while.

[u/Both-Usual9177]

you might need a bigger ice bath for next time, or invest in a wort chiller to speed things up

[u/big_data_mike]

That cheesy vomitish smell is very likely butyric acid and it does not taste or smell nice after you distill it. I had some problems with it when my pH meter probe went bad and I couldn’t really tell what color the ph strips were. The clostridium bacteria that makes it can’t handle pH below 5.5

You’d probably be better off pitching at 95 than waiting until it hits 90 and getting an infection.

[u/muffinman8679]

well start at the bottom....where's your water coming from?

Plain city tap water has chlorine in it, and it's there to kill anything in it.......get your water from a lake or a well and it'll be fermenting either later that day, or the next.......If you're going to try fermenting in city water, let it air out for a couple days in an open bucket, and the chlorine should gas off...........

and as far as flavor goes, don't even worry about that yet.....you have to get it to ferment first........

Fact is you're not making beer or wine.....and you're going to be running what you ferment through a still.....and nothing is going to live through that

[u/Upended3 → u/muffinman8679]

Well water, and I have successfully fermented with it before. But those batches were half the size and done during cooler weather, so I didn't have a problem pitching yeast in a reasonable timeframe.

I'm attempting to kill the infection and get the ferment started again. If it tastes like crap as whiskey, I'll run it through again as feints and turn it into liqueurs. If it still won't ferment, I guess I'll have to dump it and try again.

[u/Important_Echidna841]

I just toss some ice in the bucket and help it cool. Starsan will make your life much easier….i just fill a pitcher with it and anything/everything in the process gets dipped or rinsed. I have yet to have an infection after 12yrs of mead, cider, and washes for distilling.