fermenting Kahm Yeast early on in a long term ferment. What should I do?

[Chilli Willi]

I've got a batch of fermented hot sauce on the go which is about two weeks old. It's started forming Kahm yeast, which is a really bummer as the plan was to ferment this batch for four to six months. I've removed the Kahm yeast with a ChemSan'ed spoon once already, but it grew back within a couple of days. So today, I did a brine flush by filling up the fermenting jar with fresh brine until what ever Kahm yeast particles I could see, were flushed out of the jar. I then left less headroom in the jar, wiped the inner surface with ChemSan, and sprayed the outer jar with it too, just to be safe. I've also put stronger brine into the airlock, not that I think it'll make much of a difference.

My question is, (1.) where do I proceed from here? I really wanted to ferment this batch for longer but I don't want the Kahm yeast to ruin the batch. (2.) Should I just carry on cleaning out the Kahm yeast and ferment for as long as I want or should I reduce the amount of time I ferment the batch for?* (3.) The batch in question is in close proximity to other batches of hot sauce. They're all airlocked and are currently showing no signs of yeast growth but (4.) should I move the yeasty batch away somewhere else to prevent cross-contamination?


*I tested the pH of the brine and it's already at 3.8, so I guess it's technically ready to bottle... I just want more funky flavour though!

 

[Downriver]

@Chilli Willi Yeah, kahm yeast can be troublesome. What to do, watch to do?

My short answer: skim all the yeast off and process this ferment.

Longer answer: Same as the short answer, but here's my opinion why. When you opened the jar, you released all the co2 that had been created during active fermentation, and replaced it with oxygen. By the way, even though you scraped out all the kahm, it will come back. That's a fight you won't win. Worse, now that active fermentation is done, there will be little to no new co2 produced to displace the oxygen just introduced into the jar. Now, there's an excellent chance actual mold will move in. Then, you'll have to throw the whole batch out.

Now, are there other things you can try? Sure. You could try vacuum-sealing, to remove the oxygen. That might work, but that's a totally different way to ferment. Or, you could add more fresh veggies, and perhaps a little sugar, and try to restart primary fermentation. That could cause the whole co2/oxygen displacement cycle to begin again. That might work. The problem with both of these options is, if they don't work, you'll probably end up throwing the whole batch out. That would be a shame. Sooo, again, I recommend you process this batch and save it from the compost pile.

Just my 2c. YMMV

And remember the #1 rule in fermenting: DON'T OPEN IT! (until you're ready to process it)

 

[Bou]

+1 for what Downriver said

@Chilli Willi Kahm yeast is there and now whatever you do you are stuck with it! The more you'll try to get rid of it, the greater the chances that you're gonna end with mold too IMO. Besides, Kahm yeast is not as bad as most think as long as it is kept under control (so it doesn't turn into mold).

For example, this ferment is now more than 2 months old and as you can see the Kahm yeast is everywhere! It appeared and grew quite rapidly but went into iddle mode after maybe two weeks. I'm still monitoring it but I don't plan to process this batch for another month, maybe even later. Note: There is an airlock filled with Star San on the lid and I also use cabbage leaves to keep the vegetables from floating to the surface and growing mold.

Here's some reading on the subject :

(The Art of Fermentation by Sandor Ellix Katz)

And from a beer making perspective:

(Escarpment Laboratories)

 

[Chilli Willi]

Starting this reply now might be a mistake, as I'm really short on time. So please forgive me it it's not particularly complete. I do plan to make a more thorough reply in a few days, once I have more time. As I'd like to share my experience in the hopes that others might learn from my mistakes (I'd also like to complain about Kilner brand fermentation lids!).

I've been doing a lot of thinking about my next move and seen as though I could really do with not having to bottle the sauce until the weekend at the earliest, and seen as though Kahm Yeast isn't the problem that I'd built it up to be, I've decided to take a wait and see approach until I have the time to bottle. Or more precisely, if I can't see any mold tomorrow, then I'm leaving it until the weekend, as I'll be out of town for a couple of days. It's a decision that was in part informed by your reply @Bou, merci beaucoup.

I've also given plenty of thought to what you said, @Downriver. Thank you for your input. To be honest, if it wasn't for the time constraints, I would be inclined toward following your advice but I figured that as the chillies I'm fermenting were sort of free.... if ever I'm gonna wait and see how things progress at the risk of wasting a batch, perhaps this is a good time?

As I said, there's a lot more I would like to say but it'll have to wait a few days but in the mean time. I would appreciate any input in regards to the decision of whether to heat treat the sauce when it comes time for bottling. I left my first batches live and kicking, and they're tasting better and better. Which is why that's what I had planned to do with all of my current batches. Given the issue with Kahm yeast though, does that mean I should heat treat the batch in question?

​

 

[Bou]

For what it's worth, I always bring my ferment to a short boil to kill Lactobacillus & friends. This ensures that I don't end up with an "explosion" , from a full bottle (I already had to deal with beer bombs, what a mess!) or a splash of sauce directly in the face (or even worse, in the eyes!) when you open the bottle. You probably don't need to boil because most yeasts and molds are denatured at around 170F if I remember well.

On a side note, I would try to bring my pH lower; 3.8 is supposed to be fine, but if your reading device is not properly calibrated, the pH may actually be a little higher than you think...

(https://www.ars.usda.gov/ARSUserFiles/60701000/FoodSafetyPublications/p328.pdf)

 

[Downriver]

...does that mean I should heat treat the batch in question?

@Bou and I belong to the same choir. I'm singin' the same song. I heat-treat ALL sauces, regardless of kahm yeast presence.

 

[Chilli Willi]

For what it's worth, I always bring my ferment to a short boil to kill Lactobacillus & friends. This ensures that I don't end up with an "explosion" , from a full bottle (I already had to deal with beer bombs, what a mess!) or a splash of sauce directly in the face (or even worse, in the eyes!) when you open the bottle. You probably don't need to boil because most yeasts and molds are denatured at around 170F if I remember well.

Thankfully, it looks like I may have some time for further thought on the question of processing.

It's been three days since I did the brine flush and whilst the Kahm yeast has regrown, I can't see any signs of mold. So I'm still leaning towards just leaving it for a while yet. Not least because the fermentation still looks like it's active enough to create CO2. Plus it'll give me time to do some more research, and everything is part of the learning process. So even if what's in the jar might turn into a loss, I will still have gain something from it.

On the subject of bottle explosions. I have been conducting my own, wholly insufficient but interesting non the less experiment on the subject. With my first batch, as I wanted to taste how the sauce developed over time, I didn't pasteurize it. I just put it in sterile bottles and jars, and refrigerated it. Since it went in the fridge, I've been giving the bottles a precautionary burp and watching and listening to what the sauce does when I crack the seal. I've been leaving it longer and longer between burps and so far, I've seen no signs of gas escaping, or significant, noticeable, continued fermentation. The flavour keeps getting better though. I know that in no ways proves that I won't get a fizzy, ceiling redecorating bottle at some point but until these words come back to bite me, I think keeping the sauce live at the risk of that happening, is a risk I'm willing to take.

On a side note, I would try to bring my pH lower; 3.8 is supposed to be fine, but if your reading device is not properly calibrated, the pH may actually be a little higher than you think...

If my previous batch is anything to go by, the pH should be lowered to around 3.5 once I add the vinegar. Maybe even slightly lower as I plan to use Lemon juice too, with this batch. With the first batch of sauces, I added Lime juice to one of them, which lowered the pH .2 lower than the non-Lime juice sauces.

As for my pH meter... it's an Apera PH60, which was calibrated less than a month ago. So I'm not overly concerned about it being way off but I wouldn't mind re-calibrating it again just to be sure but in order to retest the brine, I'd have to open the fermentation vessel again. Which is something I really don't want to do.

Just going back to the question of heat treatment... I'm tempted to have my cake (or hot sauce as the case may be), and eat it too. I might heat treat half the batch, and leave the rest live. And then see if one set of bottles develops Kahm yeast, whilst the other doesn't. It'd also be really interesting to find out how the flavour development of treated vs. untreated sauces vary.