thick foam on the top

[nachov]

Hi everybody,

I'm making hard cider (with apple juice blend). 1.044 OG.

Can somebody tell me what is the thick yellowish-brown foam layer
which has formed on the top of my demijohn (sorry I didn't take a pic) ?

It happened a few hours after pitching my starter;
and it doesn't show too much activity in the airlock: it's bubbling like every 4 minutes.

I've heard that Krausen happens during active fermentation due to the proteins and yeast in suspension being pushed to the top of the fermenter by CO2 production.

In my case, it's most likely not a Krausen since it doesn't seem to be in active fermentation.
Actually, the active fermentation started this morning with airlock bubbling every 10sec
and the foam has sunk down.

I'm wondering if that foam layer is actually a yeast colony forming on the top.
I'm using Safale S-04 (which I believe is an ale yeast).
I know ale yeast are top-cropping yeast.

The airlock was bubbling every 4 minutes only.
Could it be that even a slight CO2 production could push some yeast in suspension and some proteins to the top of the fermenter?

I'm not worried, I'm just curious.


I'd welcome any comments.
Thanks.

 

[twistr25]

Sounds like it was a krausen to me. The bubbling says almost nothing about the fermentation, so go ahead and ignore that. It just means there is some gas escaping.

Some yeasts are top-cropper, but not all of them. S-04 happens to not be one of them, but it does have a fast fermentation. The krausen can linger for a while on top before falling through and that is perfectly normal. If you have any residuals on top, it is likely just yeast rafts and maybe some proteins. Sounds like everything is fine though.

Also in case you were wondering, let it be for at least 7-10 days after you pitch, then take a gravity reading, wait two days, then take another. If you're stable, go ahead and package.

 

[nachov]

Hi,

Thanks for you comment.

I forgot to mention that I took a reading a few hours after the foam showed up. It was SG 1.042 (so a loss of 2 SG degree).

Do you still think it was krausen from an active fermentation yet.
I thought Krausen stemmed from a massive CO2 amount escaping in a short time.

The SG reading seems to point out there was no huge release of CO2
which could have formed a Krausen.

I don't have too much experience with Krausen.
I've been making hard cider which lack of protein (compared to a protein-rich wort); so I haven't witness a gorgeous massive Krausen yet.

As I mentioned before, I'm not worried at all;
but I'm just wondering if a slight CO2 release could form a Krausen;
or it it's just the yeast crawling on the top of the fermenter.

Kind of like an invasion

 

[twistr25]

Still sounds like a krausen. Only other thing I can think of is an infection, so we'll stick with the krausen angle. Again, S-04 is not a top cropper, so it shouldn't be the yeast directly.

It sounds like it is working fine though, so just let it sit and do it's thing. I wouldn't worry about checking it again for a week at minimum.

 

[nachov]

OK. Sounds good. Very appreciated.

Just a last question to go further in my understanding of Krausen:

Does yeast oxidative respiration produce enough CO2 to form a Krausen?
In other words, does Krausen happen only in fermentation?
Or can it happen in oxidative respiration too?


Thanks.

 

[twistr25]

Correct, it only happens through the fermentation process.

From Palmer:
"A head of foamy krausen will form on top of the beer. The foam consists of yeast and wort proteins and is a light creamy color, with islands of green-brown gunk that collect and tend to adhere to the sides of the fermentor. The gunk is composed of extraneous wort protein, hop resins, and dead yeast. These compounds are very bitter and if stirred back into the wort, would result in harsh aftertastes. Fortunately these compounds are relatively insoluble and are typically removed by adhering to the sides of the fermentor as the krausen subsides. Harsh aftertastes are rarely, if ever, a problem."

 

[nachov]

Hi twistr25,


Just some heads up here:

Turned out you were right with option 2;
the tick foam was most likely an infection.

I ended up with a cider which smells sulphury.
I use yeast nutrients and vitamins addition in 3 stages during yeast growth to prevent that kind of smell during fermentation; but I did notice that sulphury smell at the start of the fermentation. I thought that was just a sluggish start.

With some yeast strain it's a normal smell at the start of the fermentation.
But in my case, I noticed that smell when the tick foam appeared.

Then that smell disappeared when the thick foam was reabsorbed into the brew; and the brew smelled awesome. Probably, the expulsion of CO2 during active fermentation dissipated the smell and the bacteria.

Then, my guess is that at the end of the fermentation,
the CO2 production dropped and the bacteria showed up again.

I don't have a Ph.D. in Microbiology; but I think I should have juiced the apples straight away after I got them from the store. I've heard Gliotoxin or Patulin bacteria's can grow in apples which have been taken from cold storage and kept at room temperature for a few days. Unfortunately, there is no visible signs of infection at naked eyes.

I guess it's a lesson to be learned: I should have been more careful. Besides, campden tablets addition after juicing was probably not enough to kill the bacteria.

Next time, I'll pasteurize my apple juice before fermentation.

Thank you for your contribution. I think you've pointed me in the right direction. I'll do better next time.

Cheers.

 

[twistr25]

No problem. If you can post a picture, I can't think of an infection that I've seen that hasn't manifested in some form on the surface. Might be worthwhile to let it ride for a bit and see if something good comes out of it.