Chronic off-Flavour in BIAB

“The tastes gets more mild with bottle conditioning after about 3-4 weeks,…”

That detail has got me thinking that there are excess levels of acetaldehyde in your beers. The favor descriptor often used for excess acetaldehyde is green apple favor but cidery would applicable as well.

During primary fermentation acetaldehyde levels of 20-40 mg/L are created but by the end of primary fermentation they decrease to 8-10 mg/L.

Assuming that it is high(er) levels of acetaldehyde that is causing the cidery flavor I would suggest that you leave your beer in the primary for a longer period of time to permit the yeast to ‘clean up’ the excess acetaldehyde that was generated during the primary fermentation.

Cheers!

 

I agree with almost all of this. I just wonder why acetaldehyde levels would still be unusually high if the OP is already going two or three weeks out in primary? 3 weeks should already be more than enough time. If 'green beer' is to blame, I think a secondary fermentor w/ limited headspace would be more beneficial. Because...

Another possibility is oxidation. Ethanol can undergo chemical or metabolic oxidation to yield acetaldehyde and/or acetic acid - but this wouldn't happen rapidly under 'normal' circumstances unless some sort of oxidizing agent is present. First thing that comes to mind is OxiClean residue, but there's no mention of that from the OP - only StarSan.

It's all-grain, too, so the old 'stale LME' scapegoat is also N/A.

hmmm

 

I agree with that. I was wondering to myself if he is experiencing a 'weak' primary fermentation for some reason. I would guess that "US-04 9g rehydrated" should provide an adequate yeast cell count. I was a bit surprised of 9 grams since my sachets of Fermentis dry yeast are 11.5 grams.

You are experienced with S-04, do you think that 9 grams rehydrated is enough for a beer of OG = 1.057?

Cheers!

P.S. Maybe the rehydration process was 'off'?

 

I wouldn't even rehydrate it, lol. OP is only making 8L of beer (2.1 gallons). 9 grams is plenty. That said? I'd also just use the whole 11.5 g pack - because I probably wouldn't bother to save the remaining 2.5 g.

 

I had this problem with a batch last year - it tasted like apples, but not like green apples. It was a really slow ferment, so I gave it about 5 weeks in the primary, but other than that I couldn't figure out what the problem was. In retrospect, I wonder if I didn't oxygenate the wort enough before pitching? Oh well, I brought the keg to a party and that took care of that problem for me.

 

Whoops, I missed that part.

Yeah 9 grams should be sufficient here. I have no idea why the acetaldehyde would not be 'cleaned up' in three weeks.

Hmm?

Cheers!

 

"Aerate by shaking for about 2-3 minutes"

I would guess that the wort was sufficiently aerated there. Plus, Lallemand (Danstar) states that their dry yeasts do not require aeration since the dry yeast process:

"No, there is no need to aerate the wort but it does not harm the yeast either. During its aerobic production, dry yeast accumulates sufficient amounts of unsaturated fatty acids and sterols to produce enough biomass in the first stage of fermentation. The only reason to aerate the wort when using wet yeast is to provide the yeast with oxygen so that it can produce sterols and unsaturated fatty acids which are important parts of the cell membrane and therefore essential for biomass production."

Cheers!

 

If the beers were fine before but not know, my first guess would be your water changed. Are you using campden tablets or otherwise mitigating chlorine? It can lead to a medicinal/sharp sort of flavor.

ETA: BEFORE mashing it

 

You are using twice as much yeast as recommended. This can be more detrimental than beneficial. Extreme over pitching can create more acetaldehyde than a proper pitch. It also has the ability to absorb more acetaldehyde, IF the yeast doesn't drop too fast. Yeast can drop out very quickly in such a small batch.

I'll assume you have used similar pitch rates in the same sized batches without this problem. If that is the case, you could very well have yourself a Zymomonas infection.

Tap water can contain bacteria even if it's chlorinated. Remove chlorine and chloramine with a Campden tablet, then boil it to sanitize.

 

But if the OP DOESN'T rehydrate, half the cells die and the pitch is just right! Yay cell death!

Therefore, definitively, rehydration ruined this beer! x)

[/Brew_Betty]

 

That's right! I'd rather not have 80 billion dead cells pooping in my beer, so I'd rehydrate half a pack here.

 

I'd add two bottles of ECY and a big stir bar, put it on my stir plate and call it a starter - but this thread isn't about me.

 

May not have an effect on your beer but I had a bad batch I narrowed down to adding unboiled tap water to my fermenter. Boiling sanitizes and helps reduce chlorine in the water you're adding so if I ever top off my fermenter I use boiled and then cooled water that I've also carbon filtered.

 

6B/g is the minimum, but the actual count can be as high as 20B/g. Conventional wisdom and several calculators pick a cell count in between the two. Usually around 15b/g.

The Mr Malty calculator suggests 5 grams of rehydrated yeast for your batch. One 9g or 11.5g pack is plenty for a 20L medium gravity batch without having any negative consequences that an under pitch could produce.

I'm not saying you pitched too much yeast. However, over pitching can cause the problems you are experiencing. Since you have ruled this out as a possibility, your beer is clearly infected with Zymomonas.