Trying To Determine Off Flavours.

[Truman42]

I have a steam beer that's been bottled since 18 December.
Ive noticed a very distinct sour sort of taste and after doing some research concluded it may be the green apple taste caused by acetaldehyde. I can't really be sure as my ability to smell and taste off flavours isn't very good.
I just know it has a noticeable sour or vinegar type of taste.

Now from what I've read of acetaldehyde and it's cause, it can be due to incomplete fermentation or longer lagering time required.

I brewed this batch for a week and had stable fg for 3 days before CCing. (I had reached the required FG also)

(It's interesting to note that my first extract brewed in winter and sat below 14c for two weeks had the same taste which I thought was "kit twang")

So if acetaldehyde is caused by incomplete fermentation won't this possibly create bottle bombs once the wort warms up in the bottle??

And if longer lagering time is required I would have thought that 5 weeks + would be ample time?

Finally if someone has a good nose for this sort of thing and would be willing to taste a sample I would like to send you a sample to try.

Cheers

 

[Dazza88]

If the sour gets worse over time it might be infection. I think green apple may dissipate.

 

[tonyt]

I have a steam beer that's been bottled since 18 December.
Ive noticed a very distinct sour sort of taste and after doing some research concluded it may be the green apple taste caused by acetaldehyde. I can't really be sure as my ability to smell and taste off flavours isn't very good.
I just know it has a noticeable sour or vinegar type of taste.

Now from what I've read of acetaldehyde and it's cause, it can be due to incomplete fermentation or longer lagering time required.

I brewed this batch for a week and had stable fg for 3 days before CCing. (I had reached the required FG also)

(It's interesting to note that my first extract brewed in winter and sat below 14c for two weeks had the same taste which I thought was "kit twang")

So if acetaldehyde is caused by incomplete fermentation won't this possibly create bottle bombs once the wort warms up in the bottle??

And if longer lagering time is required I would have thought that 5 weeks + would be ample time?

Finally if someone has a good nose for this sort of thing and would be willing to taste a sample I would like to send you a sample to try.

Cheers

Hi Truman.

I had that green apple taste with my first ever home brew......I beleive it was due to too high.... and too greater fluctuating ferment temps. since i got temp control haven't had a prob.

Cheers

 

[Steve@PMF82]

Get a more experienced brewer to taste it.

Clubs, good home brew store ect ect.

 

[Nick JD]

I just know it has a noticeable sour or vinegar type of taste.

I wouldn't describe acetaldehyde as vinegar. However, it does describe ethanoic acid very well.

 

[Truman42]

@tonyt...I do use a temp controller for my brews and with this one. Just didn't have it with my extract back in winter. So that rules that out.

@nick JD... I cant really tell if it's green apple or vinegar. But the missus is leaning towards sour green apple taste. That's why I want an experienced brewer to try it for me.

 

[Greg.L]

It is very good experience for a homebrewer to have experience of samples of the various off-flavours like acetaldehyde, diacetyl etc. I know for wine there are kits that you can take a sniff of the various samples, this is really worth it for your own education. descriptions on the internet will only get you so far, there is nothing like first-hand experience.

Acetaldehyde can be caused by oxidation during storage as well as fermentation, but it may not be that at all.

 

[Deebo]

Maybe lacto infection?

 

[Nick JD]

Maybe lacto infection?

My guess is acetobacter.

 

[katzke]

Well I have taken 2 classes on off flavors or tastes. I can tell you that not very many of the tasters got all the flavors. I think some were cheating. The ones that were honest were not able to get some of the flavors and were able to get others. I am good at buttered pop corn.

I can say I know when a beer tastes good or not. I can not say exactly what is wrong with the one I do not like. Some of the beers I do not like are correct. I am not a fan of funky yeast and do not like the weird wheat flavors or Belgian flavors like bubble gum or clove. I even go back and forth on citrus hop beers.

So it is good to get more then one tasters advice. One may like or miss identify what you are getting.

 

[brucearnold]

GL, aren't those fault kits about $250 to buy?

Truman,
I believe I had a similar problem with a Boho Pils that I once made. Now I can't tell for certain what the problem was, but from feedback from other club members, I am putting my fault down to not a healthy enough starter, or sitting on the yeast cake too long in the Primary.

Am going to try and scrub some of this flavour through carbing and venting (has been lagering now for an additional 6 months) and if this doesn't work serve it to the swill drinkers at my next BBQ.

 

[Greg.L]

GL, aren't those fault kits about $250 to buy?

I wouldn't be surprised, but you get a lot of use from a kit, so if you can find someone to let you sniff theirs it would help. Some wine clubs or vignerons associations have them. Just a sample of acetaldehyde is very useful, smell it once and you'll never forget.

I was once at a local vigneron's meeting, they were tasting a bottle trying to decide the fault. One sniff and I knew it was acetaldehyde = oxidation. Just because I once had a sniff from a sample in a fault kit.

 

[manticle]

if you can find someone to let you sniff theirs

They have dedicated websites for that very thing.

 

[Muscovy_333]

My guess is acetobacter.

+1 if it is vinegar..ish.
I used to get cider notes prior to temp control.

What yeast strain Truman?

 

[mxd]

brewing anything for 7 days at 14 degrees is a bit quick, it may have finished but you could raise the temp up and a few degrees and give it another fews days to clean up. not too sure what yeast you used but if it was a liquid yeast and you didn't do a starter and only used 1 pack, you'll get some "off" flavours as the yeast is underpited. Did you add brewing salt, what was the recipe, if lots of pilsner then maybe a acid rest was called for in the mash. Unfortunately it's not a precise science, the little yeasties are alive

 

[Wasabi]

Acetaldehyde wouldn't traditionally be described as sour, and for te threshold of most people, it's more a smell than a taste.

That being said, although it is traditionally described as "green apple" i have never perceived it that way. The other two descriptors that come up a lot when i am training are "cut pumpkin" and "paint emulsion", and for me cut pumpkin hits the nail on the head.

Re the tasting kits, Aroxa make great ones and they do some ideal ones for homebrew groups. They are expensive because of the hoops to jump through to make them food grade...plus the purification process is quite a bit of work. I use a mix of aroxa pills and wet chemistry at work.

Beware though of pills that claim to represent Acetaldehyde. Its a very difficult compound to isolate and most pills just use an acetaldehyde like compound. We have given up using the pills and i do all my acet spikes with wet chem. The pills we have run through the mass spec at work have returned concentrations way below threshold.

 

[Truman42]

@MXD...I didnt ferment this brew at 14C for 7 days, that was my first kit beer done back in winter. Ive since upgraded to BIAb and use temp control.

This brew was Pale Malt and Crystal 120, fermented with Safale S-04. Yeast was pitched without a starter at 1.050 and after 7 days I CC'd it for 5 days before bottling. Not sure what my Fg was as I forgot to record it but it was stable over 3 days.

In hindsight I probably rushed it too much (wanted to get it ready by xmas).

I cant really describe the taste although I can tell its not right. Its bloody hard trying to work out what the off flavours are.

I asked my wife if she thought it was green apples and she said yes but not as pungent.

 

[pyrosx]

I asked my wife if she thought it was green apples and she said yes but not as pungent.

My only experience (so far) with the "green apple" smell was with a coopers yeast reculture attempt that was pretty severely mistreated - and if you've ever had a "sour apple warhead" or any one of the other numerous sour apple lollies (those ******* horrible worm starburst things, for example) - the smell is unmistakeable.

If you're not thinking "OMG, apple sour faaaaark" when you smell it, then I don't think it's the same sour apple smell i had.

 

[manticle]

Take it to grain and grape. Most of the staff there would pbe happy to taste and give you their opinion.

I'd offer but the logistics of getting it to me and the probability of me nailing the exact issue might be problematic. Can still have a crack if you want to post a bottle (or save one for a future brewday).

 

[dr K]

Enrol yourself in a BJCP course, you dont have to take the exam but you will learn heaps in particular the sensory skills. Doing the BJCP will not make you a beer judge but it will expand your horizons...

K