Aerating wort causing sour beers?

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DontDrinkAndDrum

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I'm about to brew the first batch that I've made in quite some time, but I'm a bit nervous about it. The last two batches I made, a red and a brown ale, came out sour, whereas the previous two batches, a red ale and an IPA, came out just fine. The only variation in procedure I made was that I aerated the wort with a sterilized whisk before adding the yeast on my last two batches.

Now, i know that the only time that it is good to have air induced into the concoction is before primary fermentation occurs, because it can allow the yeast to get to the fermentables before any bacteria does. What i'm wondering is if aeration can also cause undesirables to get at the wort faster, which is the variation in my procedure that is causing my brew to sour.

any thoughts?.....
 
Are you aerating the wort hot or at pitching temps? I was told by my LHBS that you do not want to do this while it is hot. I can cause some off flavors. For the life of me, I cannot remember the science behind it.
 
DontDrinkAndDrum said:
i was aerating at pitching temps, right before pitching the yeast

That should not cause any off flavors...this is good.

When someone says sour I think infection. Another flavor that I might describe as sour is an off flavor you can get from old liquid malt extract.
 
well all the recipes i've used thus far are boxed kit beers assembled by the store i buy them from, so i'd like to think/hope they don't put old LME in their kits.

i looked on the can of LME i'm about to use, and i didn't see anything along the lines of an expiration date printed on the can. I suppose the manufacturers don't expect the stuff to go bad.

I just thought of something else too...could some sort of infection of the wort occur during cooling before adding wort to the fermenter? say, if cooling takes too long.
 
Your yeast need the oxygen in solution for proper attenuation/complete fermentation so I doubt that is the cause unless you are getting a bacterial infection at the same time. I would pay extra attention to your sanitation and any nooks, cracks, ect where bugs could be hiding in your gear that the beer comes in contact with.

Is the flavor definitely sour or could it be another common off flavor?
 
If it is a lacto or aceto infection, the sourness will get worse pre-bottle. You'd notice a definite increase in sourness. Iirc, they both need O2 to thrive so once bottled the clock starts ticking against them, which is why I say pre-bottle. There will also be evidence (usually as aceto forms 'ropy' looking things in the wort, brett and some others form a pellicle). A lacto infection will be distinctly sour, I mean sour. Not just a 'hint'.
 
Yeah, everyone here is spot-on. I know that sour taste. It is the taste of...extract. Malt extract.

Move on to Partial Mash as soon as possible.

Oh, and...drop your fermentation temps down to the lower range of whatever yeast your using. That also helps. The higher the fermentation temps, the more ester production, which can turn sour after awhile in my experience. My beers got much better when fall rolled around.

Lastly, get some kind of mechanical oxygenation or aeration kit. I use a $30 aeration kit from AHS, but oxygenation is the way to go if you can swing it. This is much quicker and reduces the chance of infection (my kit has an inline HEPA filter).
 
Evan! said:
Yeah, everyone here is spot-on. I know that sour taste. It is the taste of...extract. Malt extract.

Move on to Partial Mash as soon as possible.

Or buy your extract elsewhere.....

Never had any of my extract beers described as sour or experienced off flavors.
 
I too think that its an infection. These are all good suggestions but one I would like to add is maybe making a yeast starter. This should get your brew started faster and closes the window a little on an infection.
 
Evan! said:
Yeah, everyone here is spot-on. I know that sour taste. It is the taste of...extract. Malt extract.

Move on to Partial Mash as soon as possible.

Or use DME.

I haven't changed anything about the way I sanitize...have taken as long or longer to cool the wort since I got away from LME and have not had that taste again.

Sometimes the LME flavor can be described as a "twang" or molasses or licorice. I have had it in what I thought was fresh LME...it might just depend on the manufacturer or how it is handled.

Although I have never had an infected beer, it seems to me that it would taste really bad and since the bacteria can usually consume sugar that the yeast can't it would taste very dry and you might have bottle bombs.
 
One would think LME is usually 'new enough' but there was just a post on here last week about a guy opening a can of LME and the whole top was a layer of thick mold.

obviously something got into the can at teh factory and took hold while it sat on the shelf. it happens.
 
well i don't really have anything to compare it to, i would think it would be called sour, but i wouldn't know how else to describe it. i guess it'd be more tart than sour, not unbearable, but it definitely makes it less enjoyable

come to think of it, i might describe it more as estery...i've had some trappist beers, and that's how the taste of some of them seems to be described, although in my brew it's a lot more mellowed and totally unwanted for the type of beer i'm making
 
does all ester production occur only or mostly in the primary fermentation, or can it carry over into the secondary, and would it be beneficial to transport the beer to cooler temperatures (not cold, just cooler) after primary fermentation?
 
Secondary fermentation is a myth. It's a secondary vessel/bright tank. (Clearing vessel) The majority/all of the fermentation takes place in the primary
 
i understand that the use of the term "fermentation" when referring to secondary fermentation is a bit of a misnomer, but what i'm wondering is if any sort of flavors are or can be produced when in a clarifying vessel (aside from dry hopping, of course)
 
As Orfy says, there really is no such thing as secondary 'fermentation' -- it is a commonly used misnomer. What is really meant is conditioning, which could happen in the primary or secondary vessel.

The conditioning process is very valuable, though. After fermentation is complete, the yeast switch to metabolizing other materials in the beer. Some are by-products, such as diacetyl and acetaldehyde (common off flavours in 'green' beer). They might also reduce some of the strong-flavoured esters in the beer, helping to mellow out the taste. [To answer your questions, yes esters are produced at the begging of primary fermentation and are reduced in the conditioning phase.] During conditioning, other compounds (e.g., tannins) will also gradually settle out, further increasing the quality of the beer.

If you move your beer to cold storage immediately after fermentation is complete, these processes will still happen, but it will take a lot longer, particularly if all the yeast begin to flocculate out of suspension before they have a chance to reduce the by-products that cause off-flavours. I think most beers (particularly high gravity and/or very dark beers) really benefit from a month or more of volume conditioning in a secondary vessel. Fermentation temperature or slightly cooler is probably best.

Cheers! :mug:
 
Evan! said:
oxygenation is the way to go if you can swing it

I completely disagree.

With oxygen it's possible to put in too much oxygen and oxidize your wort (something you don't want to do) and something you don't have to be concerned with using air.

I'll get my brew books out and look up more detailed info if you'd like. I think it's in John Palmer's "How to Brew".

Furthermore air is free, oxygen is not so you'll spend more money to oxygenate that to aerate.

Most all air or oxygen users filter the gas so no difference there unless you use medical O2 and you'll pay thru the nose for that unless you have a free source or steal you grandma's O2 tank.

I have both types and a couple of minutes aerating vs 30 second of oxygenation is not a big deal. But when I was just starting out I let the Local Homebrew store salesman convince me to go with O2 rather than air. Big mistake and waste of money so I try to help others learn from my mistakes. But if you want to go with
O2 I'll sell you mine.
 
I'll throw in another opinion to balance abracadabra's [sorry ab -- don't mean to argue at all!!! :) ]:

I love my O2 system. Yes, over-oxygenation is a potential problem. But it is probably a lot like the issue of over-pitching yeast -- it can happen, and when it does it might lead to off-flavours in your beer. But in practice, it is very hard to do.

Here is a good article from BYO that discusses the risks of over-oxygenating. The take home message is that there are lots of unknowns about what levels of O2 are 'risky', but that it is probably nothing for the homebrewer to worry about.
 
FlyGuy said:
I'll throw in another opinion to balance abracadabra's [sorry ab -- don't mean to argue at all!!! :) ]:

QUOTE]

Don't be sorry, different opinions just like variety are the spice of life and it's good to have different opinions posted.

I don't take offense to differing opinions unless the person is hateful, rude, or calls my character or personality into question.

I often post different opinions just to make for lively discussion or to give the OP and others something to think about.

And I agree that oxidation is not a huge concern just a potential.

But if someone is new or on a tight budget & trying to get the gear they need
O2 is more expensive and a continuing expense where air is not. And I don't think O2 is a better option based on my experience with both types. But hey it's just an opinion and like nose's most everybody has one.:mug:
 
abracadabra said:
Don't be sorry, different opinions just like variety are the spice of life and it's good to have different opinions posted.

I don't take offense to differing opinions unless the person is hateful, rude, or calls my character or personality into question.

I often post different opinions just to make for lively discussion or to give the OP and others something to think about.

And I agree that oxidation is not a huge concern just a potential.

But if someone is new or on a tight budget & trying to get the gear they need
O2 is more expensive and a continuing expense where air is not. And I don't think O2 is a better option based on my experience with both types. But hey it's just an opinion and like nose's most everybody has one.:mug:
I definitely agree that the O2 systems are not cheap -- particularly when compared to an aquarium pump system for aerating. Honestly, I have no idea why they charge so much for them. So yes, they are definitely an expensive add-on to the hobby that isn't a requirement. (But I still love mine for the convenience.)
 
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