Frustrated with green apple flavor

[50calguy32]

Hello

With the past half-dozen brews I had really strong green apple flavors in them. I've aged them for months in the fridge, at room temperature, and even on the yeast cake for a month, but there is always green apple flavor. It never goes away.

The beer ferments in a temperature controlled chest freezer at 68°. I've use dry and liquid yeast, I watch my pitching temperatures. I believe I am sanitizing everything correctly.

Anybody have any ideas?

 

[ny101]

I'm thinking 1 of 2 things.... 68 sounds pretty high. If your fermenters are anything like mine they get 6-8 degrees warmer in the center than the side, so your brew may be getting pretty warm. Most times when the yeast manufacturer calls for 65-68 I set my fridge to 63.

Also, are you leaving your beer on the yeast long enough? Yeast actually cleans up the primary flavor associated with green apple during fermentation (if there isn't way too much).
I like to leave my beer on the yeast for 1 week following terminal gravity.

I'm thinking the temp issue is creating too much aceldehyde and the aging issue is not allowing the yeast to clean it up.

 

[50calguy32]

Thanks for the reply ny101. I do let my beer sit on the yeast for at least 3 weeks. I will lower my freezer temp to 63 and try that. thanks

 

[billl]

That is generally an indication of stressed yeast. How much are you pitching and how are you oxegenating?

 

[unionrdr]

Are you moving the beer off the yeast in primary to clear? This flavor is usually caused by not enough time to clean up after FG is reached from higher than desirable ferment temps. some have said it can be caused by adding too much sugar to the recipe as well.

 

[TheZymurgist]

I'm thinking 1 of 2 things.... 68 sounds pretty high. If your fermenters are anything like mine they get 6-8 degrees warmer in the center than the side, so your brew may be getting pretty warm. Most times when the yeast manufacturer calls for 65-68 I set my fridge to 63.

Also, are you leaving your beer on the yeast long enough? Yeast actually cleans up the primary flavor associated with green apple during fermentation (if there isn't way too much).
I like to leave my beer on the yeast for 1 week following terminal gravity.

I'm thinking the temp issue is creating too much aceldehyde and the aging issue is not allowing the yeast to clean it up.

That is generally an indication of stressed yeast. How much are you pitching and how are you oxegenating?

Both of these. Make sure you're not fermenting too hot, although I've done plenty at 68* ambient temp, and not had a problem. Could be the type of yeast you're using, though.

Also make sure you're pitching enough yeast and oxygenating the wort plenty. IMO, the three best pieces of equipment a brewer can have are fermentation chamber, stir plate, and O2 tank with an air stone.

 

[Homercidal]

IMO 68 is too warm for Nottingham yeast. I definitely tasted some fruityness when I fermented that warm with it in a pale ale. And that was in a temp controlled fridge. Kind of disappointing, but I did drink it all...

I would double check the pitch rate and O2 levels and make sure they are right. And maybe try and ferment your yeast even cooler. There are other strains that give more esters than others.

 

[PDX_T]

green apple is from acetaldehyde. it's a precursor to ethanol formation, it should go away with bulk aging, but it can also be formed when finished beer is exposed to oxygen. the process is reversible as long as the yeast are still somewhat active. sounds like you're bottling too early or getting too much oxygen in at some point.

 

[50calguy32]

Thanks for the info guys.

Ive brewed a blonde, bel wit, porter and IPAs, they all had it. I do use an air stone and O2 bottle. I mostly use safale 05 yeast. I usually brew 2.5g and use a whole yeast pack, so could I still be under pitching? I have let the beer age on the yeast cake for months, but that still didnt help.

Can an infection cause this flavor?

 

[billl]

Yes. Some wild yeast and certain bacteria can cause a sour apple flavor. They aren't the most likely cause, but it could be.

 

[duboman]

General and most common causes of Acetaldehyde:
1. Early removal from yeast
2. Early/premature flocculation of yeast
3.Oxygen depletion
4.Bacterial spoilage
5. Oxidation

If you are pitching an entire package of yeast for a 2.5 gallon batch the over pitching may be stressing the yeast and preventing them from doing their cleanup job. Over infusing with O2 can also cause issues. It sounds as though something in your pitching and fermentation process is stressing the yeast to the point that they are not capable of cleaning up after themselves.

 

[TheZymurgist]

General and most common causes of Acetaldehyde:
1. Early removal from yeast
2. Early/premature flocculation of yeast
3.Oxygen depletion
4.Bacterial spoilage
5. Oxidation

If you are pitching an entire package of yeast for a 2.5 gallon batch the over pitching may be stressing the yeast and preventing them from doing their cleanup job. Over infusing with O2 can also cause issues. It sounds as though something in your pitching and fermentation process is stressing the yeast to the point that they are not capable of cleaning up after themselves.

I doubt over-pitching is the issue. I've never heard that over-pitching could cause the production of acetaldehyde, but I could be wrong. I'd say the most likely factor in his case would be fermentation temperature.

Most likely, with 2.5 gallon batches and an entire packet of dry yeast, you're not under-pitching, but it all depends on the OG of your batches. Going by the general style guidelines of the styles you listed, I would venture to guess you're pitching a proper amount of yeast, but that assumes you're not making anything with a high OG.

Even if you let the beer sit on the yeast for months, once they're dormant, they're done. If fermentation temperature is causing a high amount of acetaldehyde production, they may not have the ability to clean all of it up. Try setting your freezer on 64* for the first couple days, then ramp it up 1 or 2 degrees per day until fermentation is complete. That should help.

 

[Spartan1979]

My neighbor was having this problem. I finally figured it out. He got an aeration kit and was aerating right before kegging! I explained that he should be aerating right before pitching the yeast and his beers are much better!

 

[hardrain]

General and most common causes of Acetaldehyde:
1. Early removal from yeast
2. Early/premature flocculation of yeast
3.Oxygen depletion
4.Bacterial spoilage
5. Oxidation

[...]Over infusing with O2 can also cause issues.

I doubt over-pitching is the issue. I've never heard that over-pitching could cause the production of acetaldehyde, but I could be wrong. I'd say the most likely factor in his case would be fermentation temperature.

Old thread time. I've noticed the recurrence of the same apple flavor (I get more of a brown apple, or weak apple juice, but it's somewhat 'green', the most common description of acetaldehyde) in a lager, saison and pale ale.

I've just recently started pitching 2L starters with a stir plate into 5.5G batches, plus doing 1-1.5 minutes of pure O2 after chilling and before pitching. Most beers are ~1.050, lightly hopped. The only one I didn't notice the apple flavor on, interestingly, was 1.061, heavily hopped, and (for some reason) I only did ~45 seconds of O2.

Before this I was pitching a single 100B package directly and splashed the beer to get O2.

My theory is the combo of over-pitching plus excessive O2 is doing one of two things:
1. The overpitching and O2 are rapidly increasing yeast population, to the point of being seriously overpopulated, causing the yeast to drop out well before cleaning up the acetaldehyde.

2. Someone with more of a science background needs to tell me if this is even possible, but maybe(?)...the yeast are using the O2, but not all of it, and because of (totally guessing here) population a portion of the yeast are making ethanol before depleting 100% of the O2...the only other cause of this flavor that's possible as far as I can tell is oxygenated ethanol. This isn't my understanding of how yeast work but with extremes maybe it's possible?

It's not: temperature (I do the swamp + chest freezer, and measured internal temp on last two, ales internal at ~62-65F, lager 50-55F), infection (process is good, and flavor doesn't change over time or have any sour notes at all), early removal of yeast (2 weeks for ales, 3 for lager, and lager included a 3-day rest at ~67F).

...I've taken a couple of the beers out, warmed and shook them, and I'm curious if there is enough yeast to clean up the acetaldehyde. I'm also curious to brew the same beer again with only a portion of the starter yeast and way less O2 (I'm thinking of dialing back to ~15 seconds to start).

It took me a while to even come up with this as a guess given the rampantness of which people post the impossibility of overpitching, but maybe in combination with O2 it's a very legitimate thing.