Sour Green Apple Taste In Beer

I popped open my fermentor to scoop in a little sample and see how my beer was coming along… I was expecting a nice mildly hoppy pale ale, but the moment I whiffed the beer, I noticed a green apple smell…

It was almost like fresh cut apples, but kind of sour smelling…

Not cool…

Not knowing any better at the time, I transferred the beer to a secondary fermentor and ‘hoped’ the beer would get better there…

Well, turns out that was the biggest mistake I could have made… a whole brew day and 3 weeks of anxiousness only to find that yes in fact, my beer is ruined…

The beer did mellow out a bit, but it was still not what I wanted to drink…

… and here’s the thing… the green apple taste in beer comes from a fermentation by-product… it is a flavor developed as yeast ferments sugars and turns it into alcohol…

Somewhere in the middle of the conversion of sugar to alcohol, green apple flavors develop, but they go away as the beer matures… when the beer is just done fermenting the beer is called ‘green beer’… also known as ‘young beer’…

After the yeast are done fermenting the beer, they go back and ‘clean up’… so all these weird flavors developed during fermentation go away as the beer conditions…

Before I knew much on how to brew beer, I would transfer my beer to a secondary fermentor not knowing any better… I was just basically listening to others who apparently had been brewing this way for years and have had great results…

Well after tons of research, I’ve found that it is often times better to leave the beer in the primary instead of transferring it to a secondary… because the yeast ‘clean up’ the beer… if you remove the beer from the majority of the yeast, then there will be less cleaning up done by the yeast…

Now as far as the sour smell and taste… although it can sometimes be from ‘green beer’, it usually is from either lactobacillus or acetobacter, which are bacteria that produce lactic acid and acetic acid respectively…

This is mainly due to lack of cleaning and sanitizing…

But I’ll tell you… I thought my cleaning and sanitizing was really good until I learned about the different types of cleaners and why you need to use high alkaline cleaners for some types of gunk in home brew equipment and caustic cleaners for other types of gunk…

So all that scrubbing, washing and rinsing I did was virtually useless because I wasn’t using the right cleaners…

Until you learn how to never be the brewer getting sour or green apple tasting beer, you may as well go to the store and pick up a six pack of the cheapest beer just to remind yourself why you started home brewing to begin with… if you are like me, it was to drink better tasting beer than the cheap beer at the stores…

Of course I failed miserably when I first started, but I’ve learned how to improve my brewing and I know you can do so too…

4 Comments

  • Jason

    Reply Reply January 19, 2011

    Definitely agree that opening the fermenter to check on the status and finding the beer to taste like green apples (acetylaldehyde) means its too young. You are correct that racking early would stop the cleanup process.

    However, there are other reasons too. High fermentation could cause yeast to throw out some weird alcohols that taste apple-like. I had that happen to me once before I knew of the importance of fermentation temp control.

    Another reason is yeast strain. Some strains will produce that flavor. For example, US-05(dry) will produce some peach-apple esters that take (no joke) 3-4 weeks to clean up.

    I doubt you have an infection as other symptoms would be present. Also, a major sign of contamination is the taste/smell gets worse over time.

    J

    • Jorge

      Reply Reply January 19, 2011

      @Jason – Hey, glad to see you visiting my blog…

      anyways… good observation on the temperature…. Fusel alcohols make it harder for yeast to clean up…

  • Mathieu Frechette

    Reply Reply April 9, 2013

    I suggest to transfer the young beer to another vessel to avoid autolysis from the dead yeast cells. But if you separate the beer from the yeast cake too early, the remaining yeast may not be able to convert the remaining acetaldehyde to ethanol and your beer will have this green apple taste.

    • Jorge

      Reply Reply April 9, 2013

      Yeast companies have come a long way and autolysis is not an issue… you can leave the beer sitting on the yeast cake longer and not have to worry about it… and yes, you don’t want to move the beer too early…

      Cheers!

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