I recently started brewing and have completed three batches so far (Amber/Pale Ale). However, each batch seems to have that distinct green apple flavor to it. It's gone down a bit with each batch but even as my latest batch conditions I still smell a small amount of it. I've been reading forums and researching possible causes and still can't seem to fix this issue. Here's a summary of the latest batch:

-Grains steeped in 170F and boil done using malt extract.

-Wort aerated with a stirring stick for about five minutes until a thick head of foam appears. OG reading of ~1.050

-Wyeast smack pack is now ready after ~4 hours to get started, pitched in to ~70F wort in a plastic bucket.

-Airlock activity starts ~12 hours later and lasts for ~24 hours before stopping.

-A thick krausen forms and lasts for about a week before settling back down. ~10 days after pitching the FG reads ~1.010. Acetaldehyde smell is present by this point.

-Wort is re-racked to a secondary for conditioning. It's been seven days since re-racking and I'm going to add the dry hops tonight.

What can I do to improve my process? Am I adding enough yeast? Should i use pure O2 for aerating? Would switching to an all-grain brew help? I've been meticulous about sanitizing with StarSan so I don't think sanitization is my issue. Any advice would be welcome, thanks!

  • Pitching at 70F is too high, and racking is unnecessary, although I'm not sure if those contribute directly to acetaldehyde.
    – GHP
    Feb 16, 2016 at 21:22
  • @Graham 70°F is right-on for pitch temperature for most ale yeasts. At least, yeast manufacturers seem to think so. Whether you want to then cool the wort down further for the first few days of primary is another question.
    – sintax
    Feb 20, 2016 at 0:25
  • Many homebrewers really disagree with the temp ranges suggested by Wyeast & White Labs, as those ranges seem more suited to commercial brewing, where higher pressures allow yeast to work hotter without ill effect.
    – GHP
    Feb 22, 2016 at 13:04

2 Answers 2


Acetaldehyde is most often caused by aeration of the wort. I would suggest trying a batch where you do not rack to secondary, as this could be the point in time where the oxidation is occurring. Or you could try purging the secondary vessel with CO2 prior to racking. Also make sure that you have a good solid flow of wort during racking, the introduction of oxygen can occur where your tubing connects to the racking cane if it is not well sealed.

Pure O2, and/or the all-grain process will not improve this. They add complications to the brew process. Get this mastered first.

  • I thought re-racking might have been the issue but the acetaldehyde smell was already present before re-racking.
    – Alex Loper
    Feb 16, 2016 at 21:38
  • Some strains of yeast produce higher amounts of acetaldehyde than others. So you could try another strain. Any chances of hot-side aeration in your process?
    – Jake Bruun
    Feb 16, 2016 at 21:51
  • Do you use a cleaner on your fermenter prior to using Star-San? Something like PBW, or 1-step. It is important to have the vessel clean before sanitizing.
    – Jake Bruun
    Feb 16, 2016 at 21:55
  • The only thing I can think of that would have caused HSA is while pouring the boiled wort into the bucket, though in this case I poured even slower than usual due to the fact I was pouring into some cloth the filter out the floating hops. As for sanitizing, I was using iodine previously to sanitize but I generally clean with soap&sponge (soft side) before sanitizing.
    – Alex Loper
    Feb 16, 2016 at 21:59
  • 1
    I would definitely recommend a cleaning product in addition to the soap & sponge. Beer stone can build up on a fermenter and is nearly invisibile, and this can harbor bacteria. I had this same issue in the past and it was alleviated once I started using PBW. I would also recommend chilling your wort before pouring it into the bucket. Use a ice bath, or pick up an immersion chiller.
    – Jake Bruun
    Feb 16, 2016 at 22:13

What OGs are you pitching a single Wyeast pack into? Those smack packs are for proving yeast viability; they aren't a self-contained sufficient starter for worts over 1.035 (at 5 gallons) or so.

  • OG reading of 1.050. From everything I've read the smack packs are fine for anything less than 1.060 OG though.
    – Alex Loper
    Feb 19, 2016 at 23:54
  • If you're aiming for a million cells per ml per degree Plato, you'd need 2.6 brand-new smack packs fit a 1.050 five gallon wort. brewersfriend.com/yeast-pitch-rate-and-starter-calculator
    – sintax
    Feb 20, 2016 at 0:04
  • So it is. Would making a starter from the smack pack help this? Or does the starter need to come from the spent yeast in the fermentation bucket?
    – Alex Loper
    Feb 20, 2016 at 0:18
  • @AlexLoper Making a starter from the smack pack is the usual solution. Just start with a liter or so and step up a couple of times to half a gallon ish and you should be in much better shape. Don't worry about fancy stir bars and plates, just swirl a covered mason jar a couple times a day. You should be able to Google for a number of good complete guides to making starters.
    – sintax
    Feb 20, 2016 at 0:20

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