Acetaldehyde In Last Few Batches

[Crazy Neighbor]

I'm new to this forum. I've been brewing for about 30 years, but all of the sudden my last few batches have the green apple aroma - acetaldehyde?. I use the Brewfather app for my yeast pitch rate calculator. I brew both ales and lagers and both have had the apple aroma. I ferment in a 3.5 gal Fermonster plastic carboy w/spigot. I have a Thermowell to house my Inkbird temperature probe and use a small freezer for my fermenting chamber. I don't rack to a keg until the gravity has not changed for 7 days which usually means 2+ weeks in the fermenter. I clean with a 2:1 solution of OxiClean/Seventh Generation Powder Dishwasher Powder (both unscented) and do a Clean In Place @ 130º using my pump attached to my Anvil Foundr 6.5. Carboys are cleaned using the same solution using hot tap water. I use StarSan for sanitizing - everything. I am perplexed. Anyone's input is appreciated.

 

[MaxStout]

You're doing a lot of the right things. Good sanitation and temp control.

Are you pitching warm and letting it cool in the fv? What strain of yeast? Is it a highly flocculent strain that drops out before it has a chance to clean up? You could try rousing the yeast a few times along the way during primary fermentation.

 

[Crazy Neighbor]

Sorry, forgot to mention that I use a Scylla immersion wort chiller in my All in One kettle which brings the temp down to 68º within about 10-15 min. Then I transfer to the fermenter where I can pitch ale yeast right away. If a lager, then I bring down to 54º before I pitch. I oxygenate when using liquid yeast with pure oxygen and an Oxywand for 30 seconds @ 1l/minute (I make 2.5 gal batches). Last couple of batches I used S-23 for a Czech style amber lager and Imperial "Dieter" for a Belgian style pale ale. I'm perplexed. Maybe I'll try rousing the yeast.

 

[Bobby_M]

Are you ramping the fermentation temps at the tail end of fermentation a few degrees higher? My ales are fermented at about 66F usually for 4-5 days, then 70F for a few days past FG. Lagers are similar, 55F for a week, then 65F for the remainder. This prevents most Diacetyl and Acetaldehyde problems. Also, try slowing the oxygen rate down and leaving it for 60-90 seconds.

 

[sibelman]

@Crazy Neighbor, gotta ask the obvious question: what's changed? Same recipes and yeasts? Same equipment and process?

 

[Kickass]

I’ve never experienced that off flavor but I’d consider myself an average taster, at best. I may also have a blind spot in detecting it.

Acetaldehyde indicates a fermentation circumstance. One thing I’ve read and routinely practice is to bring the temp up a few degrees towards the end of fermentation. You don’t want the yeast to flocculate, and go dormant before they have a chance to metabolize those fermentation byproducts.

 

[Crazy Neighbor]

@Crazy Neighbor, gotta ask the obvious question: what's changed? Same recipes and yeasts? Same equipment and process?

I’ve never experienced that off flavor but I’d consider myself an average taster, at best. I may also have a blind spot in detecting it.

Acetaldehyde indicates a fermentation circumstance. One thing I’ve read and routinely practice is to bring the temp up a few degrees towards the end of fermentation. You don’t want the yeast to flocculate, and go dormant before they have a chance to metabolize those fermentation byproducts.

Yes, I ramp my temp. I usually wait until I'm 50% complete and then I raise up the temp.

 

[Crazy Neighbor]

@Crazy Neighbor, gotta ask the obvious question: what's changed? Same recipes and yeasts? Same equipment and process?

No changes and that's what got me thinking. As mentioned earlier I clean in place using my version of PBW and 130º water. Then it hit me. I never remove the ball valve and fittings. I took it apart and it was filthy. All kinds of crud. I soaked in my cleaning solution with very hot water and got out some brushes. Now shiny clean. I haven't brewed since I cleaned the valve, but I have to believe that was the culprit. I described it as acetaldehyde, but maybe it was another off aroma/flavor. I will brew, ferment and then post my results. Thanks for all the input.

 

[sibelman]

remove the ball valve and fittings

The annoyance of this cleaning process is why I replaced my kettle's ball valve with a Blichmann "linear flow" valve: easy tool-free disassembly. If I were buying a kettle, I'd probably opt for tri-clamp instead of NPT to make cleaning even easier.

I hope this resolves your "acetaldehyde" issue.

 

[Bobby_M]

No changes and that's what got me thinking. As mentioned earlier I clean in place using my version of PBW and 130º water. Then it hit me. I never remove the ball valve and fittings. I took it apart and it was filthy. All kinds of crud. I soaked in my cleaning solution with very hot water and got out some brushes. Now shiny clean. I haven't brewed since I cleaned the valve, but I have to believe that was the culprit. I described it as acetaldehyde, but maybe it was another off aroma/flavor. I will brew, ferment and then post my results. Thanks for all the input.

When you're cleaning in place, position all your ball valves in the half open position and occasionally cycle them open and closed and then back to half open. that's the only position where the space behind the seats is open to the flow path and it will allow cleaning solution to flush that area. It's not the same as taking them apart and physically cleaning but it's MUCH better than doing it with the valves fully open where that area is isolated. Don't forget to do the same when you're rinsing out the PBW with hot water.

 

[pvpeacock]

I had a similar experience years ago when I was using a Blichmann brew kettle. I was meticulous in cleaning and sanitizing everything, but I never took apart the brew kettle ball valve. When I started to get off flavors, I finally took the ball valve apart and was disgusted with what I found. I ultimately replaced the ball valve with one of these so I could easily take it apart by hand and clean it after every brew day. https://www.brewershardware.com/1-2...lyNeWKeqnpdlhX5bnMmCCgCgD9vopgbvstAy47cQOiqpv I never had the off flavor return.

 

[Crazy Neighbor]

I had a similar experience years ago when I was using a Blichmann brew kettle. I was meticulous in cleaning and sanitizing everything, but I never took apart the brew kettle ball valve. When I started to get off flavors, I finally took the ball valve apart and was disgusted with what I found. I ultimately replaced the ball valve with one of these so I could easily take it apart by hand and clean it after every brew day. https://www.brewershardware.com/1-2...lyNeWKeqnpdlhX5bnMmCCgCgD9vopgbvstAy47cQOiqpv I never had the off flavor return.

Awesome, I will check it out. Thanks

 

[505-Brewer]

Suggestion: Make sure you also have sufficient yeast nutrient. Hope you found the solution!