Off flavor from time to time

[Mark_]

Hey folks,

Reason for post
I have really been trying to nail down my consistency between batches and am experiencing a sort of off taste/smell with a few batches.

The smell is a little fruity, not really banana, and only happens from time to time. I have made the same recipe three times now with differing results.

My environment:

Recipe: BierMuncher's Centennial Blonde
Brew Type: Full grain
Yeast: S-05
Ferm temp: 66 degrees as measured by the Johnson Controls lead sealed to the ferm bucket inside my ferm chamber

10 gallon igloo MLT, standard brewing equipment, nothing special.

**sidenote** So the first batch I ever made that had this off flavor was BM's Cream Ale. I have not made this one twice.

The first batch of the Centennial Blonde that I made with a swamp cooler was perfect. I made it again several months later, with my new ferm chamber setup, a GE freezer with a Johnson Controller, and it had this fruity taste. It isn't a bad taste, just off.

Fast forward to yesterday and I bottled another batch only to smell the same thing, and also, a sample taste before carbonating has a hint of the taste.

In short:
Cream of three Crops: no temp control, fruity taste/flavor
Centennial Blonde: Swamp cooler temp control (At around 66F), no fruity flavor
Centennial Blonde: Full fermentation temp control,fruity taste/flavor
Centennial Blonde: Full fermentation temp control,fruity taste/flavor

The burning question
Could I be fermenting this too low at 66F? I thought this was a good temp for S05?

I have brewed about 12 batches so far this year and these three have been the only "off batches" thus far. Pale Ales, Milk Stout, Wheat, even a Centennial Blonde have all come out fantastic with the same yeast at the same temperatures.

Again, it isn't bad and I am drinking it but it just seems off.

Any thoughts?

 

[Zamial]

66F seems pretty hot. Fermentation can be 5F warmer than the ambient temp (even in a cooler). I would make the same recipe and crank the temp down to 61F.

Fruity is almost always esters. These are almost always because of to high a ferm temp in the 1st 72 hours.

 

[Mark_]

66F is measured by having a temperature probe sealed via styrofoam against the side of the fermentation bucket. It isn't the ambient temperature. Would you still consider that too warm?

 

[Zamial]

66F is measured by having a temperature probe sealed via styrofoam against the side of the fermentation bucket. It isn't the ambient temperature. Would you still consider that too warm?

IMHO that is closer to ambient temp than fermentation and may even be some shade of in between at best. The thermals created by the yeast would be in the center of the fermentor not the side/edges.

If I was chasing a fruity ester-like flavor I would sure try lowering the temp to see if that solves the issue.

Also are you pitching the correct amount of yeast? Under/over pitching can also effect yeast stress, which can lead to off flavors you are describing as well.

 

[Rivenin]

i would get a fermometer, i think the max temp for s-05 is 72*? IIRC.
it will release some bit of fruit to it at times at high enough temps.

 

[RM-MN]

Since you have the fermentation chamber, turn the control down to 62 for the first 4 days and then pull the fermenter out and let it naturally rise to room temperature. I'll bet your fruity flavors are gone.

 

[BradleyBrew]

I would do this:

- try to insulate the probe against the bucket. I use 4 papertowels folded together into about a 4" x 2" rectangle. Place the probe against the fermenter and then put the paper towels over the probe and tape that up real tight.
- I know it probably doesnt matter but if you dont I would rehydrate the yeast.
-Make sure you pitching temps are good.

I personnally dont think 66 is to hot for S-05. Good luck!

 

[Mark_]

Some good points, thank you!

So several comments.

My last batch I rehydrated the yeast but hadn't before.

The thermometer is sealed very well from the ambient air so I am pretty certain it is reflecting the wort temp at the outside edge.

I think my best bet is to lower the temps as was stated here and see what happens. I guess I'm not doing anything glaringly incorrect!

Thanks everyone! I'll give it a whirl!