Author Topic: Safale US-05 - American Ale Yeast has banana off flavors...  (Read 4471 times)

Offline obwahine

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This was my first batch ever.  Decided to go with a west coast pale ale that seemed simple enough. 

I placed the carboy in a container of water in a dark closet and initially put frozen bottles.  Ambient temp of the house never go above 70 degrees during fermentation.  The thermometer that I placed in the water to monitor temps broke and and started reading 80+ degrees.  Just by touch alone I could tell the water was not 80 degrees.  It felt much cooler than the air temp even when the ice bottles melted, so I figured it would be fine to not switch out the bottles and just let the carboy hang out in the closet for the duration of fermentation.  Everything seemed to go accordingly and I bottled it seven days ago.  I popped one in the fridge and later tasted it last night to test carbonation.  And all I could taste were these overpowering banana notes. 

After some research I saw that this taste could be a result of esters that formed because the fermentation temp was higher than ideal.  I also read elsewhere that as the beer bottle-conditions, these banana notes could possibly diminish.       

So my questions are:

Do you think it was the production of these esters that caused the banana flavor?

Will the flavor in fact diminish as the beer bottle-conditions?

When fermenting, is it better for the beer to be a little colder as opposed to a little warmer?  i.e, When my thermometer broke, should I have just kept switching my frozen bottles out every 12 hours just to be safe regardless of what the ambient temp of the house was?

Thank you for your advice! 

Offline tommymorris

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #1 on: May 29, 2016, 10:17:06 PM »
The banana flavors are definitely from the yeast. The flavor is from esters produced by the yeast from stress. Stress can be from high temperature or too little yeast. Probably temp. It is best to lower the temp of the beer, not the water or environment, to low to mid 60's, before you add the yeast. Esters are released by yeast in the first 24-72 hours.

The banana flavor may fade a bit but it likely will not. I often get off flavors when tasting a very early sample (hydrometer) that then fade. If the flavor is still there after carbonation in a bottle it's probably gonna stay.

For us-05 it's better to steer low on the temp. Us-05 and its liquid cousins can ferment in the low 50's.

Offline obwahine

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #2 on: May 29, 2016, 10:38:28 PM »
The banana flavors are definitely from the yeast. The flavor is from esters produced by the yeast from stress. Stress can be from high temperature or too little yeast. Probably temp. It is best to lower the temp of the beer, not the water or environment, to low to mid 60's, before you add the yeast. Esters are released by yeast in the first 24-72 hours.

The banana flavor may fade a bit but it likely will not. I often get off flavors when tasting a very early sample (hydrometer) that then fade. If the flavor is still there after carbonation in a bottle it's probably gonna stay.

For us-05 it's better to steer low on the temp. Us-05 and its liquid cousins can ferment in the low 50's.

I re-hydrated the yeast (I now know that this is not particularly necessary, even with dry yeasts).  It said to boil the water, let it cool and then add the dry yeast to re-hydrate it before adding it to the wort.  I *might* have been a little eager and I *might* have added the dry yeast to the water before it cooled completely to room temperature.  Do you think that these esters could have been released as early as the re-hydrating phase? 

Offline tommymorris

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Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #3 on: May 29, 2016, 10:43:33 PM »
The banana flavors are definitely from the yeast. The flavor is from esters produced by the yeast from stress. Stress can be from high temperature or too little yeast. Probably temp. It is best to lower the temp of the beer, not the water or environment, to low to mid 60's, before you add the yeast. Esters are released by yeast in the first 24-72 hours.

The banana flavor may fade a bit but it likely will not. I often get off flavors when tasting a very early sample (hydrometer) that then fade. If the flavor is still there after carbonation in a bottle it's probably gonna stay.

For us-05 it's better to steer low on the temp. Us-05 and its liquid cousins can ferment in the low 50's.

I re-hydrated the yeast (I now know that this is not particularly necessary, even with dry yeasts).  It said to boil the water, let it cool and then add the dry yeast to re-hydrate it before adding it to the wort.  I *might* have been a little eager and I *might* have added the dry yeast to the water before it cooled completely to room temperature.  Do you think that these esters could have been released as early as the re-hydrating phase?
I don't think the esters came from rehydration. I don't think the yeast is reproducing at that stage.

I believe the rehydration instructions say to rehydrate yeast at 90F. I don't think 90F would hurt. If by impatient you mean significantly warmer you could have killed a lot of the yeast cells and then ended up under pitching. I think (not entirely sure) that to kill the yeast the rehydration water would need to be >140F.

Bottom line, I don't know for sure.
« Last Edit: May 30, 2016, 05:24:51 PM by alestateyall »

Offline santoch

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #4 on: May 30, 2016, 01:55:54 AM »
no, the esters (isoamyl acetate is what give the banana flavor) formed during warm fermentation, not during rehydration.  They need sugars in order to produce any outputs.  Rehyrdration simply re-wets the yeast cells and allows the cell wall to become permeable again.

Fermentation is exothermic.  In other words, it creates heat.  The beer temp is often several degrees above ambient, so if your chamber got up to 80, your beer was even higher.

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Offline obwahine

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #5 on: May 30, 2016, 05:57:31 PM »
no, the esters (isoamyl acetate is what give the banana flavor) formed during warm fermentation, not during rehydration.  They need sugars in order to produce any outputs.  Rehyrdration simply re-wets the yeast cells and allows the cell wall to become permeable again.

Fermentation is exothermic.  In other words, it creates heat.  The beer temp is often several degrees above ambient, so if your chamber got up to 80, your beer was even higher.

HTH-

Thank you! I probably would have known this had I placed a sticker thermometer on the carboy, but one was never placed in the kit we purchased and since i'm impatient and wanted to brew before we got one, I figured I could just use the stick thermometer to keep an eye on the water that the carboy was in.  Since that thermometer broke, I was just testing the ambient water with my hand.  Now, because of you guys, I know that the temperature of the beer is often higher, and therefore I need to measure it instead in order to keep it at the correct temp. 

We have since bought a ticker thermometer that attaches to the side of the carboy.

Now my question is this:   When the carboy is placed in the bucket of water, shouldn't we fill the bucket to so the water is level with he fermenting beer that's inside?  In my mind, this would allow for equal temperature regulation.  But if I do that, then the sticker thermometer that I place on the outside of the carboy to measure the temp of the beer will also be submerged in the ambient water.  How do I get an accurate reading of just the beer, since that is what I should be most concerned about? 

I know these questions must be so mundane, but as a beginner, the answers are extremely helpful!  I've learned so much already!     

Offline denny

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #6 on: May 30, 2016, 06:00:06 PM »
Now my question is this:   When the carboy is placed in the bucket of water, shouldn't we fill the bucket to so the water is level with he fermenting beer that's inside?  In my mind, this would allow for equal temperature regulation.  But if I do that, then the sticker thermometer that I place on the outside of the carboy to measure the temp of the beer will also be submerged in the ambient water.  How do I get an accurate reading of just the beer, since that is what I should be most concerned about? 

I know these questions must be so mundane, but as a beginner, the answers are extremely helpful!  I've learned so much already!   

I went through that same decision.  Having the water a little lower isn't gonna affect things much. 
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Offline HoosierBrew

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #7 on: May 30, 2016, 06:07:55 PM »
I used to struggle with that, too. FWIW I finally went the other way and filled the tub until the bucket almost floated (more water equaled more thermal mass in my mind) and just focused on controlling the water temp with frozen bottles, checking the water with my thermometer. Both ways worked well for me.
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Offline charles1968

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #8 on: May 31, 2016, 05:42:14 PM »
Having tried the bucket of cold water & ice bottles method a lot, I think it's much less effective than simply placing the fermenter next to a large ice bottle inside an insulated container such as a 4-season sleeping bag, with no water bucket. lowers the temp of the wort VERY effectively and then holds it steady for about 2-3 days before you need to swap in a new ice bottle. By that time fermentation is more than halfway finished. Stick-on thermometer is a great help.
« Last Edit: May 31, 2016, 05:44:04 PM by charles1968 »

Offline obwahine

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #9 on: May 31, 2016, 11:18:43 PM »
Having tried the bucket of cold water & ice bottles method a lot, I think it's much less effective than simply placing the fermenter next to a large ice bottle inside an insulated container such as a 4-season sleeping bag, with no water bucket. lowers the temp of the wort VERY effectively and then holds it steady for about 2-3 days before you need to swap in a new ice bottle. By that time fermentation is more than halfway finished. Stick-on thermometer is a great help.

Huh!  I never would have thought about trying this.  Any other ideas to jerry-rig a cool environment for the yeast without having to build something out of a fridge?     

Offline BrewBama

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #10 on: June 01, 2016, 12:09:53 AM »
That's the beauty of this forum: These guys know everything and share the information freely. Stick around - if you do you will make better beer.


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Offline charles1968

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #11 on: June 01, 2016, 12:15:29 PM »
Huh!  I never would have thought about trying this.  Any other ideas to jerry-rig a cool environment for the yeast without having to build something out of a fridge?   

Google "mother of fermentation chamber" if you want an elaborate project. It's essentially a home-made fridge made out of polystyrene. A sleeping bag is easier and will lower the temp enough to make lager.

For keeping ales cool in summer I use a 2-litre frozen water bottle  placed next to the FV in an Ikea shopping bag, with the shopping big sitting inside a 4-season sleeping bag. For lager, use two frozen water bottles. The plastic shopping bag keeps condensation off the sleeping bag. A stick-on thermometer allows you to keep the temperature within a narrow range.




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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #12 on: June 01, 2016, 01:33:47 PM »
I'm planning on finally building the "Son of Fermentation Chiller" this week or next. I have an STC-1000 and the computer fan plus a piece of 2" foam board.

Offline brewinhard

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #13 on: June 01, 2016, 01:55:35 PM »
I'm planning on finally building the "Son of Fermentation Chiller" this week or next. I have an STC-1000 and the computer fan plus a piece of 2" foam board.

I understand that people like to build things for brewing, but why not just look for a cheap (if not even free) fridge to use for a fermentation chamber?  It will save you time to brew more and better beer. Just my 2 lazy un-engineering sense.

Offline Hand of Dom

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Re: Safale US-05 - American Ale Yeast has banana off flavors...
« Reply #14 on: June 01, 2016, 02:02:27 PM »
I'm planning on finally building the "Son of Fermentation Chiller" this week or next. I have an STC-1000 and the computer fan plus a piece of 2" foam board.

I understand that people like to build things for brewing, but why not just look for a cheap (if not even free) fridge to use for a fermentation chamber?  It will save you time to brew more and better beer. Just my 2 lazy un-engineering sense.

That's what I did, fridge for £10 from a recycling centre (needed a new thermostat, which they bypassed for me), and an Inkbird controller for £25. 
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