[quote=“Mroberto1010”]First batch ever fermenting… Irish Red Ale… 16 days in… checked tonight and it has a slight banana smell and still has some yeast floaties on top…
I might have pitched yeast at first a little warm, but then brought temps down to mid to low 60’s… Yesterday brought fermentation temps up to 68 degrees…Plan on bottling this Sunday.
Am I in trouble with the banana smell or will this start to disappear over the next 5 days and in bottles for a couple weeks? Should I leave temps around 68-70 degrees? Anything else?
Cheers :cheers: [/quote]
#1) Do not plan on bottling until you know what is happening here. So it is good you reached out firstly.
#2) Banana odor/ taste is a byproduct of yeast and can be strain/ temp/ process related (such as O2/ lack of in the wort, pitch count, viability etc…) It is one in the same of a family of VDK which yeast produce naturally. Some other of note would be Diacetyl(butter), Acetaldehyde(green apples). The actual VDK attributed to banana faults is called Isoamyl Acetate. Most ale strains do create some low levels of IA and that is where some fruity notes come from along with a couple other VDK that create “fruity” notes also. There are some ale strains that create very little to no IA such as very clean/ neutral yeast like “regular” American/Cali ale or the majority of lager yeast although there are a couple of those that produce IA also. See:
http://www.whitelabs.com/yeast/wlp001-c ... s=homebrew
#3) This goes back to the reason and now explanation for #1. When a beer is going through primary yeast create ethanol along with VDK as a natural byproduct. Levels of VDK can vary depending on actual strain/ conditions. Now, here is the important point below.
#4) After ferment hits terminal SG the yeast re uptake VDK for a period of time. So that is why it is advised to leave the beer on the main yeast cake for 3-7 days after hitting terminal to allow this process to complete and like you indicated allowing the temp to rise at this time is actually an advantage to this process. If you are in a rush and bottle to soon you can arrest this “scrubbing” activity and leave elevated levels of many VDK in the finished beer.
So bottom line is give it some time (like the 5-7 days you stated… I would go 7 at the elevated temps just to ensure full reduction) and Ill bet it resolves itself. I am not sure which yeast you used but if using the wyeast/ whitelabs used for this kit----> that specific strain does throw a small amount of IA. Nottingham is typically very low in IA so it would surprise me if you were using that yeast and got large IA production unless well over 70F during primary.
http://www.whitelabs.com/yeast/wlp051-c ... s=homebrew
Here is a link that shows you the actual VDK of the liquid yeast to give you example of types and amounts produced with the liquid yeast used on this kit. Look on the right hand side under the header “mini ferment data”.