The last 2-3 batches I have made have both come out with a fruity banana flavor. They would have made wonderful heifewizen had I intended that way. All were intended to be American ale or pale ales. Both were relatively clear and I clean like crazy so I don't suspect contamination. Could it be a lack of oxygen for the yeast? Any suggestions would be great. I'm relatively new to this and trying to learn as much as I can. Also I would really like a beer to turn out like I intend it to.
Fruity banana taste/flavour is common in wheat beers. To be more spesific Weihenstephaner has it.
Several yeasts (wb-06 etc.) produce banana flavour taste in particular warmth condition.
My last wheat beer batch was fermented between 20-21 celcius and it has a little bit of it. It is more spicy and sour. Between 23-25 celcius though it should produce more banana like flavour.
If it smells/tastes right enough to drink i wouldnt say its contaminated. Just be carefull about the room temperature and keep it ideal for your yeast cells.
The temps you mention in the comments look about right, my guess would be you are under pitching. I have managed deliberately to get banana flavours with both S-04 and US-05 by bumping up the pitching and FV temp for the first 2-3 days of fermentation, but if you are holding it around 68F(20C) then you should be OK.
You could try:
- pitching at a slightly higher rate
- pitching a couple of degrees colder
- ensuring good aeration of the wort
I know you said you clean like crazy but...do you strip down you cold side ball valves. I take mine apart now after every brew and they go into PBW...every time. Ball valves don't stay clean, three piece ball valves can be stripped down and cleaned. I have one that is much better than the rest but it still ends up with some wort in it intermittently, my ball valves on the conical are always yeasty.