Can a lack of oxygen in wort generate an increase in fusel alcohols given that a fermentation is still healthy/vigorous?
Background for those who are interested
I have been struggling to determine the cause of strong fusel alcohol presence in my brews. My most recent beer that I brewed was done in my chest freezer at 17-18.5C ambient temp using Saf s-04 yeast. This is a 5% beer. Upon opening the pail after two weeks I noticed oil slicks on top and a medium fusel alcohol taste. I brewed 1.5 Gallons for a 2 gallon pail.
I don't shake or rock the wort before pitching. I just pour my wort at a high height into the pail. I then add a packet of dry yeast without creating a starter. This method has worked for me in the past, finishing off a vigorous fermentation in a week.