Can a lack of oxygen in wort lead to increased fusel alcohol?

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.

Topic oxygenation fermentation homebrew

Category Mac

1
answered at

Hot, fusel alcohol flavors generally correlate to stress in the yeast — insufficient population, not enough nutrients, or insufficient oxygen levels in your starting wort. If you're getting these off flavors for even a smaller beer at 1.050, in the very least do the following:

  • in your boil, add yeast nutrients in the last 15 minutes of the boil, and

  • before pitching the yeast in your cooled wort (between 18-21ºC for ales, around 7ºC for lagers) aggressively swirl/rock your carboy for a few minutes. You want to swirl it aggressively enough so that you see swaths of small bubbles churning and mixing with your wort. A representative from Wyeast has recommended shaking for about a minute.

I don't brew very often with dry yeast, but you can dry pitch, and for the most part do OK. However, if you're taking the above two steps already, then you should look into making starters. Starters ensure that you've got a healthy, viable population of yeast sufficient to consume the long-chain sugars in your wort. If you've got a healthy culture and population of yeast and produce an environment rich in oxygen and nutrients, then you're a lot less likely to get the fusel alcohol biproducts in your fermentation.

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