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Is Yeast UV Light sensitive?

I know you have to be concerned with UV exposure of beer in general, but if I harvest and wash yeast for later use, does it need to be stored in a light-protected environment? I know a lot of people say they use mason jars; are they covering them?

I don’t think you need to worry about light bothering yeast. A couple reasons:

  • Yeast are naturally occurring in the air
  • White Labs sells yeast in clear containers

If that does not reassure you, you can take comfort in this: the inside of your refrigerator will be dark when the door is closed (unless off course it has a glass door).

[quote=“kcbeersnob”]I don’t think you need to worry about light bothering yeast. A couple reasons:

  • Yeast are naturally occurring in the air
  • White Labs sells yeast in clear containers

If that does not reassure you, you can take comfort in this: the inside of your refrigerator will be dark when the door is closed (unless off course it has a glass door).[/quote]

Very funny you bring this up! It is like you were at our breakfast table this morning… My wife said the same thing about the door being open and my 5 year old son convinced me to put a plate under the mason jar as he was concerned light would come up through the glass shelf and damage the yeast on the bottom. Beer paranoia has taken over our whole house!

I should have thought of the clear vials from White Lab. Good point.

The problem with light is with the hops in the beer. Washing the yeast should remove any hops so you shouldn’t have any problems.

Six weeks is a very long time for yeast to be active in a beer. You either have outgassing due to a low pressure system coming through or warming of the beer, or you have something other than yeast active in there. Or perhaps you had the beer much too cold during fermentation and the yeast are just waking up again.
Take a gravity reading to see if it has hit FG, and take a taste to see if the flavor is right.

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