Very little information can be found around internet about "photoisomerization" in beers. This is a chemical reaction on acids of hops if exposed to the light, such as in transparent bottles.
I could find that the visible light of blue frequency only, and the invisible light UV (only), can cause photoisomerization, but it isn't widely known neither are consensus about that.
Someone could confirm that ? Or give more detailed information about the light frequencies that can cause photoisomerization ?
Assuming that just UV + blue light can cause it, I have a lot of questions like:
- Why UV and blue light filters aren't used to non-brown bottles keeping the beer protected against the photoisomerization ? Just costs ?
- What are in brown bottles that can filter UV ? What is their efficiency to filter UV and blue light ?