Bottled up some beer the other day, and I live among graduate students so I put a call out for bottles and got what I needed, but two of them were corona clear bottles. Now, I used them and I'll store them in a dark place and will drink them in the first week, so I doubt I have real cause for concern of skunking. That said, I wanted to ask around the homebrew community to see if light skunking has ever been a problem for any of yall. Firstly, its been some years since my UC Davis brewing days, so I've forgotten a lot of the biochemistry involved. If I remember correctly, skunking is mostly due to the presence of iso-alpha acids or other hop compound (please correct me if I'm wrong). Are hoppier beers or dry hopped beers more susceptible to being skunked? Or is there another characteristic of a beer that makes it more/less susceptible? Secondly, how long after exposure do the off flavors appear and is it a function of how much light got in? What kind of light skunks beer (any, UV, sunlight, etc)? I know most of our bottled beers go into brown glass because we have been socialized against any other color, but anyone have anecdotes about their beer being skunked? Does this ever happen on a homebrew scale (not shipped, consumed super fresh, etc)? Cheers
All my beer is packaged in brown bottles and, when not in the fridge, they're kept in boxes or crates that get essentially no light. I don't remember any of my own homebrews getting skunky. You could do a personal test with the two Corona bottles, like condition one in the dark and another in light. This BYO article has some quick info on the Effect of Light on Beer (I don't think it's behind a paywall). One excerpt: "....the light wavelengths that cause beer to skunk fall between about 350 and 550 nanometers" That includes fluorescent and LED, but does not include incandescent or halogen.
It hasn't been a problem for me, but I've never used clear bottles. That's part of it. The pathway needs oxygen (present to some degree in all beer), riboflavin (vitamin B from the yeast, acts as a catalyst), isohumulone (isomerized AAs), proteins, and sunlight to kick it all off. It would be more accurate to say that beers with more iso-AA bitterness are more susceptible. Dry hopping provides AAs, but they are not isomerized. In strong sunlight, it can happen in minutes. Maybe even faster, but I'm not sure. Yeah, I'm 99% sure it's a function of how much UV gets in. Or put a different way, I'd be pretty surprised if UV were not typically the limiting factor. My understanding is that it has to be UV, either from sunlight or artificial. I've never heard of anyone having an accidental beer skunking problem from artificial UV. My guess is that it's because typical fluorescent bulbs don't emit much. But I have read about experiments with intentionally high artificial UV that did skunk beer. PeopIe have had homebrew skunked. You mention "on a homebrew scale." There's nothing in the chemistry to make homebrew any less susceptible to skunking. ETA: If I never read "on a homebrew scale" again in my life, I'd be okay with that. Every bad thing that can happen to large batch commercial beer can also happen to homebrew. In a (very) few cases, there are reasons why bad things are less likely to happen or less impactful if they do happen. </quasi-rant>
Skunking can happen with light in the blue to green wavelengths. I have had beers skunk very quickly in direct sunlight, 1 minute or lass. Someone pointed out on another forum that Vitamin B is not required, it is a catalyst in one of the pathways. Florescent light will skunk beer. Better beer stores have filter material on their bulbs. I don't pull the 6 pack from the front of the shelf. I had a beer skunk from the time it came from the keezer to the bottles for competition. Bright sunlight was coming through the window of the South facing garage door. I now block window off when packaging.
Hmmm. I don't doubt this, mainly because I've never known you to make statements of fact lightly. Do you happen to have a source for this? ETA: I just now google up a few pages that state something similar, but can't find anything very scholarly. This is something I think is probably technically true, but not significant practically. I say that because if the (alternate) reactions could proceed fast enough/often enough to be noticeable without it, we should hear about skunked worts, with all the full daylight boils people do. Personally, I haven't heard of one, so my guess is that the riboflavin reduces the energy cost more than a little bit.
For your consideration from the website beer sensory science (MS, BS, Food Science and Technology - Published, Journal of the American Society of Brewing Chemists): “Since about the 1960’s it’s been well established that the blue part of the visible light spectrum (~350-500nm) is the most efficient at generating lightstruck flavor…” https://beersensoryscience.wordpress.com/2011/03/17/lightstruck/ Cheers!
@VikeMan Boy this took a while to find, 2008. Some data. http://media.libsyn.com/media/basicbrewing/bbrskunking.pdf
I have all colors clear to brown. No problems at all since all bottles are stored in the celler where it is black and no light unless I turno N the lights to get some.
My use of the phrase was especially in reference to the smaller number of links in the supply chain. The reason I brought it up was because skunking in commercial beer or otherwise is likeliest to happen during changes of hands, like during shipping or coming home from the store. Thanks for the replies!
