Pasteurizing Fermented Cider with UV

I know that you are supposed to keep beer out of sunlight because it effects the oils in the hops that you extracted. But for the effort of pasteurizing cider in order to back sweeten it, would UV light be acceptable? I cant see any reason why not, but if there is let me know.

I am thinking of racking off from the fermenter into the keg and dropping one of these bad boys in over night:
http://www.amazon.com/dp/B005H486TG/?tag=skimlinks_replacement-20

According to this article, you're going to need to expose them for quite a while:
http://www.livestrong.com/article/252729-the-effects-of-uv-light-on-yeast/

MrFinstad said:

According to this article, you're going to need to expose them for quite a while:
http://www.livestrong.com/article/252729-the-effects-of-uv-light-on-yeast/

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"...while the University of St. Andrews study exposed the yeast to six hours of UV light, which killed 60 percent of the yeast cells."

I was planning on just leaving it in over-night. So this sounds like it should work. I was just wondering if there is any no-no about UV light on cider itself like there is beer.

COULD this be bad?

UV has the annoying property of being easily blocked by liquid. The penetration through probably won't be sufficient to kill the yeast off.

I would suppose that cider makers run it through a fairly narrow tube when it's exposed.

Watch out, this is not a linear phenomenon : if 6 hours kills 60% of the yeast, 12 hours won't kill 100%, but 60% + (40%*60%) = 84%.

But you should be able to get more then 60% attenuation in 6 hours ! Take a look at aquarium UV sterilizer on ebay. Even the cheapest 5watts are rated for 35 gal aquariums. Their goal is not however to completely sterilize an aquarium, but to keep the algae count very low. The moment you stop using them, algae come back and so will your yeast if you don't get 100% of them killed.

There must be some guidlines for using UV in food sterilization with 100% attenuation. Otherwise, you will want to run a residual activity test to find out just how much sterilization is needed : every 30 minutes of running the pump and uv, take a sample and incubate it in a sugar / water / nutrient solution at the ideal temperature and concentration for your yeast. Store them all in a warm spot and taste them 1-2 week later for traces of alcohol.

In all honesty, you've just saved yourself using metabisulfite. You might still want to use sorbate if you're planning on keeping the cider for a long time in warmish conditions. If there's a tiny amount of lively yeast in there, given enough time they will reproduce exponentially and convert your sugar. Sorbate will prevent their expansion.

UV for sterlization is tricky. You need a much higher output of UV, which means a big bulb and lots of $$

Also anything suspended in the water, or anything that clouds it will decrease the penetration by UV in an exponential manner

Basically what Im saying is that this isnt gonna work for bottle pasteurization of your cider

Cold crash it, and if you plan on bottling hit it with a bit of sorbate

I have worked extensively with UV sterilizers in water quality applications. Typically the bank of bulbs takes up an entire room (they're the size of 4ft. fluorescent bulbs and to get the kind of output you need to achieve sterilization you need lots of them). Water is trickled over the bulbs at low flow rates and very shallow depths (and that's for water that is already gin-clear). The aquarium sterilizer that you posted is designed to control algae populations by overloading their photosynthetic apparatus with UV light. This basically keeps the algae from being able to photosynthesize. They die as a result of not being able to produce the cellular products they need. The UV intensity of this piece of equipment is not sufficient to kill microbes (including yeast) outright. Like someone mentioned earlier, you would need a seriously badass setup to achieve what you have in mind. That equipment is not commercially available and it costs tens of thousands of $.

You want to protect cider from light! It won't skunk like beer, but will get "light struck" by UV light.

ajbram said:

I have worked extensively with UV sterilizers in water quality applications. Typically the bank of bulbs takes up an entire room (they're the size of 4ft. fluorescent bulbs and to get the kind of output you need to achieve sterilization you need lots of them). Water is trickled over the bulbs at low flow rates and very shallow depths (and that's for water that is already gin-clear). The aquarium sterilizer that you posted is designed to control algae populations by overloading their photosynthetic apparatus with UV light. This basically keeps the algae from being able to photosynthesize. They die as a result of not being able to produce the cellular products they need. The UV intensity of this piece of equipment is not sufficient to kill microbes (including yeast) outright. Like someone mentioned earlier. You would need a seriously badass setup to achieve what you have in mind. That equipment is not commercially available and it costs tens of thousands of $.

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Totally what I was going to say...

Yooper said:

You want to protect cider from light! It won't skunk like beer, but will get "light struck" by UV light.

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Light struck? What does that even mean?


Also,
I do not have the means to cold crash it and I am not bottling. I am kegging. So is the only other real option to put it in my boil pot and bring it up to 160 for a few minutes?

http://en.wikipedia.org/wiki/Wine_fault#Lightstrike
https://www.homebrewtalk.com/f32/cider-bottle-color-brown-v-green-v-clear-236066/

One of the standards for milk is 30 minutes at 145F. At 160F less than 30 seconds will do the trick.

Yooper said:

http://en.wikipedia.org/wiki/Wine_fault#Lightstrike
https://www.homebrewtalk.com/f32/cider-bottle-color-brown-v-green-v-clear-236066/

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I never worked with wines (dislike the taste) so I was totally unfamiliar with the term. Thanks!