I have been doing a little research, and most of the information I have been able to find agrees with everyone that quinine, which is in tonic water, is the brightest source for edibles that glows blue under uv lights. There do seem to be some alternatives though. This link leads to a recipe for edible glow paint, and is worth checking out. I could not find any information about what ratio of tonic water to other ingredients workes best, but it does not seem to take much. This recipe was the only one I found where the color of the glow and the color of the icing matched, with many other examples glowing an entirely different color than they were under regular light.
http://m.instructables.com/id/Glowing-Edible-Paint/There is conflicting opinions about whether translucent or opaque substances work best, as well as backgrounds. Plastic plates and cups, even clear ones, can glow brightly and outshine your creation, so test them out. Opaque foods seem to show up well on darker backgrounds, but translucent may look dimmer. The best examples I saw involved a glowing substance on a white or light colored surface if it was translucent, but it did not seem to matter if the glow was coming off an opaque substance. A nice dark background under that provided a good contrast.
For example, a glowing icing only on the lighter squares of a checkerboard cookie would be very distinct, as would the white on zebra stripes or white stars in a dark sky. If it is a light colored cookie, I would place it on a plate or background that does not glow, and keep in mind that glowing decorations on it won't appear as bright because the lighter cookie would not give as good contrast. Ideally for a translucent glowing gel you would have a dark plate, and maybe a dark or chocolate cookie, with a light/white surface (dough or fondant?) underneath the parts you want to glow. For glowing opaque icing, a dark cookie (or brownie, yum!) would work great.
Some people said they get a headache from working under a bright uv light for very long, and not to look directly at it. Wearing uv coated sunglasses might help or hinder the process, depending on who you ask. I would suggest you figure out what glows the best, then switch to normal light to assemble your cookie, only turning it back on to apply glowing decorations you can't see without it. And of course to admire your glowing masterpiece.
Before I forget, I apologize to anyone who thinks I should have credited them for this information, but a great many of these ideas were used in so many sources that I have no clue who should have credit. It is kind of like trying to provide a source for the first person to dunk their cookie in milk. I do not have a uv light, so I cannot confirm this information, but I checked many sources to compile it, including asking friends and neighbors. I have also added a few ideas and guesses about what might work well, but you need to test them out first.
Mountain dew and some energy drinks contain guanine, taurine, and/or B-12, which makes them glow yellow or green, but I don't know specifically which ones. They could be used to replace liquids in some circumstances. This link explains a bit, and also says that not all uv lights glow in the same wavelength, so choose a light carefully. (A friend told me not to get a round bulb, but a bright light with a long narrow tube shape such as some fluorescents.)
https://canadianmuseumofnature...e-dark-glowing-food/This link includes a recipe for buttercream icing with uv-glow, but is basically just icing with tonic water added for the quinine. It seems like royal icing would work with this too, but if it does not glow enough you might want try it using meringue powder mixed with tonic water instead of some fresh egg whites, to add a higher amount of quinine.
http://www.ehow.com/list_72220...low-black-light.htmlThis link explains how to make uv-glow (not glow-in-dark as the title implies) piping gel with tonic water from scratch, or add tonic water and gelatin to pre-made. I think this is a very viable idea, as is making "jigglers" with plain gelatin, tonic water, and sugar with little or no coloring added.
http://www.ehow.com/how_593916...dark-piping-gel.htmlThis link is one of several sites that says bananas glow a dim blue under uv light, and that the glow intensifies somewhat as they ripen, and hit the brightest just before they start to turn brown, then go very dim. The peels of apples and pears are said to do the same thing, but I don't have specifics and would certainly use well washed organic.
http://www.ehow.com/list_71669...der-blacklights.htmlI have seen suggestions of many white foods that glow purple, such as marshmallows, coconut, milk, and vanilla ice cream, but I am not certian if the dairy glows, or just shows up really well. Sugar and salt on the rims of cocktails are said to glow, which made me wonder about sanding sugar. You might want to try holding your white food coloring as well as un-whitened icing under a uv light to see which, if either, glows more. If the white (or neon or any light) gel coloring glows, it would be great painted on a dark iced background, as some people have done for a chalkboard look.
Supposidly fried egg whites glow blue, hard boiled eggs glow yellow (or maybe blue), and egg shells glow lavender-pink. Wonder what color meringue is if it glows? Worth trying out. Maybe a thin layer of sweetened cooked egg white could be cut out with a fondant cutter and be placed on cookies when serving?
As an aside, I remember as a kid hiding in the dark under a blanket to eat lifesavers, because the friction caused little sparks of "lightning" in my mouth when I chewed. (Sorry, don't remember what flavor) A couple of sites I visited say wintergreen lifesavers (and maybe Velamints?) glow in uv light. This might actually be the best way to get a good taste, and you have the security of knowing it is definitely edible.
There have been suggestions for making hard candy or candy canes with tonic water, and I wonder if letting the water evaporate, leaving behind just the quinine, would give you a substance to mix with edibles that don't have water in them? I am not a candy maker myself, but the suggestion to make white chocolate candy with tonic water has left me baffled, as I thought water made chocolate seize. Somewhat unrelated, ice made from tonic water glows very bright, but melts faster, so dilute with plain water to avoid bitterness for drinks.
Apparently chlorophyll glows in a bright red color, but is hard to see against a green background. Mixing blanched (and dried off) spinach or fresh mint leaves in a food processor with olive oil (which glows a dim yellow), then straining it through cheesecloth to remove the greens makes a red/pink glowing drizzle. Rumor says using alcohol instead can make somethin akin to a chlorophyll extract. Maybe pesto glows orange in uv light?
Citrus juices are often used in uv-glow cocktails, and I suspect it's because the taste may hide the bitterness of the quinine, but remain semi-translucent. Hiding the bitterness of quinine was a major theme, and sugar with lemon, lime, or pineapple a popular solution. My suggestion would be to see if you can get a good glow with small amounts of tonic water. If not, make concentrated decorations (royal icing transfers?) and use them sparingly, perhaps on fondant or something else that could be easily removed.
An allergic reaction to quinine is supposedly about as common as reactions to any other common foods, such as peanut butter. However, some people seem concerned that since tonic water is usually used in cocktails, and children don't typically consume it, they may first discover the allergy when trying uv-glow treats. You will need to do your own research to decide if this is a concern for you.
Good luck, and please share with if any of these work well. I am excited to try them too at some point.
