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To wrap up the end of my discussion on colors in the world of plant foods, we end with the rather weird subject of ultra-violet foods. There are several foods that are luminescent under ultraviolet light, and their behavior seems to have nothing to do with the other lessons of plant pigments. Foods that glow operate on their own rules. Maybe it’s not the most practical food discussion, but it sure does make an impression when you switch off the overhead lights and switch on a black light, and the appearance of everything changes. And who doesn’t find it a little thrilling to eat something that’s glowing? Or even to see something familiar that looks totally different, well, in a new light.
Before you start planning you black light cocktail party, a few notes about working with a black light: it isn’t a good idea to work too long with your food creations under a black light. I found that a minute or so was all I could manage before getting a magnificent headache. It doesn’t hurt to wear UV protecting sunglasses either.
The most dramatic example of a luminescent food is quinine. Quinine can be produced in a lab, but the quinine that ends up in our tonic water is from the bark of the cinchona tree. Quinine is used for medicinal as well as culinary uses. It is most famous for treating malaria, but it is also has anti-inflammatory properties and (though I claim no medical expertise) the internet tells me that more concentrated quinine has also been used to treat lupus and arthritis.
The flavor or quinine is distinctly bitter, and like most bitter foods some people love it and others just don’t get the appeal. Quinine is so bitter that tonic water is always sweetened, and even sweetened the flavor is bitter. The distinct flavor works well paired with sour flavors (lime and lemon are classics) or in low concentrations. The ultraviolet properties of quinine are quite remarkable. Turn on a black light with a bottle of tonic water around, and it’s like you’ve turned on a light bulb. I even had difficulty getting the exposure of the pictures, as the tonic water was so bright it threw off the exposure, literally outshining its neighbors.
Unfortunately, this potent luminous effect is easily thrown away if you add other opaque ingredients (a few experiments with mixing different plant materials with tonic resulted in unremarkable, murky drinks). If you make ice or jelly with tonic water, though, it will still retain it’s luminous properties. For a luminous cocktail, try making ice cubes out of tonic, and using plain soda water for the drink. Not only will the contrast look remarkable, but the flavor of the drink will slowly change as the ice melts.
When I read that green leaves glowed red in ultraviolet light I imagined bright red glowing leaves. The affect is far less dramatic. The color does look red, but it’s more like a red tint on black velvet. The bright green leaves turned dark, almost black with a slight reddish tint. And a strained puree of the leaves looked much the same. The real winner was green infused oils. Infused oils are a gorgeous bright green in day light, and in ultraviolet light they glow a brilliant orange-red. Oh, and they’re delicious.
To make an infused green oil, blanch a handful or two of aromatic greens (arugula, parsley, cilantro, mint) for a minute in boiling water. Plunge the wilted leaves into a large bowl of ice water. Pat leaves dry. Puree in the blender with just enough oil to make the mixture come together. Blend on high for at least a minute. Strain the oil through a fine meshed strainer. Use the oil to dress salads and cold dishes or provide a tasty and striking garnish.
My experience with bananas was similar to greens, I red that they glowed blue* in ultraviolet light and got excited. The result was, in my mind not that impressive. I might have been distracted by the phenomenally bright tonic water, but the slight bluish tinge was noticeable, but rather unremarkable. Now it might be the case that, like green leaves, the banana needs special preparation (blending, straining, infusing?) to bring this blue glow to a brilliant effect. But I just couldn’t get myself excited about the culinary uses of banana water or oil. So bananas are interesting to look at, maybe more so if you have bananas at different phases of ripeness. But I wouldn’t put them near anything very bright, or the (still noticeable) glowing will be easily overshadowed.
White foods easily reflect the glowing of an ultraviolet light and appear to glow. Milk, and other dairy and boiled eggs glow a brilliant purple. Thought they are more translucent, whitish fruits and vegetables will also glow, but not quite as brightly. The more opaque white the food, the more it will glow under UV light. The same is true for dishes. I was pleasantly surprised that my ceramic white plates did not glow too brightly. The glass coating on the glaze apparently filters some of the UV light, so not as much is reflected. White plastic dishes, however, bright white. If you’re trying to make the food be the star of the show, a dark colored serving dish would be ideal.
*More on bananas glowing blue when ripening, from the Telegraph.