Glowing Foods! Cooking Colorfully in Ultraviolet Light.

Introduction: Glowing Foods! Cooking Colorfully in Ultraviolet Light.

About: Enthusiastic cook, blogger and (sometimes) crafter.

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.

Quinine : 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.In a small percentage of people, quinine can cause an allergic reaction. Drinking tonic water is no more inherently risky than eating other foods with allergens like nuts, meat, fish, eggs, wheat-- you get the picture. Because it is an unusual ingredient, and many people have not heard of quinine allergy, an allergen-awareness note seemed justified.

The flavor or quinine is distinctly bitter, and like most bitter foods some people love it while 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.

Chlorophyll: 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. The red in these oils turns out so well, you can almost use the oil as a paint for your foods. The red shows up best on light colored foods or on a white plate.

Bananas: My experience with bananas was similar to greens, I read 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) glow on the peel and in the banana will be easily overshadowed.

White-colored foods: 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.

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    11 years ago on Introduction

    After doing some basic research into bananas (for the uber-scientific reason that they'd taste better than quinine) I found the following things that somebody could run with.

    It turns out that just before a section of banana skin turns brown it glows bright blue.

    Apparently the glowing of bananas (and probably the other green leaves you found) is due to the chlorophyll breaking down.  This could account for why your blanching process helped the glowing.

    A little deeper article on the phenomenon:

    According to the article this same breakdown in chlorophyll is what produces the color changes in fall leaves.  The difference is that the color these things change is a shade of ultraviolet instead of red or orange.

    Aside, I wonder if some of those trees that don't really change color in the fall (you know, the ones where the leaves get crusty, but stay mostly green) are actually just changing to a color invisible to us?  Kids, that could be a cool science fair project!


    Reply 11 years ago on Introduction

    Thanks for your thoughtful reply-- lots of great stuff to think about!

    re: bananas. The chlorophyll breakdown in bananas creates a different compound (fluorescent chlorophyll catabolites, which glow blue) than regular old chorophyll (which glows red). My understanding is that this chlorophyll breakdown is thought to be unique to bananas, and was undiscovered until a few years ago. I find it rather exciting that bananas are secretly turning blue just when they are ripe (though visible only to other critters with vision that dips into the ultraviolet spectrum). Just like raspberries or apples, but UV.

    As to the blanching process, the blanching helps to break down the cell walls, which aids the dissolving of chlorophyll into the oil. The cold water shock is there specifically to halt cooking (and chlorophyll damage), so I doubt it is a breakdown in chlorophyll that is causing the brighter glow. My best guess is that removing the extra plant fibers allows the florescent effect to appear more dramatically. (Though it is still a mystery to me why greens pureed in oil glow, but not those in water).



    Reply 10 years ago on Introduction

    The structure of chlorophyll makes it dissolve easyli in oil, but not in water. If you use water instead of oil, most of the chlorophyll is not dissolved and still captured in what is left of the cells.


    I posted this on another forum about glowing gin and tonic jelly, but I thought it would be useful to mention it here as well. Quinine is reasonably safe for most people to ingest, but it can also cause various allergic reactions. With the recent popularity of these glowing foods instructables, I think it is worth mentioning that too much of this substance ingested at one time can lead to serious health risks. That does not mean it is dangerous to prepare this food (as the required amount is generally so low), and I am not trying to scare anyone away, but people who are considering using quinine as a food ingredient should probably do a bit of research on its side effects. My concern is that eventually someone will want to have an entire glowing banquet from all of the different quinine instructables without being aware of potential risks. Enjoy your glowing food, but be careful.


    Reply 11 years ago on Introduction

    You're quite right to note that quinine is an allergen, (adding footnotes to my posts now) and can be dangerous to folks with that particular allergy. But the risk of drinking tonic water is no more than eating other dishes which contain allergens like soy, meat, nuts, fish, wheat and eggs.

    Normally I wouldn't add footnotes when writing a recipe with allergens, for the reasons that 1. there are way too many allergens and nearly every recipe would come with a disclaimer and 2. the amount of people with that specific allergy might be a very tiny percentage of the population, most of whom know that they are allergic. Because quinine is an ingredient that many people are not familiar with, I think adding a footnote is reasonable.

    With regard to the side affects of quinine-- when used as a drug, quinine does have serious side effects. But the level of quinine in tonic water is a tiny fraction of what is in a therapeutic dose. So the risk of side affects associated with culinary uses of tonic water is almost impossibly low.

    Thanks for your input. Cheers.