Chemical and Bio-engineering student Britt Michelsen writes in about her Kryptonite candy, which uses vitamin B2 to make this homemade confection glow.
For some time now, I’ve been playing around with Fluorescein, which is a dark red powder soluble in water and alcohol. It is commonly used as a fluorescent tracer. Though it is used e.g. in eye drops and biochemical research, it can cause adverse reactions (like nausea or vomiting). Because of this, even though only very small amount are needed I don’t think it is safe enough for candy (and it is not easy to get).
Sadly most phosphorescent substances aren’t classified as “food grade” (even though they are not toxic). In most “glow under a black light” food Quinine is being used, which is in Tonic Water (in very small quantities). In my opinion for candy it is not suitable thought, because of two major reasons: 1. the bitter taste and more importantly 2. it’s melting point is very close to the temperature you will need to make the candy.
So I had to find an other easy to get food grade chemical with a high melting point. My solution: Riboflavin, better known as vitamin B2 or additive E101. It can be found in most vitamin pills, is not toxic and fluorescents yellow under UV light (and even under direct light). The only set back is, that it is destroyed by exposure to light, but in our case it should matter because the process is pretty slow. Tthat is the reason why you should buy your milk rather in opaque containers and not in glass bottles.