1. You need really good surface contact to get the diffraction on, so you can only really apply it to flat, uncurved surfaces
2. You need to apply it while the chocolate is hardening. If you're using a mold, you cast the chocolate upside-down so only the base is exposed during setting. You can't diffract the part people will actually see.
3. The effect is really fragile. Chocolate melts at around body temperature, so if you hold the piece for too long, the diffraction disappears. I've been able to transport diffractive chocolate in a padded box but don't think I could wrap the chocolate directly.
I assume the transportation is the real problem. Even taking this sort of thing home from a store might lose the effect.
I can get a pretty decent temper on chocolate and I make bonbons once in a while, but I have still found that you can lose fine surface details with a temperature that is a comfortable "room temp" for humans.
It's something that would need to be created in a retail confectionary for immediate consumption. And, people might demand refunds when the slightest heat ruins it should they attempt to transport them without a cold chain.
There was a Swiss startup called Morphotonix that made holographic chocolates [1]. The company and its holographic-imprint tech are still around, but they've moved on to other markets. That suggests they just couldn't get prices low enough to make it appealing.
I feel weird about edible artwork. Do I buy it for food or do I buy it as a piece of art? How many of it would I ever buy? Then there's also the added costs to both sides. It might be very niche.
The parent comment means "plating" as in the art/activity of arranging food on a plate [1]. Not, I presume, the manufacturing process of coating something with a thin layer of metal.
In all seriousness though, this would be pretty cool and I'd love to try it. I suspect that some of the problem is just that companies tend to constantly push to deliver the bare minimum while charging the most. Holographic chocolate would take more money to make and companies are always trying to charge you as much as you're willing to spend for chocolate while giving you the lowest quality/effort product you'll still pay for. While I wouldn't expect to see something like this showing up in the candy aisles of your typical grocery store smaller fancier places will be willing to do
it and charge a premium
It isn't a matter of money, it's just too delicate to sell: unless you distribute bonbons or tablets still in their mold, to be cooled and extracted just before eating, even mild heat applies a lowpass filter to micrometer scale surface features instantly and unrecoverably.
