Edible holograms could embellish food of the future
Image credit: Dreamstime
Researchers from Khalifa University of Science and Technology in the UAE have developed a laser-based method for printing holograms on films of dried corn syrup. The technique could one day be used to label products.
Holograms are photographic recordings of patterns of light, which use diffraction to reproduce the original 3D light field accurately. They are already incorporated into everyday items, from driver’s licenses to product packaging and bank notes.
According to an ACS Nano study, edible holograms could one day enhance foods. Hologram labels could be used to ensure food safety, indicate sugar content or add other information.
Most holograms are imprinted onto metal surfaces, such as aluminium, using lasers. In an effort to develop edible holograms, researchers have previously proposed creating holograms with nanoparticles, although these can generate reactive oxygen species which may be harmful to ingest. Edible holograms have been created on the surface of chocolates by pouring the molten chocolate into a mould etched with a pattern of miniscule structures which bend light at certain angles, although this requires a different mould for each design.
The Khalifa University researchers wanted to find a safe, fast and versatile means of applying holograms on food.
They created a solution of corn syrup, vanilla and water, then dried it into a thin film. They coated the film with a layer of non-toxic black dye and used direct laser interference to etch off most of the dye, leaving behind raised, nanoscale lines which formed a diffraction grating.
When light falls on these tiny structures, it is diffracted into a full rainbow pattern, with different colours appearing as the viewing angle varies. It is possible to control the intensity and range of colours by varying the space between lines in the grating, or by altering the sugar content of the corn syrup. Changing the amount of added sugar between 25 and 175mg increased the refractive index and decreased light absorption, influencing diffraction angle.
In order to prepare holographic food for the market – for controlling perception and beautifying the food – the researchers want to adapt the method to a food-grade dye to replace the non-toxic dye used in these experiments.
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