Engineers have learned to apply a microscopic pattern to the surface of the chocolate, which reflects and refracts light, creating an iridescent color.
Traditional methods of coloring chocolate need special and precise changes in the formulation, the addition of pigments and coloring substances. However, the chocolate shimmering with all the colors of the rainbow, obtained by Anita Zing and her colleagues, uses a completely different effect and does not require any new additives. This is described in a press release from the Swiss Higher Technical School in Zurich.
The necessary shades arise due to the peculiarities of the microscopic structure of the material, which creates the effect of irisation. Such a “structural” color is determined not by the presence of pigments that absorb light of certain wavelengths and reflect others, but by refraction and interference of rays by the surface of the object. It is quite common in nature and gives color, for example, to feathers of birds, shells of beetles, or the inner surface of shells.
The developers say that initially, they tried to achieve the desired effect by coating the chocolate with a thin coloring layer of non-toxic materials – gold or titanium oxide. So they managed to get, depending on the thickness and other properties of the coating, a whole set of unusual colors: from golden yellow to dark blue. However, in the end, this approach was found to be too complicated, expensive, and economically inexpedient, so scientists turned to structural coloring.
By varying some stages of the preparation of chocolate, the authors were able to achieve the desired effect by applying a microscopic pattern to the surface, which reflects and refracts light in a special way. Interfering with each other, these waves gave it iridescent shades – without any additives, changes in the taste and texture of the product.
It is reported that the technology is easily scalable for real production. Scientists have already filed a patent application and are negotiating with several companies ready to arrange the production of a new chocolate, now – rainbow.