Glover's team found that specially structured layers of cellulose reflect light off the berries' skin. Thicker layers of this cellulose reflect red and green while thinner layers shine blue. Unlike pigments, since the shine is produced by the structure of the cellulose it never fades as long as the cellulose structures remain intact. The researchers found that samples of the plant preserved in an herbarium since the 19th century still glistened like new.
"By taking inspiration from nature, it is possible to obtain smart multifunctional materials using sustainable routes with abundant and cheap materials like cellulose," lead author Silvia Vignolini, of the University of Cambridge, said in a press release. "As an example, edible cellulose-based nanostructures with structural color can be used as substitutes for toxic dyes and colorants in food. Moreover, the fact that the processes involved in cellulose extraction and manipulation are already used in the paper industry facilitates the use of such materials for industrial applications such as security labeling or cosmetics."