A self-assembling coating made from seaweed and zinc can keep fruit fresher and lasting longer than even the cool interior of a fridge. This invention, described in a new paper from a team of Canadian scientists, enabled even delicate strawberries to survive at room temperature for four days without molding. It strikes two sustainability targets at once: reducing food waste, and limiting dependence on carbon-intensive cold chains.

The main seaweed ingredient in this invention sounds unusual but is actually a widely-used food additive and vegan gelatin-substitute called agar that is produced from red algae. This made up the bulk of the new fruit coating, but when combined with the micronutrient zinc and tannic acid it did something interesting that the researchers are still trying to understand, swiftly self-organizing into a thin layer of microparticles that evenly coated any fruit dipped into it. For this, the researchers tested out fresh strawberries, apple slices, and whole grapes.

Next, they trialled their new coating both inside and outside a fridge, comparing dipped fruit with fruit that remained untreated. This led to the most striking discovery, that coated strawberries at room temperature outperformed uncoated strawberries placed in the fridge. The treated, uncooled fruit held out for at least four days or more before becoming moldy, while the untreated but refrigerated fruits started molding on day four. Meanwhile, coated strawberries that were kept in the fridge were even more robust, lasting a full six days.