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.
At room temperature the untreated strawberries stayed mold-free for just two days, compared to the four-day staying power of treated strawberries. Cut apple slices stayed fresh for roughly 24 hours while the untreated controls began to show visible signs of decay at about 12 hours. The treated grapes, meanwhile, lasted almost 14 days, taking a full week longer to show signs of wrinkling and shrinkage than the untreated fruit.
Overall, the novel agar dip extended fruits’ shelf life by at least twofold, and reduced weight loss at the four day mark from 30% to 13%. The researchers say the coating has antibacterial qualities which can explain its preserving features, is safe for human consumption, maintains the nutritional quality of the treated fruit, and can easily be washed off when food is ready to eat.
A lifecycle analysis also revealed that the coating had a lower or equivalent emissions impact to refrigeration. And although these reductions were relatively modest, the researchers say the benefits would become much more significant when extrapolated to a whole cold chain system, where small gains can add up to big savings.
In Canada where the research was based, food waste is a huge problem, with some reports estimating that 46% of fresh produce is lost or wasted in the country each year, valued at $58 billion.
Upgraded with commercially-available agar and used on a wider range of fruits, the researchers believe their invention could make a real dent in this problem, becoming a “practical, sustainable strategy to mitigate food loss and build resilient fresh produce supply chains,” they write.
Yang et. al. “Self-Assembled Metal−Phenolic−Agar Microparticle-Derived Coatings Enable Scalable and Sustainable Fresh Produce Preservation.” Agricultural and Food Chemistry. 2026.
Image: Slashio Photography for UnSplash
