A thin, edible coating made partly from seaweed helped strawberries stay firm and mold-free longer in laboratory tests, offering a possible new way to reduce produce spoilage and food waste.
The coating also helped grapes and sliced apples retain quality, but the findings do not show that it can replace refrigeration or that coated produce is ready for grocery store shelves. Researchers still need to test its taste, safety, cost and performance under real-world storage and transportation conditions.
The study was published in the Journal of Agricultural and Food Chemistry.
Researchers at the University of British Columbia developed the coating using agar, a substance derived from red seaweed that is commonly used as a food thickener and vegan alternative to gelatin.
They combined the agar with zinc and tannic acid, a plant compound found in foods such as grapes and tea. Together, the ingredients formed tiny particles that created a clear protective layer when fruit was dipped into the solution.
“We wanted to find a simple alternative to cold storage,” said senior author Tianxi Yang, an assistant professor in UBC’s faculty of land and food systems. “Once we added the coating, the fruit became far less sensitive to changes in temperature and moisture and stayed fresh longer.”
Strawberries spoil quickly in part because they lose moisture and are vulnerable to mold and bacteria. Refrigeration slows that process, but maintaining cold temperatures during shipping, storage and retail requires energy and specialized equipment.
In the experiment, coated strawberries stored at room temperature lost less than half as much water over four days as uncoated strawberries. They also remained firmer and retained more vitamin C and antioxidant compounds.
Uncoated strawberries stored at room temperature began developing mold within two days, according to the researchers. Coated strawberries remained mold-free for at least four days at room temperature.
The release describes the coated berries as staying fresher than refrigerated strawberries, but that comparison requires context. Researchers compared coated fruit at room temperature with uncoated fruit kept in the refrigerator.
That does not show that the coating works better than refrigeration under identical conditions or that cold storage is unnecessary. Refrigerated strawberries that also received the coating stayed fresh for at least six days, suggesting that refrigeration continued to offer an additional benefit.
The researchers also tested the coating on grapes and apple slices. Grapes showed quality improvements for as long as 14 days, while the coating helped apple slices for about 24 hours.
The results suggest the technology could eventually help slow moisture loss and visible spoilage across several types of produce, but each fruit or vegetable would likely require separate testing.
The coating showed antibacterial effects in laboratory experiments and did not appear toxic when tested on human intestinal cells. Those results are early safety checks, not proof that repeated consumption is safe for people.
The study did not involve participants eating the coated produce, and it did not examine possible effects over longer periods. Regulatory review and additional food safety testing would be required before commercial use.
Consumers would also need to know whether the coating affects taste, smell, texture or appearance. The researchers reported that it dried clear, but the study did not include formal taste testing or measure whether shoppers would accept coated produce.
For people who would prefer to remove it, the researchers found that most of the coating could be washed away with tap water within two minutes.
The team also created a version using commercially available food-grade agar rather than laboratory-grade material. That version produced similar results in strawberries, an encouraging sign that the coating may not require a rare or highly specialized form of agar.
“It was exciting to watch the particles self-assemble in real time, from a cloudy, milky liquid into this incredibly uniform, protective layer,” said lead author Ivy Chiu, a doctoral student at UBC. “To our knowledge, no one had made an agar-based microparticle coating like this before.”
The researchers estimated that using the coating could produce a 14% smaller carbon footprint than conventional refrigeration and reduce freshwater ecotoxicity by about 85%.
Those figures came from a life-cycle assessment rather than a full commercial system. Environmental estimates can change depending on how the coating is manufactured, transported and applied, as well as the energy source used for refrigeration.
The analysis also does not establish that refrigeration could be eliminated throughout the food supply chain. Temperature control serves purposes beyond slowing visible spoilage, including managing food safety risks during storage and transportation.
Visible freshness is not always the same as microbiological safety. Produce may look firm and mold-free while still carrying microorganisms that could cause illness. The coating should not be interpreted as allowing consumers to ignore established storage guidance.
The most likely early use may be as an additional layer of protection rather than a complete substitute for refrigeration. If the technology works at commercial scale, it could potentially help produce tolerate short temperature changes, remain marketable longer or reach areas where refrigeration is limited.
“Our hope is to help keep produce fresh for longer throughout the food system,” Yang said. “If we can reduce spoilage during storage and transportation, we can reduce food waste while using less energy to preserve food.”
The researchers are now testing the coating on other fruits and vegetables and examining how it might be produced and applied at a larger scale.
Further studies will need to determine whether the coating continues to work during packing, shipping, grocery display and household storage. Researchers will also need to evaluate cost, regulatory requirements, consumer acceptance and protection against specific foodborne pathogens.
The study was supported by University of British Columbia Faculty of Land and Food Systems startup funds, the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation John R. Evans Leaders Fund and the British Columbia Knowledge Development Fund.