Researchers have developed a novel fresh produce wash that removes up to 93% of pesticides from the surface and doubles as a preservative, keeping fruit fresher for days longer than normal. What’s more, the wash is mostly made up of biodegradable starch.
Pesticides are often loaded onto fruit and veg and even with regulation, it can be hard to keep amounts in check. Data from Canadian food safety agencies found that the non-compliance rate for pesticide residues on food increased from 0.4% to over 2% in the four years between 2016 and 2020, the study reports.
The researchers’ inventive solution requires just three ingredients: starch, coated in tannic acid, a natural plant compound, and iron, forged together into nanoparticles, and suspended in a solution.
To test it out, they first applied three types of commonly-used pesticides to apples at real-world levels: thiabendazole, acetamiprid, and imidacloprid. Next, they analyzed how their nanoparticle-infused wash compared with water, the only available method most people have to clean their produce.
The differences were stark. While rinsing with water was able to remove about 50% of the pesticides attached to the apples’ surface, the nanowash eradicated almost double that, varying slightly depending on the pesticide type: the wash cleared 93.5% of the acetamiprid, 89.03% of the imidacloprid, and 86% of the thiabendazole.
The success comes down to a precise reaction that takes place between iron and tannic acid, which together create an absorptive effect that helps to sponge chemicals off the fruit’s surface.
The researchers went a step further, to explore whether their invention could help tackle another huge food system challenge: waste. They suspected that their wash could be used as a treatment to provide a preservative effect—and they were proved right. When they dipped two types of fruit, cut apples and fresh grapes, into a nanoparticle solution, they found that the cut apples took longer to turn brown than the untreated fruit. The grapes, meanwhile, maintained their shape for 15 days, compared to the untreated fruit which had grown noticeably wrinkled and shrunken by that point.
In both the treated apples and grapes the rate of weight loss was also halved compared to the untreated fruits, suggesting that they had been able to retain more moisture. Tests on the wash showed it had antioxidant and antimicrobial properties, which seem to provide a protective coating on the fruit and to slow its degradation.
The wash poses no health risks to consumers, and in fact the added sprinkling of iron may have a nutritional benefit, the scientists say. It will take a while for this innovation to reach consumers in their homes, but in the meantime the researchers have set their sights on industry, where they say their invention could be quickly scaled and used to clean produce before it reaches people’s homes.
“Our early cost estimates suggest it would add roughly three cents per apple—comparable to current commercial coatings, but with the added benefit of pesticide removal and extending shelf life,” the researchers say.
Yang et. al. “Dual-Function Metal−Phenolic Network-Capped Starch Nanoparticles for Postharvest Pesticide Removal and Produce Preservation.” ACS Nano. 2026.
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