New Biodegradable Fruit Wash Strips Pesticide Residue and Slows Spoilage

Shoppers who rinse fruit at home to remove pesticide residue and keep it fresh often treat those as two separate problems, but a new study from the University of British Columbia (UBC) suggests they can be tackled together. Researchers developed a biodegradable wash, made from starch nanoparticles, tannic acid and iron, that both removes surface pesticide residues and leaves a thin protective coating to help produce stay fresh longer. The team notes that about one quarter of fruits and vegetables are lost or wasted globally each year.

In the wash, starch nanoparticles provide a base, tannic acid, a plant compound found in many foods, adds chemistry that interacts with pesticide molecules on the fruit's surface, and iron helps connect the tannic acid into a fine network on the starch particles. During rinsing, this structure helps wash pesticide residues away. When fruit is immersed, the same mixture forms a very thin surface film that slows water loss.

On apple surfaces, the wash removed more than 85% of thiabendazole, a fungicide used on some produce after harvest, compared with 48% for tap water, 65% for baking soda and 61% for native starch alone. It also removed 93% of acetamiprid residues and 89% of imidacloprid from apple surfaces, though the researchers note the method only addresses residues on the surface, not pesticides that moved into the plant's tissue while it was growing.

The wash also slowed spoilage. Over 15 days, untreated grapes lost around 45% of their weight, while treated grapes lost only 21%. Fresh-cut apples lost 17% of their weight over 48 hours when untreated, compared with 9% when treated with the wash, and the coating also slowed oxidation and inhibited a test bacterium in laboratory experiments.

The researchers estimate the raw-material cost at less than $0.032 per apple and say a realistic near-term use would be in post-harvest processing plants rather than home kitchens, since facilities can control washing time, concentration and disposal more precisely. They are also developing a household spray formulation, though they say the wash still needs testing on more fruits and vegetables and must go through regulatory steps before real-world use.