Many grocery shoppers know the routine: bring fruit and vegetables home, rinse them, dry them and hope they stay fresh long enough to be eaten. But fresh produce is delicate. Grapes shrivel, apple slices brown and berries can spoil quickly.

At the same time, many people worry about what may remain on the surface of fruit they buy, including pesticide residues.

Cleaning and freshness are usually treated as separate problems that require different treatments. Washing feels like a simple act of control. But it’s not quite that simple.

The U.S. Food and Drug Administration recommends rinsing produce under running water and says soap, detergent and commercial produce washes are not recommended. Water helps, but it does not solve every problem.

Our new study suggests those goals may be combined. We developed a dual-function biodegradable wash that is able to remove surface pesticide residues and form a thin protective layer to help fruit stay fresh for longer.

The timing matters. Around one quarter of fruits and vegetables are lost or wasted globally each year. For fresh produce, even small gains after harvest can matter because quality can change quickly during shipping, storage and daily use at home.

What’s inside and how does it works?

The wash developed in the study is made from starch nanoparticles, tannic acid and iron. Starch is a plant-based material often used in food science because it can form films. Tannic acid is a plant compound found in many foods and plants. Iron helps connect tannic acid into a fine network on the surface of the starch particles.

In plain terms, starch provides the base, tannic acid adds useful plant chemistry and iron helps hold the structure together. During rinsing, this structure can interact with some pesticide molecules on the fruit’s surface and helps wash them away.

When immersed, the same wash can form a very thin coating layer. This is not meant to be a heavy wax-like layer. It is closer to a light surface film that can slow water loss and help maintain appearance. That matters because people often decide whether to eat or throw away fruit based on how it looks and feels.

Removing surface pesticide residues

The cleaning results were strong. On apple surfaces, the wash removed more than 85 per cent of thiabendazole, compared with 48 per cent for tap water, 65 per cent for baking soda and 61 per cent for native starch.

Thiabendazole is a fungicide used on some fresh produce post-harvest. We also tested two other pesticides. The wash removed 93 per cent of the acetamiprid residues and 89 per cent of imidacloprid from apple surfaces. These results suggest the wash can work across more than one type of pesticide residue, rather than only one special chosen compound.

There is, however, an important limit. The study focused on residues on the fruit surface. Some pesticides can move into plant tissue while the fruit is growing, which makes them much harder to remove after harvest.

A better wash should not be understood as a way to erase all pesticide exposure. It’s a tool for reducing what’s on the surface of a fruit or vegetable.

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Read more: Our study analysed pesticide use and residues across Europe. Here’s what we found

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Keeping produce fresh longer

The second part of our study looked at freshness. Over 15 days, untreated grapes lost around 45 per cent of their weight, while grapes treated with our wash system lost only 21 per cent. Fresh-cut apples also lost less weight over 48 hours, dropping from 17 per cent in untreated samples to nine per cent.

Those changes can impact what people buy. Treated grapes looked fresher after storage, and apple slices stayed lighter for longer. That kind of change matters outside the lab because produce that looks dried out or browned is less likely to be eaten.

The coating also showed an ability to slow oxidation and inhibited a test bacterium in laboratory experiments. This doesn’t mean the wash has completed all the safety tests needed for consumer use. However, it does suggest the coating may do more than simply sit on the surface.

What this could mean in practice

For now, a realistic use for our wash would likely be in post-harvest processing plants, not kitchen sinks. Processing facilities can control washing time, concentration, water handling and disposal more carefully than households can. We estimated the raw-material cost is less than US$0.032 per apple. Meanwhile, we are actively working on developing a household spray formulation for consumer use.

More work is needed. The wash should be tested on more fruits and vegetables, under commercial conditions and through the regulatory steps required before real-world use.

Still, the idea is useful because it reframes the problem. A fruit wash doesn’t have to be only a rinse. It could clean more effectively and then keep working, helping produce stay fresh, appealing and more likely to be eaten.

The research discussed in this article received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC).

Ling Guo and Tzu-Cheng (Ivy) Chiu do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.