Think washing fruits and veggies makes them safe? Washing them under water may remove the dirt on the outer layer but researchers now suggest you might need to take an extra step and peel them to effectively remove pesticides.

A recent study published in the American Chemical Society's journal Nano Letters found that pesticides can penetrate beyond the peel into the pulp layer of the fruits. Therefore, simply washing produce may not be enough to avoid pesticide ingestion; peeling is necessary to reduce risk.

"This study, situated within the expansive realm of food safety, endeavors to furnish health guidance to consumers. Rather than fostering undue apprehension, the research posits that peeling can effectively eliminate nearly all pesticide residues, contrasted with the frequently recommended practice of washing," said Dongdong Ye, an author of the paper.

After investigating how pesticides affected apples using a newly developed surface-enhanced Raman spectroscopy (SERS), the researchers noted that "traditional fruit-cleaning operations cannot wholly remove pesticides." However, since during peeling more than 30 μm of pulp layer is lost as confirmed by ultradepth of-field microscopy, "the peeling operation can effectively avoid the hazards of pesticides in the fruit's epidermis and near-epidermal pulp, thereby reducing the probability of ingesting pesticides."

SERS is a sensitive, non-destructive imaging technique that can detect very low concentrations of substances with less energy than traditional Raman spectroscopy. It could be used in analyzing chemical mixtures, identifying harmful substances, checking the quality of products like pharmaceuticals and food, and monitoring chemical processes in production. The researchers believe that SERS could also be used to analyze contaminants in other food items such as chili powder, rice, cucumbers and shrimp.

The researchers developed a flexible and nearly transparent membrane NWCM-Ag, made from a cellulose hydrogel film that could use SERS. For testing, the team sprayed apples with two pesticides, thiram, and carbendazim, and let them dry before washing them under water as consumers would do. Using the new membrane and SERS method, they detected trace amounts of pesticides on both the apple's skin and the outer layer of pulp.

"This is actually useful for understanding how these pesticides move in. This is more science showing that, yes, there are concerns. Don't just think that washing is going to help you," Michael Hansen, a senior scientist at Consumer Reports told the Guardian.

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