Many consumers buy fruits and vegetables, bring them home and wash them in the sink to remove pesticides and other contaminants from the outer skin before preparing and eating them. But new research suggests washing produce is probably not effective enough to remove pesticide residues.

The study was published in the journal Nano lettersexplained how researchers developed a form of surface-enhanced Raman spectroscopy (SERS), resulting in a high-tech imaging method that they then used to examine pesticide residues on produce. Although the research focused on the technology developed by the authors, concerns about pesticides and food safety were also raised due to the results the technology produced in experiments.

The researchers developed a flexible and nearly transparent membrane made from a cellulose hydrogel film that was stretched and wrinkled and then coated with a silver nitrate solution, the American Chemical Society explains. The result was a membrane that can use SERS, which can detect trace amounts of certain compounds, particularly for testing for pesticides.

After developing this membrane to detect pesticides, the researchers put their development to the test. To do this, they first sprayed two pesticides, thiram and carbendazim, on apples and then allowed the apples to dry.

After the apples were dried, the researchers followed the same procedure that consumers use after buying fruits and vegetables at the supermarket: they washed the apples. After washing, they placed the membrane over the whole, unpeeled apples and applied the SERS method. This revealed traces of the pesticides that had been applied to both the apple’s peel and the outer layer of the apple pulp.

“This suggests that the pesticides have penetrated into the pulp layer and that conventional fruit cleaning processes cannot completely remove the pesticides,” the authors write in the study.

However, when the researchers peeled the apple, they removed enough pulp that had detectable levels of pesticides. Therefore, the authors wrote, “…we believe that the peeling process can effectively avoid the hazards of pesticides in the epidermis and epidermal pulp, thereby reducing the likelihood of pesticide ingestion.”

The team’s new imaging method using SERS could also be used on other foods. In their research, the study authors found that their development could be useful in analyzing contaminants in foods such as chili powder, rice, cucumbers and even shrimp.

“This is actually helpful in understanding how these pesticides penetrate,” Michael Hansen, chief scientist at Consumer Reports, told The Guardian. “This is further scientific evidence that there is indeed a concern. Don’t just think that washing is going to help you.”

This article originally appeared on EcoWatch.com and was syndicated by MediaFeed.org.