In a recent study at the University of Massachusetts, scientists showed that surface pesticide residues present in fruit and vegetables were most effectively removed by sodium bicarbonate solution when compared to either tap-water or a type of bleach like Clorox bleach.
Baking soda removes up to 96% of pesticides from fruit and vegetables. When mixed with water and gently rubbed on apple skins, the solution eliminates nearly all the reside left by two commonly-applied pesticides within 15 minutes.
The researchers applied the common pesticides thiabendazole - which has been shown to penetrate apple skin - and phosmet to organic red apples. These pesticides were left on the fruit for one day. The researchers then washed the apples with either tap water, a bleach solution or 1% baking soda mixed with water.
Electronic mapping technology was used to assess pesticide presence on the surface of, and inside, the apples. Results reveal that sodium bicarbonate mixed with water is the most effective way of removing pesticides from apples.
After 12 minutes of gentle scrubbing, the solution removes 80% of thiabendazole, while it takes 15 minutes to remove 95.6% of phosmet. Thiabendazole is thought to be more difficult to remove due to it more readily penetrating fruit's surfaces.
Peeling apples helps to remove pesticides that have penetrated the fruit, however, this will also reduce its nutritional content, according to the researchers.
"Removal of pesticide residues from fresh produce is important to reduce pesticide exposure to humans. This study investigated the effectiveness of commercial and homemade washing agents in the removal of surface and internalized pesticide residues from apples. Surface-enhanced Raman scattering (SERS) mapping and liquid chromatography-tandem mass spectrometry (LC−MS/MS) methods were used to determine the effectiveness of different washing agents in removing pesticide residues. Surface pesticide residues were most effectively removed by sodium bicarbonate (baking soda, NaHCO3) solution when compared to either tap water or Clorox bleach. Using a 10 mg/mL NaHCO3 washing solution, it took 12 and 15 min to completely remove thiabendazole or phosmet surface residues, respectively, following a 24 h exposure to these pesticides, which were applied at a concentration of 125 ng/cm . LC−MS/MS results showed, however, that 20% of applied thiabendazole and 4.4% of applied phosmet had penetrated into the apples following the 24 h exposure. Thiabendazole, a systemic pesticide, penetrated 4-fold deeper into the apple peel than did phosmet, a non-systemic pesticide, which led to more thiabendazole residues inside the apples, which could not be washed away using the NaHCO3 washing solution. This study gives us the information that the standard postharvest washing method using Clorox bleach solution for 2 min is not an effective means to remove pesticide residues on the surface of apples completely. The NaHCO3 method is more effective in removing surface pesticide residues on apples. In the presence of NaHCO3, thiabendazole and phosmet can degrade, which assists the physical removal force of washing. However, the NaHCO3 method was not completely effective in removing residues that have penetrated into the apple peel. The overall effectiveness of the method to remove all pesticide residues diminished as pesticides penetrated deeper into the fruit. In practical application, washing apples with NaHCO3 solution can reduce pesticides mostly from the surface. Peeling is more effective to remove the penetrated pesticides; however, bioactive compounds in the peels will become lost too."