First, we purchased pesticide detection cards that can identify commonly used pesticides. (The cards detect pesticides that fall into two general types based on their chemistry: carbamates and organophosphates.) Each card contains a white disk and a pink disk. The white disk is pressed onto the test area; after giving the chemicals in it time to react, the pink disk is pressed against the white disk so that a second reaction can occur. The presence of pesticide residue is indicated by the degree to which the disk changes from white to blue. If the disk stays white, this indicates a high concentration of pesticide residue. But if the disk turns blue, this indicates very little to no residue.

For our experiment, we chose grapes, which (like apples) are among the “dirty dozen” fruits and vegetables most likely to have pesticide residue even after washing. First we used the cards to confirm that there were indeed pesticides on the surface of the grapes. We then submerged some of the grapes in the baking soda solution and set a timer for 15 minutes. While we waited, we tried other cleaning methods with the remaining grapes: swirling them in the solution for just 30 seconds, rinsing them under cold running water, and soaking them in a vinegar solution. 

After each treatment, we rinsed the grapes in water, dried them, and applied the test cards. Soaking and swirling in the baking soda solution were the only two methods that turned the cards blue, indicating that both were effective at removing pesticides. That’s because carbamate and organophosphate pesticides tend to break down in alkaline solutions. 

One thing to keep in mind: The baking soda solution will remove only certain classes of pesticides. Spray pesticides that are designed to be absorbed cannot be rinsed away; neither can those that are applied to a plant’s roots.

Exposing fruit or vegetables to a baking soda solution is not a silver bullet for removing all pesticides. But it still removes some common types, and because the method is fast and easy, we’re still inclined to use it. Here’s how:

Swirl produce in a solution of 2 teaspoons baking soda per 1 quart water for 30 seconds (the produce should be submerged in at least 1 inch of water), and then rinse under cold running water.