If you notice a white powdery residue on plastic utensils, the culprit probably is one of two possibilities. If the utensils are brand new, the residue may be some substance left over from the manufacturing process. If you've been washing the plastic utensils, the residue likely is a result of minerals in your water reacting with soaps and detergents. Regardless of which scenario caused your residue, you can remove this powdery film using a simple cleaning technique.
Wash your plastic utensils in warm, soapy water as usual in order to remove any debris besides the white powdery film.
Soak the utensils in undiluted white vinegar for about 30 minutes. The vinegar works to clean, disinfect and dissolve any possible lime scale, which is the result of hard water and soap.
Rinse the plastic utensils and dry them before storing them.