There are a variety of commercial vegetable and fruit washes available in the market these days and many claim they clear the veggies and fruits of bacteria, viruses and pesticide residues. The question is do they?
Washing fruits and vegetables before eating them is of course, inevitable – this applies to all fresh produce – organically or inorganically grown – given there could be soil, dust and handling related contaminants that a good wash could clear off. Chemicals used in crop production are a little complicated though and one needs a little understanding of how they actually work to appreciate where their residues lie.
Pesticides applied to crops fall into a few categories:
These are applied to soil and are absorbed by plant roots before being translocated through the plant vascular system for the chemicals to act. Typical examples are insecticide granules such as carbofuran that are applied to the soil but control a lot of insects that affect the plants. Most fertilizers also fall into the soil application category.
These are sprayed directly on the plants drenching the leaves and stems. Some of these are absorbed by the plant and moved into the plant vascular system while others stay and act on the plant surface. The type of pest determines which type of pesticide needs applied – for example, sucking insects such as aphids need an insecticide that enters the plant system while leaf eating caterpillars typically get sprayed with an insecticide that stays on the plant surface.
In summary, there are chemicals that enter into the plant vascular system (systemic pesticides) and those that stay on plant surface (contact pesticides). It is now simple to deduce that no amount of washing the vegetables and fruits will reduce any systemic pesticide residue, because these chemicals are within the plant vascular system. Contact pesticides that are on fruit and vegetable surfaces are removed to a significant extent by a good soak & wash with water along with some rubbing. Studies have also shown that the efficacy of water is almost the same as some of the tested vegetable washes. In fact, some studies suggest that 2-10% salt water or full strength vinegar are a bit more effective than plain water.
Each pesticide allowed in agriculture comes with a rated waiting period – typically number of days – from the point of application to crop to the point of harvest, by when most chemical applied disintegrates. For non-organic vegetables and fruits, it is important for the producers to comply with this waiting period but this is very hard to educate and enforce.
It goes without saying that Organic fruits and vegetables, when available, should be preferred since they are largely free of pesticide and fertilizer residues. Regardless, all fruits and vegetables, organic or inorganic, should be washed thoroughly before consumption, with water and possibly with salt solution and not necessarily requiring commercial washes.