Is this really necessary to wash our fruit and vegetables before we eat them? And what does science have to say about washing produce?
There are lots of bugs, bacteria and diseases that like to live on raw fruit and vegetables. Salmonella, campylobacter, listeria, and strains of E coli have all been found on fresh produce, and though very rarely fatal, there are some noted exceptions.
In Germany in 2011, for example, 53 deaths were reported as the result of anaemia and kidney failure brought on by E coli consumption from fenugreek sprouts (4000 people fell ill after eating the sprouts in total). That same year in the US, 30 people also died from listeria after eating cantaloupe melons.
In New Zealand they generally only have "scares" with suspected contamination and subsequent precautionary recalls, such as the 2014 hepatitis A warning which concerned some Royal Gala/New Zealand Beauty apples and Golden Queen peaches.
Nasty bugs
Scientifically speaking, the evidence concerning the effectiveness of washing produce is weak. There are no large studies out there that tell us whether real nasties like E coli or hepatitis A can really be washed off fruit or vegetables with water. It is believed many of these harmful bugs are water-resistant, and while your risk will be minimised with washing, it won't be eliminated.
The only scientifically-proven way to kill certain bacteria and diseases is to cook them – something that happens to processed fruit and vegetables when sold in cans. Part of the enjoyment of eating fresh produce, however, is its raw freshness. Canned food aside, cooking isn't an option for many items – including most fruit.
As indicated via the German and American outbreaks, melons and sprouts are two of the items of fresh produce most likely to harbour bacteria. Research has found that it is the porous rind of the melon that pathogens like to attach to, and from there they can internalise. Sprouts are also susceptible to internalised bacteria, which can become protected in a biofilm on the sprout surface.
Any produce with skin on it (like a tomato or an apple) will likely also have a porous outer shell, but most can be kept safe with a shower of cold water. Produce without such porous surfaces, like lettuce or spinach, carry little risk. Again, there are no guarantees, so washing (or buying pre-washed) is always highly recommended.
Though it may seem a good idea, scrubbing food items with a brush may actually put you in more danger, particularly if they're not eaten straight away. When you scrub produce with a brush you make it prone to spoilage and weeping. It will release fructose which can support pathogen growth, potentially making its surface prime for bacteria formation.