What is the best way to wash broccoli and remove germs?

I feed my kids fresh broccoli every day at lunch. I rinse it off with warm tap water and that seems to do reasonably well at removing germs. 

Fresh Broccoli

For this experiment, I wanted to determine if simply rinsing in tap water did a good job cleaning broccoli. First, I rubbed an unwashed piece of broccoli on one half of an agar plate. 


Then I rinsed another piece of broccoli under WARM tap water for 20 seconds. I rubbed it while I was rinsing it.


I rubbed the rinsed broccoli onto the other half of an agar plate. The plates were incubated overnight.


The results show that just rinsing in WARM water and rubbing does a good job cleaning broccoli.  I have repeated this experiment a few times and warm water is more effective than cold water.


Negative Control

I wanted to make absolutely certain that my tap water and clean gloves were not contributing bacteria to my experiments. So, I put on a clean pair of gloves, got them wet under the tap water, and rubbed them on a clean agar plate. I do this control for all of my fruit and vegetable washing experiments. 


I incubated the plate overnight and was pleased that there was no bacterial growth at all the next day.