Hahah- that's why I don't draw food- I'd end up licking the page ;)
I've used a light bit of graphite over the colour to add some shade in, and it works quite well - as long as the amount of colour on the paper doesn't feel too waxy so they graphite doesn't 'stick' to the paper. Definitely one to play with in a sketchbook first!
And yes, definitely steer clear of any unidentified mushrooms! :)
E x