AFAIK, there is no entity of common foods for NLTK or similar. It's quite likely you have to construct a list for yourself.
But, thankfully, the internet is your friend, here are a few good sources to start with that cover a lot of common vegetables and fruits in the English-speaking world:
- http://vegetablesfruitsgrains.com/list-of-vegetables/
- http://edis.ifas.ufl.edu/features/fruitvegindex.html
- http://www.enchantedlearning.com/wordlist/vegetables.shtml
Good luck!
