L.S.
Have you tried either ignoring the problem or reverse psychology? My 17 month old throws food on the floor all the time too and it seems that if I just ignore her when she does it she doesn't do it as much. It's like a challenge for her. I haven't tried reverse psychology but I just read about it in "What to expect: the toddler years" book. They say to tell they the opposite of what you want them to do and then they think they are disobeying and they do it and you get what you want. It's a win-win situation. And it doesn't effect their psychological development. Good Luck!