Depends on which meaning that you put in the word "hero". I have the same opinion as ukimix, Shokugeki no Soma doesn't have a hero or heroine.
However, thinking about Erina I should say that she is more a vilain than anything else.
Firstly, welcome Chingaruna517! I hope that I you have fun in the forum, and principally here in the Shougeki section.
Well, after almost two months I changed my mind a bit, seeing Tadokoro getting highlight she looks more a heroine now than before, she is who evolve more with Souma. I think she is near to look like a heroine in the series and I hope that Autumn Election arc strengthen this impression. A heroine is a character who you cheer up to, and she is this to me.