<<Disclaimer: Verify this information before applying it to your situation.>>

I understand that not all brands of grated cheese are considered to GF,
but I'm not sure why.  We use Sargento GF brands at home, but I am
wondering about having grated cheese when eating out.  Is it the annatto
color (which I believe is a not clearly a problem)?  If so, what may be the
problem with grated white cheeses like mozzarella?