Which preposition to use with rawness

of Occurrences 8%

After the thickening is added, the gravy should just boil, to take off the rawness of the flour.

on Occurrences 1%

To take off the rawness on the upper side, hold the pan before the fire for a minute or two, and brown it with a salamander or hot shovel.

Which preposition to use with  rawness