Probably, leaching of pigments in the cooking water and diffusion of pigments
from the rice surface towards the endosperm during cooking
may also contribute to the colour of cooked rice. It
seems that the effect of difference in water uptake on the
pigment concentration was partly compensated by a
decrease in leaching and/or diffusion of pigments with
increasing DOM during rice cooking, as the redness of
the cooked rices with residual outer endosperm
(9% < DOM < 15%) remained constant. Also, after bran
and outer endosperm removal (DOM > 15%), the brightness
and redness of the cooked rice kernels remained constant,
while the yellowness slightly decreased with
increasing DOM. The latter is in contrast with the observations
for raw rice kernels, which showed a constant yellowness
in the middle endosperm. Furthermore, the colour
trends of the middle endosperm (15% < DOM < 25%) of
the cooked rice kernels are similar to those of the outer
endosperm.