The proximate composition of black and red rice is presented in
Table 1. The polishing treatment (12% DOM) used in the present
study promoted a decrease of 16.2% and 6.2% in the protein content
of black and red rice, respectively. Moreover, there was a further
decrease in the protein content of both parboiled unpolished black
rice and parboiled unpolished red rice when compared to their
respective non-parboiled unpolished rice, indicating that parboiling
process promoted the leaching of proteins from the grains to
the soaking water. This decrease was similar (p 6 0.05) between
both rice cultivars. The parboiled polished red rice presented
14.5% higher protein content than polished red rice. On the other
hand, no difference (p 6 0.05) was determined in the protein content
of parboiled polished black rice as compared to polished black
rice. These results indicate that the proteins of red rice migrated
from the bran layers of rice caryopsis to the inner layers of the
grains during soaking step of parboiling more than the proteins
from black rice.