The use of sodium bisulfite during the soaking step of
parboiling, at the lowest concentration used in the present study
of 0.2%, was able to significantly (p < 0.05) promote a whiter colour
of parboiled rice, a decrease in the percentage of stained grains, and
an increase in the percentage of completely gelatinized grains
compared to untreated parboiled rice. Moreover, the cooking time
of parboiled rice treated with up to 0.6% sodium bisulfite was
similar than the cooking time of both non-parboiled rice and
parboiled rice without sodium bisulfite treatment. However, the
reduction of thiamine by sulfite is a risk associated with the
treatment. Therefore, careful consideration needs to be given to the
risks vs. benefits derived from the use of sodium bisulfite during
parboiling of rice. Further studies, including thiamine fortification
and in vivo animal studies are recommended to ensure the safe use
of sulfite in parboiled rice.