Rice is a staple food for more than half of the world’s population. The parboiling process is known to
increase the nutritional value of milled rice, but the process darkens the grains, with a corresponding
negative effect on consumer acceptability. The aim of this study was to evaluate the effects of using
different concentrations of sodium bisulfite (0, 0.2, 0.4, 0.6, 0.8, 1.0%) during the soaking step of rice
parboiling process on the thiamine content and technological properties of parboiled rice. Moreover, the
residual sulfite content in parboiled grains was also evaluated. The lowest concentration of 0.2% sodium
bisulfite was able to significantly (p < 0.05) promote a whiter colour, a decrease in the percentage of
stained grains, and an increase in the percentage of completely gelatinized grains in the parboiled rice,
compared to rice without sodium bisulfite treatment. However, the use of sodium bisulfite significantly
(p < 0.05) reduced the thiamine content, which is considered a risk associated with the treatment.