Effect of Parboiling on Fluoride Content of Rice

In several endemic fluorotic zones of rural India, home-made parboiled rice is the main staple. Studies were therefore conducted to investigate whether any relationship exists between the concentration of fluoride in the water used for parboiling paddy, and in the parboiled rice. Parboiled rice (PBR) was prepared in the laboratory using water from different origins (rivers, open wells, tube wells and ponds) collected from normal and fluorosis affected regions. The effect of (a) parboiling, (b) polishing, and (c) cooking, on the fluoride (F-) content of rice was studied, using two local varieties of paddy, namely, HANSA and SONA. Fluoride levels of PBR and raw rice collected from the local markets of Hyderabad city were also measured. Results show that: 1) parboiling paddy using water containing fluoride either added or present originally resulted in a significant increase in the Fcontent of rice, irrespective of the source of water used; 2) this increase was directly proportional to the levels of Fin water (r = 0.96); 3) polishing PBR to 5% level reduced the Fcontent of rice by about 30%; 4) on cooking the PBR in the same source of water which was used for the parboiling, a cumulative 2to 8-fold increase was observed in the Fcontent of the cooked PBR; and 5) even in the market samples, PBR had significantly more Fthan raw rice. This study reveals the importance of using only water with permissible limits of Ffor parboiling and cooking. It also highlights the importance of food fluoride in the etiology and control of endemic fluorosis.