Effects of rinsing and cooking methods on concentration of heavy metals (Pb, Cd, Ni, Cr) in rice

Rice is one of the world's most commonly consumed cereals. Consequently, its contamination by food contaminants, including heavy metals, should be taken into consideration. The purpose of this study was to determine the level of heavy metal contamination in rice samples of Hashemi cultivar harvested randomly from three areas of Masal, Shanderman, and Soomehsara in the west of Gilan province. In the second stage, the effect of two factors of soaking time of rice before cooking and cooking method (drained and boiled) on changes of heavy metals in consumed rice was evaluated. Following the preparation and digestion steps, the concentration of heavy metals (lead, cadmium, chromium and nickel) was determined using induced plasma mass spectrometry (ICP-MS). The results showed that in comparison with the other two regions and the standard limit, the concentrations of Cr and Ni in rice harvested from the Shanderman region (with 2.1 and 1.35 ppm, respectively), were significantly higher contamination. The results showed that washing and soaking the rice were very effective in reducing the heavy metal content. Moreover, cooking rice using the drainage method was more effective in reducing the concentration of heavy metals than the boiled method. Due to the difference in the effect of soaking treatments and different sintering methods in reducing the concentration of metals, using a combination of 3 consecutive washes and 6 hours of soaking and cooking in both methods is introduced as the most effective treatment in reducing the concentration of heavy metals.