Effects of the pre-cooking process using acetic acid and citric acid on lead concentration in rice

Abstract

Rice is one of the most highly consumed foodstuffs in the world. In keeping with this, produced rice of many regions of the world contains high lead content. The present research was done to study the effects of the pre-cooking process of rice with acetic acid and citric acid on the concentration of lead. Rice samples were divided into 5 different pre-cooking treatment groups of soaking in acetic acid 1% and soaking in citric acid 1% (2 hrs), boiling with acetic acid 1% and boiling with citric acid 1% (20 min) and finally 6 times rinsing with deionized water. Then, measurement of lead remains was done using an atomic absorption optical spectrometer equipped with a detector of graphite furnace with deuterium lamp. The mean concentration of lead in primary rice samples without any processing operation was 87±4.8 ppb. The mean concentration of lead in rice samples processed with soaking in acetic acid, soaking in citric acid, boiling with citric acid, boiling in acetic acid and finally 6 times rinsing with deionized water were 55±3.8, 14±1.6, 32±2.4, 14±1.1 and 30±0.5 ppb, respectively. The highest reeducation percent of lead in rice samples was obtained in both soaking with citric acid and boiling with citric acid (84%). In keeping with the high concentrations of lead in studied rice samples, obtained concentrations were lower than the allowed limit of lead announced with the international standard organization of Iran (150 ppb). Boiling and soaking of rice samples with citric acid 1% can be a convenient and fast way to reduce the concentration of lead in rice samples.