Ultrasound assisted extraction of cadmium for decontamination of rice and its influence on structure/texture of cooked rice

Abstract

Cadmium (Cd) is a nonessential heavy metal and ranks seventh on the list of World Health Organization Agency's Toxic Substances. In this study, ultrasound assisted extraction (UAE) was used for Cd decontamination of rice grains and rice flour. Extraction conditions were developed [particle size, ultrasound (US) power, treatment time, temperature, pH, extraction solution volumes and treatment cycles] and applied for both low and high Cd contaminated rice. Under selected UAE conditions, 83% and 66% of total Cd were removed in just one cycle UAE treatment while over 93% Cd were removed after two and three-cycles for rice flour and rice grain, respectively. The total protein, total starch, pasting properties, thermal stability, morphology structure and textural properties of rice were evaluated after UAE treatment. Although a considerable amount of starch was lost during the UAE treatment (common to such treatments), UAE-treated cooking rice maintained good structural and textural quality. The pasting temperature was decreased with low damage to the morphology of starch granule. With several advantages like short treatment (20–30 min), rice good texture quality retention, simple and easy operation, low cost and applicability to rice grain and rice flour, the UAE process provides a very useful method for Cd removal contaminated rice.