Light abrasive decortication of heavy metal contaminated quinoa and rice from southern Peru reduces lead and arsenic contamination, but not cadmium

Heavy metal (HM) contamination of grain crops is a potential health risk and removal of grain outer layers can reduce contamination to safe levels. This study investigated the reduction of lead (Pb), arsenic (As), and cadmium (Cd) using an abrasive decortication process in samples of quinoa and rice cultivated in southern Peru, where HM contamination has been reported. Outer layers of different varieties of quinoa and rice grains were incrementally removed (5, 10, 15 s), and HMs were determined using inductively coupled plasma mass spectrometry (ICP-MS). Cryo-scanning electron microscopy (cryo-SEM) images for quinoa and rice grains showed elements with high atomic number around the outer layers of the grains that were mostly removed upon decortication. Pb and As concentrations in quinoa INIA-415 Pasankalla were completely removed in 5 s of decortication, while in other samples Pb decreased gradually from 100 to 0% within 15 s. With decortication, As in one rice type (RTL2) was decreased by similar to 35% to meet the Codex General Standard limit. Cd was not significantly reduced by decortication due to its more uniform distribution in the grains. Thus, in quinoa and rice grains, Pb and As, but not Cd, can be significantly decreased through abrasive decortication.