Rice and maize are two stable crops commonly consumed in Latin America where zinc deficiency is common. Improved biofortified varieties contain higher levels of zinc, but not much is known about the effect on zinc retention or on phytate reduction when using these crops in common recipes. Therefore we studied the effect of polishing and processing on zinc and phytate concentration in high zinc rice and common recipes on zinc concentration in high zinc maize.
Advanced breeding line of upland rice was grown at CIAT, Colombia, polished for 0, 5, 10, 15 and 20 seconds and cooked. For maize, an advanced hybrid breeding line was grown at CYMMIT, Mexico. From this maize two types of tortillas were made (with and without nixtamalization) and a toasted flour was made. Zinc concentration was measured by ICPMS at CYMMIT Mexico for maize and at Flinders University in Australia for rice as well as phytate concentration by LC.
Zinc concentration in rice was 24mg/kg (sd=0.13) in raw rice and reduced linearly with milling time to 19mg/kg (sd=0.22) after 20s polishing and cooking (retention 79%). Phytate concentration reduced from 9.5mg/g (sd=1.3) to 1.2 mg/g (sd=0.1) (13% retention). Zinc concentration in biofortified maize was 33 mg/kg in uncooked maize and 15 mg/kg in conventional maize. Processing into tortilla or toasted flour did not reduce zinc concentration and nixtamalization added 2 mg of zinc.
Foods made of biofortified rice and maize have high zinc retention and therefore have the potential to reduce zinc deficiency in humans.