Carotenoid Stability during Dry Milling, Storage, and Extrusion Processing of Biofortified Maize Genotypes

Translation of the breeding efforts designed to biofortify maize (Z. mays) genotypes with higher levels of provitamin A carotenoid (pVAC) content for sub-Saharan Africa is dependent in part on the stability of carotenoids during postharvest through industrial and in-home food processing operations. The purpose of this study was to simulate production of commercial milled products by determining the impact of dry milling and extrusion processing on carotenoid stability in three higher pVAC maize genotypes (C17xDE3, Orange ISO, Hi27xCML328). Pericarp and germ removal of biofortified maize kernels resulted in similar to 10% loss of total carotenoids. Separating out the maize flour fraction (< 212 mu m) resulted in an additional similar to 15% loss of total carotenoids. Carotenoid degradation was similar across milled maize fractions. Dry-milled products of Orange ISO and Hi27xCML328 genotypes showed similar to 28% pVAC loss after 90-days storage. Genotype C17xDE3, with highest levels of all-trans-beta-carotene, showed a 68% pVAC loss after 90-day storage. Extrusion processing conditions were optimal at 35% extrusion moisture, producing fully cooked instant maize flours with high pVAC retention (70-93%). These results support the notion that postharvest losses in maize milled fractions may be dependent, in part, on genotype and that extrusion processing may provide an option for preserving biofortified maize products.