(P17-030-24) Effects of Food Processing on Iron and Its Bioavailability in Sweet Corn

Objectives: Sweet corn is one of the most consumed vegetables in the US. In this study, we measured the effects of post-harvest handling, food processing (cooking and industrial processing) and storage on sweet corn iron content and bioavailability.

Methods: Fresh bi-color sweet corn was harvested from the field and processed into samples representing two major retail types (farmers market and grocery store), two common cooking methods (boiling and steaming) and two industrial processing methods (freezing and canning). Frozen and canned corn were stored for one month. All samples were lyophilized before analysis. Three cornmeal samples were included as comparisons. Iron was measured in all samples by ICP-ES. Iron bioavailability was assessed by an established Caco2 cell bioassay that utilizes cell ferritin formation as a marker of Fe uptake. A “relative bioavailability factor” (RBF) was calculated by dividing the bioavailability value by iron content.

Results: Fresh sweet corn contained 17.27 µg/g (dry weight, DW) iron. Post-harvest handling and food processing did not alter iron contents. The iron concentration significantly reduced to 14.35 µg/g DW in canned corn after one month storage. Iron bioavailability of fresh and processed sweet corn ranged from 85.54 ng ferritin/mg total cell protein in canned corn stored for one month to 122.81 ng ferritin/mg total cell protein in fresh corn. Non-fortified cornmeal sample had similar amount of iron to sweet corn samples, but the two fortified cornmeal samples contained much more iron at 36.05 and 45.11 µg/g, respectively. RBFs of fresh and post-harvest handling sweet corn samples were from 6.45 to 7.11. While RBFs of heat-treated sweet corn samples were generally lower than 6.0. The only exception is frozen off the cob and stored for 1 month, whose RBF was 6.62. Despite the comparable or higher iron contents in cornmeal samples, their RBFs were much lower, only ranging from 1.07 to 1.86.

Conclusions: Post-harvest handling and food processing did not alter iron contents in sweet corn, except in canned corn samples that were stored for one month. Heat tended to reduce iron bioavailability in sweet corn. Sweet corn displayed a very higher iron bioavailability, and it could be a good food source to address increased prevalence of iron deficiency in the US.

Funding Sources: USDA