Production of iron-enriched kale leaves (Brassica oleracea L. var. acephala) utilizing combinations of novel food processing technologies

Despite its rich content, iron bioavailability from leafy greens is low relative to protoporphyrin-bound (e.g. heme) iron, richest in red meat. We hypothesized that combinations of novel food processing techniques, i.e., vacuum impregnation (VI), water-bath (WB), overnight immersion (IM) in an iron sulfate solution, and moderate electric field (MEF) could improve kale leaf iron content and produce protoporphyrin-bound iron derivatives in situ. Combination MEF treatments increased leaf iron concentrations -160x greater than control. A ferroprotoporphyrin IX isomer was detected in MEF and IM-treated kale, providing up to 0.75 mg protoporphyrin-bound iron/100 g kale leaf fresh weight (FW). IM and MEF treatments also significantly increased leaf total chlorophyll concentrations -3x greater than the control. The novel food processing techniques employed herein produced kale with significantly higher concentrations of free + heme-bound iron, as well as total chlorophyll, relative to other plant-based sources. Future testing will determine if this "iron-enhanced" kale delivers more iron, as compared to other iron-rich food sources.