The Combination Effects of Immersion and Moderate Electric Field (MEF) Treatments on Enhancement of Deliverable Iron From Kale Leaves (Brassica oleracea L. Var. Sabellica)

Abstract

Abstract Objectives Due to anti-nutrients found in leafy greens and the physical-chemical properties of inorganic iron found in plant sources, iron bioavailability is lower relative to heme iron rich in red meat. We tested a series of novel food processing techniques (i.e., vacuum treatment, bath-immersion, and moderate electric field (MEF) to improve iron content and potential delivery, using kale (Brassica oleracea L. var. sabellica) as our model green leafy vegetable. Methods A ferrous sulfate (FeSO4) solution was prepared and fresh kale samples (n = 3 per treatment) were immersed in the solution alone (control), treated with vacuum alone, vacuum + water bath (30–50°C), or vacuum + water bath + MEF (15 V/cm at frequency of 60 Hz at 40–60°C) for up to 15 min. Effects of immersion (24 h at 4°C) after each treatment step were also tested. Treated samples were rinsed in deionized water before freezing and lyophilization prior to analysis. Concentrations of chlorophyll and iron chlorophyll derivatives were measured in both lipophilic and polar leaf extracts using ultra high liquid chromatography-diode array detection (UHPLC-DAD). Atomic absorption spectrometry was used to measure iron concentrations. Differences between treatment groups were analyzed with one-way ANOVA, followed by Tukey's posthoc testing for pairwise comparisons (P < 0.05 considered statistically significant). Results Vacuum followed by immersion produced kale with ∼1500x more iron than the kale control, while MEF-treated kale had the greatest increase in iron concentration without immersion (∼4000x than control). Two novel metabolites, tentatively iron chlorophyllin derivatives, were observed in the lipophilic extracts of the MEF and immersed kale samples, and identifies are being pursued via UHPLC-high resolution mass spectrometry metabolomics. Conclusions The novel food processing techniques employed here produced kale with iron concentrations significantly higher than the kale control, as well as other iron-rich plant foods (e.g., ∼40x times higher than black beans). Future testing will determine if this” iron-enhanced” kale has the potential to better deliver iron as compared to untreated kale, an FeSO4 supplement, or a heme-rich source. Funding Sources This research was supported by OARDC via a SEEDS grant and also via Hatch #W4122.