Iron and zinc biofortification and bioaccessibility in carrot ‘Dordogne’: Comparison between foliar applications of chelate and sulphate forms

Abstract

Hidden hunger is a worldwide problem, with iron (Fe) and zinc (Zn) deficiency being the most common causes of mineral deficiency. Vegetable biofortification is an effective strategy to fight mineral deficiency, especially when commonly consumed vegetables are utilized, as in the case of carrots. This biofortification study aimed to investigate the response of the off-season carrot cv. Dordogne to different forms of foliar applications of Fe and Zn. The crop received four applications of both minerals, either in the form of inorganic salt (FeSO4 and ZnSO4) or chelated forms (Fe-DTPA and Zn-EDTA), at a concentration of 6 mM of these elements. FeSO4 was efficient in increasing the Fe concentration in carrots (by 52%), while Fe-DTPA caused no significant differences. Regarding Zn, both forms were effective in the biofortification, but Zn-EDTA proved to be more efficient in increasing root Zn concentration (+94%) than ZnSO4 (+57%). Bioaccessibility data, measured after in vitro digestion, showed that biofortified carrots with the chelated forms retained a full bioaccessibility of the minerals (around 100% as in control carrots). However, the sulfate-biofortified carrots showed reduced bioaccessibility values (60% and 80% for Fe and Zn, respectively). The results also showed an increase in dry matter, total nitrogen content and antioxidant activity in plants treated with Zn-EDTA. This trend paralleled the increase of polyphenols and total carotenoids content, suggesting the overall benefit of biofortification strategies conducted in the field. In conclusion, our study revealed that chelated forms of both minerals are preferable in the biofortification programs of carrots.