Enhancing the nutritional value of Portulaca oleracea L. by using soilless agronomic biofortification with zinc.

Zinc (Zn) plays a crucial role for human health. Zn deficiency is a common problem worldwide, causing health problems specifically related with detrimental effects on immune system. In this study we used hydroponic floating system and nutrient solutions (NS) with different levels of Zn (0.13 - control, 1.3, 2.6 and 5.2 mg/L Zn) in order to test a biofortification process aimed to increase the Zn tissue content of two different varieties (commercial and wild) of purslane. We evaluated the effects of the treatments on yield, visual and overall nutritional quality of the edible part of plants. Biofortification treatments did not affect plant yield, but increased the Zn content in the edible part of purslane by 1.8, 2.3 and 2.7-fold, respectively with 1.3, 2.6 and 5.2 mg/L Zn in the NS, so that the consumption of a serving portion of 150 g of baby leaf purslane biofortified with the highest Zn concentration would account for 21% of RDA (recommended daily allowance) for this nutrient. The Zn biofortification process did not affect colour parameters, therefore no differences in the product visual quality were observed. Zn treatment with 5.2 mg/L allowed to obtain an increase in neoxanthin, lutein and β-carotene, while it was not possible to outline a common trend for the fatty acids profile in relation to the Zn treatments. The consumption of hydroponic purslane biofortified with Zn may allow to improve the Zn nutritional status of consumers, and provides different important phytochemicals, such as carotenoids and unsaturated fatty acids.