Improvement of the content in bioaccessible lipophilic micronutrients in raw and processed drumstick leaves (Moringa oleifera Lam.)

Our objective was to evaluate the influence of cooking (boiling, steaming, frying) and processing (freezing, freeze-drying, sun drying, oven drying, sterilization or powdering) on the micronutrient profile of drumstick leaves (beta-carotene, lutein, a-tocopherol) and the bioaccessibility of the latter after in vitro digestion. Fresh drumstick leaves contain a high level of carotenoids and a-tocopherol with a very low bioaccessibility (<1%). Freezing, steaming and sterilization preserve the more the micronutrients and most of the processing methods improve the contents in bioaccessible beta-carotene, lutein and a-tocopherol. Among the cooking practices, only steaming was efficient to increase the compound release. The structural changes of the leaf tissue during processing partially explain the modulation of the bioactive compound release during the course of in vitro digestion. After boiling and steaming, the cells of epidermis and mesophyll were slightly disorganized while frying induced a deep destructuration of the overall tissue with cell wall rupture. (C) 2016 Elsevier Ltd. All rights reserved.