title: Novel in situ evaluation of the role minerals play in the development of the hard-to-cook (HTC) defect of cowpeas and its effect on the in vitro mineral bioaccessibility.
abstract: Cowpea is a nutritionally important drought-resistant legume in sub-Saharan Africa. It is, however, underutilised, in part due to the hard-to-cook (HTC) defect caused by adverse storage conditions resulting in seeds not softening during cooking. This study introduced a novel evaluation of the potential role that minerals play in the development of the HTC defect. The mineral distribution in the cotyledons of normal and HTC cowpeas were analysed by Proton Induced X-ray Emission (PIXE) spectrometry. The phytate, tannin and total phenolic contents were analysed together with in vitro mineral bioaccessibility. In HTC cowpeas, Ca and Mg were more concentrated in the cell wall-middle lamella area of the parenchyma cells. This, together with the reduction in phytate content, confirmed the 'phytase-phytate-mineral' hypothesis as a mechanism for development of the HTC defect. Despite the phytate reduction in stored cowpeas, the HTC defect decreased the bioaccessibility of Ca, Fe and Zn in cowpeas.
authors.affiliation: Department of Food Science and Institute for Food, Nutrition and Well-being, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa. Electronic address: johanita.kruger@up.ac.za.
authors.forename: Johanita
authors.initials: J
authors.lastname: Kruger
authors.affiliation: Materials Research Department, iThemba LABS, National Research Foundation (NRF), PO Box 722, Somerset West 7129, South Africa.
authors.forename: Roya
authors.initials: R
authors.lastname: Minnis-Ndimba
authors.affiliation: Materials Research Department, iThemba LABS, National Research Foundation (NRF), PO Box 722, Somerset West 7129, South Africa.
authors.forename: Christopher
authors.initials: C
authors.lastname: Mtshali
authors.affiliation: Department of Food Science and Institute for Food, Nutrition and Well-being, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
authors.forename: Amanda
authors.initials: A
authors.lastname: Minnaar
mesh_terms: D003296:Cooking; D007887:Fabaceae / Q000737:chemistry*; D008903:Minerals / Q000032:analysis* / Q000378:metabolism; D010833:Phytic Acid / Q000032:analysis; D012639:Seeds / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission
chemical_list: D008903:Minerals; D010833:Phytic Acid
keywords: Calcium; Cowpea; HTC; Hard-to-cook; In situ; Iron; Magnesium; Mineral bioaccessibility; PIXE; Phosphorus; Phytate; Proton Induced X-ray Emission spectrometry; Zinc