Can consumption of local micronutrient- and absorption enhancer-rich plant foods together with starchy staples improve bioavailable iron and zinc in diets of at-risk African populations?

Iron and zinc deficiencies remain prevalent in developing countries, often due to monotonous starchy diets that are low in bioavailable minerals. This review addresses the question as to whether consumption of starchy staple foods in Africa together with micronutrient-dense and absorption enhancer-rich plant foods can enhance iron and zinc bioavailability in the diets of at-risk populations. While green leafy vegetables (GLVs) fortification of starchy staples can improve mineral contents, especially iron, it may not improve bioavailable iron and zinc, due to GLVs' high contents of mineral absorption inhibitors, notably polyphenols, phytate and calcium. Fruits, although low in minerals, could improve bioavailable iron and zinc in the staples because of their high ascorbic and citric acid and/or ß-carotene contents, which can form soluble chelates with the minerals. More human studies are needed to establish whether such a technology or fortification strategy can improve bioavailable iron and zinc in African-type plant-based diets.

Effect of drying methods on chemical composition and antioxidant activity of underutilized stinging nettle leaves.

Stinging nettles provide low-cost quality nutrition for alleviating malnutrition. Previous research on stinging nettles focused mainly on the nutritional quality of fresh leaves. In this study, the effect of drying method on macronutrients, mineral content, ascorbic acid, ß-carotene content and total phenols content and antioxidant activity were investigated. The contribution of fresh, oven dried or freeze dried stinging nettle leaves to the required daily value for the nutrients were also determined. Oven drying of nettle leaves resulted in a higher loss of ß-carotene and ascorbic acid content compared to freeze drying. In contrast, the total phenols content and total antioxidant activity were higher in oven dried stinging nettle leaves compared to freeze dried leaves. Overall, freeze dried and oven dried nettle leaves can be considered as a rich source of Ca, Mg and vitamin A; a good source of vitamin C, Fe, and Mn; and a source for Mg and K. Stinging nettle leaves could potentially be used as a cheap natural source of antioxidants and for addressing micronutrient malnutrition.

Encapsulation and antioxidant activity of ascorbyl palmitate with maize starch during pasting.

Ascorbyl palmitate can interact with amylose to form amylose-lipid complexes. This study determined the effects of ascorbyl palmitate (0, 15 and 50mg/g starch) on the pasting properties of maize starch, amount of ascorbyl palmitate bound in the starch paste, release of ascorbyl palmitate after enzymatic hydrolysis and its antioxidant activity. Pasting of starch with ascorbyl palmitate at 91°C for 120min resulted in the formation of type II amylose-lipid complexes as shown by DSC melting enthalpies. About 93% and 66% of ascorbyl palmitate were encapsulated when 15mg and 50mg was respectively added to maize starch during pasting. Less than 50% of the bound ascorbyl palmitate was released during pancreatic α-amylase hydrolysis suggesting that some of the complexes were not hydrolysed to release the ligand. The antioxidant activities of the ascorbyl palmitate correlated (R=0.937) to the amount released during enzymatic hydrolysis. It can be concluded that pasting of maize starch can be used to encapsulate ascorbyl palmitate by possibly forming amylose-lipid complexes.