Nutrient Retention and Sensory Acceptability of Solar-Dried African Leafy Vegetables Among Women of Reproductive Age, Kiambu County, Kenya
Muniu, John Gachoya
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Micronutrient deficiencies pose major health challenges in many African countries with certain population groups such as women of reproductive age being at a greater risk. African leafy vegetables form part of local agricultural biodiversity and have been part of the daily livelihoods of the local populations for many years. These vegetables hold promise in addressing micronutrient deficiencies if their supply and consumption are scaled up through the right application of appropriate postharvest technologies. The study adopted an experimental design to determine the retention of iron, zinc, β-carotene and vitamin C as well as sensory acceptability in three African Leafy vegetables; i.e. pumpkin leaves (Curcubita maxima), Fig-leaf gourd (Cucurbita ficifolius), and stinging nettle (Urtica dioica) subjected to various processing treatments including solar drying, blanching and cooking. About 10kg of fresh vegetables randomly sampled were purchased from Kiambu market, transported using cool box at 150C to Kenyatta University, appropriately packed and stored at 50C for processing and analysis. Solar drying was carried out using a locally fabricated solar dryer, blanching was done at high temperature (80-1000c) for 5 minutes and cooking was done using ohms model electrical cooker with four plates set at medium temperature 1650C for 15-20 minutes. Iron and zinc were quantified using Atomic Absorption Spectrophotometer while β-Carotene and Vitamin C were quantified using Reverse Phase High Pressure Liquid Chromatography. All determinations were carried out in triplicate and mean values computed. Sensory evaluation was determined using the 9-point hedonic scale questionnaire administered to a sample of 30 women of reproductive age purposively selected from Kiambu County. Pumpkin leaves had the highest iron content amounting to 29.33 ± 0.474 mg/100g dw followed by Fig-leaf gourd at 25.38 ± 0.06 mg/100g dw. Fig-leaf gourd had the highest content of zinc at 5.51 ± 0.08mg\100g dw followed by pumpkin leaves at 3.307 ± 0.055mg\100g dw. Stinging nettle leaves had the highest pro-vitamin A (β- carotene) content of 34.69± 0.14 mg/100g dw followed by pumpkin leaves. Vitamin C concentration was highest in stinging nettle leaves 228.60±1.81mg\100g dw followed by Fig-leaf gourd 122.59 ± 0.09 mg\100g dw while pumpkin leaves had the lowest content 118.73 ± 0.15mg\100g dw of the vitamin. Both blanching and cooking had significant effect on the content of both minerals and vitamins in the leafy vegetables. Solar drying caused significant reductions (p ≤ 0.05) in the levels of vitamins in the vegetables, but it did not significantly change their mineral contents. Solar drying had the best retention of iron, zinc, and vitamin C. Vitamin A was well retained during heat treatments but was sensitive to solar drying. Vitamin C suffered the heaviest losses in all processing treatments. Highest retention of nutrients was achieved in Fig-leaf gourd compared to pumpkin leaves and stinging nettle leaves. Pumpkin leaves were given the best sensory rating among cooked fresh vegetables, while stinging nettle leaves was the most acceptable among solar-dried cooked vegetables. Cooked fresh vegetables were more acceptable than the cooked solar-dried ones except for stinging nettle leaves where the reverse was true. The study reveals that pumpkin leaves, Fig-leaf gourd and stinging nettle leaves are important sources of key nutrients after solar drying, blanching and cooking with a good retention of this nutrients. The study therefore recommends popularization of the solar dried ALVs as key sources of micronutrients.