ABSTRACT
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.
CHAPTER ONE: INTRODUCTION
Background of the Study
Micronutrient deficiencies among women of reproductive age remain a major health related challenge to reckon with in many Sub-Saharan Africa countries (Andersen, Thilsted, Nielsen, and Rangasamy 2003; Kamga, Kouamé, Atangana, Chagomoka, & Ndango 2013). Adequate nutrition before the reproductive years, proper adolescent growth, sufficient nutrient stores and specific interventions of folic acid and multivitamins supplements during pregnancy, nutrition education and healthy diet programmes have been emphasized during the different stages of women of reproductive age that is during infancy, adult life, preconception period, pregnancy and during the lactating stage (Islam, 2010).
Adequate micronutrient status of women of reproductive age is critical since it is required during adolescence, pregnancy and in lactation. Micronutrient intake by women of reproductive should be maintained to prevent depletion of body nutrient reserves during stages of vulnerability of pregnancy and lactation (Darnton-Hill & Mkparu, 2015). Micronutrient deficiencies amongst women of reproductive ages can cause major consequences such as reduction in breast milk nutrient concentrations Kamga et al . While many government and non- government agencies are emphasizing on the nutritional status of women of reproductive age (pregnant and non-pregnant) very little is being done to ensure that lactating women achieve optimal nutrition status (World Health Organization & UNICEF 2003).
The consumption of African Leafy vegetables (ALVs) that are accessible to the low- income communities offers opportunity for improving micronutrient status and food
security of many poor families whose health and nutrition are at risk (Raneri et al., 2019)
Three ALVs; Pumpkin, Fig-leaf, and Stinging nettle have been widely used both as dried and fresh vegetables to make mukimo a mixture of boiled potatoes and green maize together with the vegetables in Kenya. This is a common practice among the Kikuyu community who are also the majority in the Kiambu County in Kenya as noted by Chivenge et al. (2015). This study sought to investigate the nutrient retention and sensory evaluation of three (ALVs) i.e. Pumpkin, Fig- leaf, and Stinging nettle after applying different heat treatments of solar drying, blanching, and cooking. The sensory evaluation was assessed among women of reproductive age in Kiambu, County, Kenya. Pumpkin, Fig-leaf, and Stinging nettle were selected in this study due to their local availability and common consumption among residents of the proposed study area. Vitamin C has an important role in collagen synthesis, wound healing, prevention of anaemia and also an oxidant. It is also known to increase bioavailability of dietary non – haem iron which is an important in WRA who are at risk of iron deficiency anaemia (Bries, 2017).
Problem Statement
Vitamin A, iron and zinc are currently the micronutrients of greatest public health concern among Kenyan vulnerable groups including women of reproductive age (Harika et al., 2017). Although many studies have reported high nutritional value of ALVs, their production and utilization have not been optimized especially in areas where they are not naturally grown (Mavengahama, 2013). The main impediments in the utilization of ALVs appear to be the low availability due to seasonality and post-
harvest wastage occasioned by their high perishability (Negi & Roy, 2001 & Gupta et al., 2013).
A recommendation by Sheetal Gupta et al (2013) emphasizes the need to explore appropriate ways that can be adopted by rural communities to preserve leafy vegetables for use during dry spells when production plummets and popularizing them among women of reproductive age. Another challenge in the consumption of these ALVs has been the limited data on different varieties of ALVs in terms of their nutrient composition, little knowledge being passed from those with more knowledge concerning ALVs to those with less knowledge. Most of the studies on pumpkins are compositional studies conducted both on flesh and pumpkin seeds hence data on nutritional content of the pumpkin leaves is scarce.
Currently, we have limited data on studies conducted on the nutrient content of the fig–leaf gourd. In regard to the stinging nettle several studies have been conducted on the medicinal value of the plant but there is limited data on the nutritional composition of stinging nettles (Dar et al., 2013; Namazi et al., 2003;Kregiel, Pawlikowska, & Antolak 2018). Some of the ALVs species have also disappeared locally while the consumption of others has been despised by the modern people (Abukutsa-Onyango 2003). There is also limited data on the effect of various drying methods on the quality of ALVs in Kenya; information’s which is necessary to establish suitable drying methods for the cultivated leafy vegetables within Kenya (Gockowski, Mbazo’o, Mbah & Moulende, 2003).
This study therefore seeks to investigate the effect of solar drying, blanching and cooking on the content of iron, zinc, and β- carotene (pro–Vitamin A) in Pumpkin
leaves (Curcubita maxima), Stinging nettle (Urtica dioica), and Fig-leaf gourd (Cucumis ficifolius).
Purpose of the Study
The overall aim of this study was to evaluate the effect of solar drying and cooking treatments before and after blanching on the nutrient (vitamin C, β-Carotene, iron, and zinc) retention in three ALVs namely pumpkin leaves (Curcubita maxima), stinging nettle (Urtica dioica) and fig- leaf gourd (Cucurbita ficifolia) and their sensory evaluation among women of reproductive age in Kiambu County.
Objectives of the Study
- To analyze the nutrient (β- carotene, vitamin C, iron, and zinc) content of fresh and cooked fresh ALVs.
- To assess the nutrient content of solar dried fresh and solar – dried blanched ALVs
- To evaluate the sensory properties of both cooked fresh and cooked solar dried ALVs.
- To determine the effect of different combinations of blanching, cooking and solar drying treatments on the nutrient retention of the ALVs.
Study Hypotheses
H01 There is no significant difference between iron and zinc content of the fresh and solar dried of the selected ALVs.
H02 There is no significant difference between the β- carotene and vitamin C content of the fresh and solar dried of the selected ALVs.
H03 There is no significant effect of cooking and blanching on nutrient content of cooked solar dried of the selected ALVs.
H04 There is no significant difference in the sensory evaluation between the cooked fresh and cooked solar dried of the selected ALVs.
Significance of the study
The finding from this research may be useful in supporting nutritional education programs at health facility level during nutrition counseling or in community forums that seek to popularize the consumption of ALVs especially to lactating mothers who are usually left out in most programs that address micronutrient deficiencies. The study has generated data, which may be of use to the food industry in making decisions regarding to commercial processing of these vegetables. The study provides information that will be used to update the Kenya food composition table. The result from the study on acceptability of ALVs will be useful for promotional and intervention activities. The finding from this research can be used as a basis for further research.
Limitations of the Study
The quantity of the nutrient contents in the three selected ALVs may be affected by such factors as the source of the plants, soil conditions, maturity stage at harvest and postharvest handling that were not investigated in this study.
Delimitations of the Study
The study researched on three African leafy vegetables i.e. (pumpkin leaves (Curcubita maxima), stinging nettle (Urtica dioica) and fig-leaf gourd (Cucurbita ficifolia) with regard to trace minerals iron and zinc and also nutrients vitamin A and
C of greatest concern to public health This however does not underscore the importance of other micronutrients in the diet.
Assumption of the Study
The study assumed that all the three purchased African Leafy Vegetables from Kiambu markets were grown from the same area.
Conceptual Framework
The conceptual framework of this study was based on the fact that the perishable nature of the ALVs makes them susceptible to huge postharvest losses and wastage, which coupled with their seasonality lead to low availability during the off-season (Fasuyi, 2006). This compounds the problem of food shortage. Scarce information on the nutritional value of most of these vegetables may contribute to their low consumption (Chivenge et al., 2015). In addition, low consumption could be an issue related to sensory attributes as affected by various postharvest processing/preparation treatments (Raneri et al., 2019). Figure 1.1 shows the conceptual framework generated by the researcher to illustrate the interrelationships between variables that will lead to higher availability of micronutrients to women of reproductive age.
