Comparative Nutritional Analysis Of Tylosema Esculentum (Marama Bean) Germplasm Collection In Namibia

ABSTRACT

Purpose of the research: Malnutrition is a medical condition caused by an unbalanced diet, typically characterised by stunting, wasting and underweight in children. Worldwide, malnutrition causes approximately 45% of all deaths among children under 5 years of age. The largest number of global incidences of malnutrition is observed in developing countries. In Namibia, 24% of children within this age group are stunted while wasting is at 6.2%, (the highest in Southern Africa). The main causes of malnutrition in Namibia are low education of mothers or caregivers of the children and food insecurity usually correlated to the household income. Therefore, treatment efforts usually include nutrition based interventions that involve providing nutritious foods to malnourished children. Protein rich legumes are often used together with cereals to form composite flours. Tylosema esculentum, (Burchell) Schreiber, commonly known as Marama bean may be used to treat malnourished children due to its high nutritious value. Indigenous to Namibia, Botswana and South Africa, Marama bean seeds have comparably high protein content ranging between 29% and 39% while lipids are between 32% and 42%. The high nutrition value of Marama bean and its physical attributes allow it to be ground into a flour and used in porridge. Marama bean is an appealing crop to Namibia in particular due to its low cultivation demands as it grows in sandy soils with minimal water requirements and no need for fertilisers. Objectives: The aim of this study was to comparatively analyse the nutritional composition of ten Marama bean accessions from the germplasm in Namibia. The objective was to determine the accession most suitable for crop development with the intended use as a biofortifier to provide alternative food sources to malnourished children under the age of 5 years. Results: Marama bean seeds from the ten accessions were dried and analysed using several analytical techniques. Ash content was used to determined overall mineral content by mass using dry ashing via a blast furnace. The amount of ash in all samples ranged between 2.1% and 3.5%. Essential minerals analysed using ICP-OES and photospectrometry were calcium, magnesium and phosphorus. The range of concentrations and p values obtained were 750.11 - 2306.22 mg/kg (p=0.538), 1764.12 - 7415.04 mg/kg (p=0.621) and 4300.81 - 5267.93 mg/kg (p=0.111) respectively. Trace minerals analysed using ICP-OES were iron and zinc. Iron concentration ranged from 53.90 - 322.40 mg/kg and there was no significant difference (p=0.099) between the accessions. Data on zinc concentrations were analysed with non-parametric tests which found the data to be not significantly different (χ2 = 3.073, p = 0.961). The lowest concentration of zinc was 32.2 mg/kg while the highest concentration was 48.8mg/kg. Analysis of the minerals revealed that there was no significant difference in concentration among the ten accessions. Correlation analysis of the minerals within the accessions showed that the distribution of the concentrations of the 5 minerals was similar throughout all accessions. However, pairwise analysis found that the correlations between zinc-magnesium and zinc-phosphorus were significantly different as compared to the rest of the pairs for all accessions. The concentration of crude fatsdetermined using Soxhlet solvent extration (χ2 = 22.934, p = 0.006) and carbohydrates determined by deduction (χ2 = 20.215, p = 0.017) also did not have a significant difference across all accessions. The maximum and minimum amounts observed were 29.93%- 44.06% and 19.41%- 39.04% respectively. Crude protein content was determined using the Dumas combustion method. Protein data had a significant difference (p