Sweet Potato Varietal Evaluation Trial for Food Nutritional Values
Aim: The aim of this work was to explore the nutrients, minerals, beta-carotene and total carotenoid contents of five sweet potato varieties viz., Agric orange flesh, Agric white, Red skin, Orange flesh and T.U. purple and present the findings in a language that the average reader can understand. This will help consumers to appreciate what they are feeding their bodies with when they eat the different varieties of sweet potato.
Study Design: The sweet potato vines at six week stage were cut into 1.2 m each and transplanted in parallel lines on the same 1.2 m x 2.6 m bed, spaced about 0.52 m from each other in Dukumah Garden. There were five such beds and vine cuttings transplanted in the same order on each bed. The essence was to provide the same soil and environment so that at harvest, the content of their nutrients, mineral salts and other food factors can be compared.
Study Site: The study, which took four months, was conducted in the Dukumah Garden in Bolgatanga Municipality (10.7875°N, 0.8580°W) of the Upper East Region of Ghana.
Methodology: The sweet potatoes were harvested four months after transplanting on the same day. Samples of the various varieties were collected, parceled, appropriately labelled and hand-delivered to the Food Chemistry Laboratory of Kwame Nkrumah University of Science and Technology for proximate analysis (%), total carotenoids and beta-carotene concentrations in milligrammes per gram (mg/g) and concentrations of the minerals, namely magnesium (Mg), sodium (Na), potassium (K), calcium (Ca), iron (Fe) and zinc (Zn) in milligrammes per kilogramme (mg/kg).
Results: All the five varieties of sweet potato were found to be nutritious. Protein content ranged from 3.82% in the Agric white variety to 0.11% in Agric orange flesh. Fat content ranged from 4.84% in orange flesh variety to 1.74% in red skin. Crude fibre content was between 1.77% in Agric orange flesh and 0.10% in T.U. purple. Total carbohydrate varied from 23.2% in Agric orange flesh variety to 15.8% in Agric white one. Moisture was high in all the varieties, ranging from 75.78% in Agric white variety to 71.04% in Orange flesh one. The Orange flesh variety had the highest ash content of 1.56%. All the varieties contained high concentrations of Mg but low concentrations of Na and K. The highest concentration of Ca (8250.70±0.06 mg/kg) was recorded in T.U. purple. The concentrations of Fe in the sweet potato varieties decreased in the following order: T.U. purple>Red skin>Orange flesh>Agric orange flesh>Agric white. The highest (123.12±0.00 mg/kg) and the lowest (33.10±0.00 mg/kg) Zn concentration were recorded in the orange flesh and Agric white varieties, respectively. The concentration of beta-carotene (mg/kg) in five sweet potato varieties was in the following order: Agric orange flesh<<Agric white<Red skin<Orange flesh<T.U. purple.
Conclusion: The five varieties of sweet potato were found to be rich in proteins, total carbohydrates and fats. They were observed to vary in macro- and micronutrients, beta-carotene and total carotenoids contents. T.U. purple variety was identified to be the richest source of Ca and beta-carotene. Thus, the sweet potato varieties may be of considerable importance in ameliorating nutrient, mineral as well as beta-carotene malnutrition in poorly resourced areas of the developing countries.
For more information contact author
Department of Ecological Agriculture, School of Applied Science and Arts, Bolgatanga Polytechnic, P.O.Box 767, Bolgatanga, Ghana.
Department of Hotel Catering and Institutional Management, School of Applied Science and Arts, Bolgatanga Polytechnic, P.O.Box 767, Bolgatanga, Ghana.
E-mail: [email protected]
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