Effect of sun- drying on nutrient content of orange fleshed sweet potato tubers in Tanzania

The aim of this study was to assess the impact of traditional processes practiced in Maswa district Tanzania, on nutrient content of orange fleshed sweet potato tubers. The nutrients content was studied in four dried sweet potato varieties (Jewel, Karoti dar, Kabode and Ejumula), subjected to blanching and cooking. Chemical analyses were carried out on orange fleshed sweet potato tubers to establish levels of nutrients in its fresh and processed forms, using official methods of analysis. β-carotene content was also determined by spectrophotometric method, to see how these nutrients were affected by processing and storage. Results were analysed using R-statistical package version 3.1.2 (2014-10-31) software and means were separated using turkey test. The composition of fresh sweet potato tubers were protein 1.9-2.7%, fat 1.1-1.67%, crude fibre 3 - 3.6%, ash 2.77- 4.2%, carbohydrate content 18 - 26.8% and beta carotene 24.2 - 73.9mg/100g on dry matter basis and moisture content 65 - 70.4%. For dried samples, the nutrient composition on dry matter basis were protein 4.89-9.29%, fat 0.56-1.93%, crude fibre 3.19-6.07%, ash 1.95-3.54%, carbohydrate content 72.36-80.33% and beta carotene 8.2- 59.8mg/100g. Retention of beta carotene content of dried chips during storage showed that Matobolwa and blanched solar dried chips had highest retention compared to Michembe after six months of storage. Blanched solar dried should be adopted in the place of Michembe because blanched solar dried chips retain more beta carotene, have longer shelf life and the technology is simple to be implemented by famers.