Development of High Protein and Vitamin A Flakes from Sweet Potato Roots and Leaves

Sweet potato (Ipomoea batatas) is one of the most important, versatile and unexploited crops in Kenya. The crop is well adapted to smallholder farming systems, inexpensive to produce, relatively drought tolerant and gives high yields even with minimum inputs. Although widely produced in Kenya, sweet potato remains primarily a subsistence crop. Lack of organized marketing, limited consumer interest and low value addition activities are some of the factors that have contributed to low commercialization of the crop. The overall objective of the current study was to investigate the suitability of incorporating sweet potato leaves into the roots to produce nutritious sweet potato flakes with high vitamin A and protein content. Sweet potato roots were cured to increase the endogenous amylase enzyme and then washed and pre-cooked to enable starch hydrolysis to increase sweetness of the flakes and then heated to boiling to enable mashing. Dried sweet potato leaves powder was then added to the mash sweet potato roots at varying percentages and then dried using single drum drier. Addition of sweet potato leaves was found to significantly (p < 0.05) increase protein content from 6.6% protein to 15.40% when the leaves constituted 50% of the flakes. Beta carotene content of the flakes decreased from 7986 μg/100g when no leaves were added to 3979 μg/100g when the leaves constituted 50% of the flakes. The addition of the leaves reduced the overall acceptability. Colour was the most adversely affected while texture was the least affected by the addition of sweet potato leaves. However, all the flakes with up to 30% leaves were acceptable to the panelists with respect to colour, taste, texture and overall acceptability. Incorporating sweet potato leaves into the roots can therefore improve sweet potato protein and hence improve nutrition and value addition of root-based products such as flakes and flour.