Sweet Potato [Ipomoea batatas (L.) Lam.]

Sweet potato (Ipomoea batatas) is a staple food source for many indigenous populations in Central and South Americas, Ryukyu Island, Africa, the Caribbean, the Maori people, Hawaiians, and Papua New Guineans. Protein contents of sweet potato leaves and roots range from 4.0% to 27.0% and 1.0% to 9.0%, respectively. Sweet potato could be considered as an excellent novel source of natural health-promoting compounds, such as β-carotene and anthocyanins, for the functional food market. Also, the high concentrations of anthocyanin and β-carotene in sweet potato, combined with the high stability of the color extract make it a promising and healthier alternative to synthetic coloring agents in food systems (Bovell-Benjamin, 2007). Starch and fl our processing forms of sweet potatoes can create new economic and employment activities for farmers and rural households, and can add nutritional value to food systems. Repositioning sweet potato production and its potential for value-added products will contribute substantially to utilizing its benefi ts and many uses in human food systems. Multidisciplinary, integrated research and development activities aimed at improving production, storage, postharvest and processing technologies, and quality of sweet potato and its potential value-added products are critical issues, which should be addressed globally. Cardenas et al. (1993) evaluated 440 entries of sweet potato tubers from the International Potato Center for chemical characteristics related to nutritional value. Dry matter range in the group was 15 to 45 gram per 100 gram. The native entries DLP

2393, DLP 1120, DLP 2312, DLP 1908 and the foreign RCB 361F were selected for use in bread manufacture. Their average dry matter and crude protein was 38.5 and 9.2%, respectively. Sweet potato bread was made replacing 30% of wheat fl our with ground sweet potato tubers. This bread had 11.0% crude protein on dry matter basis which is the same for bread made of wheat fl our. There were no differences in organoleptic characteristics or protein quality between sweet potato or full wheat fl our breads. Sporamin, the tuberous root storage protein of the sweet potato, accounts for about 60 to 80% of the total soluble protein of this organ. The amount of sporamin present in other organs is very low, or even not detectable, in the normal fi eld-grown plants. However, the stem of sweet potato plantlets grown axenically on agar medium containing sucrose accumulated large amounts of sporamin (Hattori et al., 1990). Two-dimensional gel electrophoretic profi les of sporamin precursors synthesized in vitro by polyA+ RNA are indistinguishable between tuberous roots of the fi eld-grown plants and stems of the axenically cultured plants, suggesting that an essentially identical set of the members of sporamin multigene family are expressed in these two organs under different growth conditions. The β-carotene-rich orange-fl eshed sweet potato is an excellent source of provitamin A. In many developing countries, sweet potato is a secondary staple food and may play a role in controlling vitamin A defi ciency. The estimated intervention effect for the ratio of 3,4-didehydroretinol to retinol was –0.008, which indicates a greater improvement in vitamin A liver stores in the treatment group than in the control group. The proportions of children with normal vitamin A status in the treatment group tended to increase from 78 to 87% and did not change signifi cantly in the control group. Thus the consumption of orangefl eshed sweet potato improves vitamin A status and can play a signifi cant role in developing countries as a variable long-term food-based strategy for controlling vitamin A defi ciency in children.