African Journal of Food Science Vol. 5(3), pp. 131-137, March 2011 Available online http://www.academicjournals.org/ajfs ISSN 1996-0794 ©2011 Academic Journals Full Length Research Paper All trans-cis β-carotene content of selected sweet potato (Ipomoea batatas (L) Lam) varieties as influenced by different levels of nitrogen fertilizer application A. N. Ukom 1 *, P. C. Ojimelukwe 2 and E. O. Alamu 3 1 Department of Food Science and Technology, Abia State University, Umuahia Campus, Nigeria. 2 Department of Food Science and Technology, Michael Okpara University of Agriculture, Umudike, Nigeria. 3 Crop Utilization Unit, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. Accepted 3 February, 2011 All trans-cis isomers content of sweet potatoes (Ipomoea batatas (L) Lam) as influenced by different levels of nitrogen fertilizer application were determined by high performance liquid chromatography (HPLC). The nitrogen fertilizer treatments were four nitrogen levels of 0 (control), 40, 80, 120 kg N/ha and four varieties of sweet potatoes: White fleshed TIS87/0087 and TIS8164, orange-fleshed, Ex- Igbariam and CIP Tanzania. The study area was Umudike Southeast Nigeria, located at latitude 05°29’N and longitude 07°33E, and at elevation of 122 m above sea levels. Nitrogen fertilizer significantly (P<0.05) increased trans-cis isomers of β-carotene with incremental nitrogen fertilizer application up to 80 kg N/ha. TIS87/0087 and Ex-Igbariam varieties gave the highest trans-cis isomers of β-carotene at 40 to 80 kg N/ha when compared with the control (0 kg N/ha). Nitrogen fertilizer application above 80 kg N/ha did not increase β-carotene yield significantly (P>0.05) for the varieties studied except CIP Tanzania. β-carotene (trans-cis isomers) has the potential to improve vitamin A status among the vulnerable groups in Southeast Nigeria. Sweet potato being a stable crop in Southeast Nigeria can be effectively used as a vehicle for improving the Vitamin A intake in this ecological zone through biofortification with β-carotene. With nitrogen fertilizer increasing sweet potato production in this ecological zone, the evaluation of the trans-cis isomers of β-carotene content was a major objective. Key words: β-carotene, trans-cis isomers, sweet potato varieties, nitrogen fertilizer application. INTRODUCTION Sweet potato (Ipomoea batatas (L) Lam) belongs to the botanical family Convolvulaceae (morning glory family). It is a perennial crop that is usually grown annually. It grows from underground tuberous roots with trailing, twisting stems that can be as long as six meters. This tuber crop provides food to much of the world’s population, occupying the position of the seventh most important food crop in the world by the beginning of the *Corresponding author. E-mail: tony2008gospel@yahoo.com. Tel: +234-8060-9308-23 21st century (Woolfe, 1992). This root crop has a long history of saving lives. It matures fast, rich in nutrients and is often the first crop to be planted after a natural disaster to provide abundant food supply to the population (Food and Culture Encyclopedia, 2003). The bulk of this staple crop is grown and consumed in the tropics (Kochlar, 1981). In Nigeria, sweet potato is an important part of the peoples diet, eaten boiled, fried for breakfast or as sweet potato chips (Aniedu and Oti, 2007). The National Root Crop Research Institute, Umudike, Southeast Nigeria, holds the sweet potato germplasm with over 50 local and CIP improved varieties in Nigeria.