1. Food Science and Technology Department, College of Agricultural Studies, Sudan University of Science and Technology, Post Office Box 71, Khartoum North, Sudan, Institute for Technical Chemistry and Environmental Chemistry, Friedrich-Schiller University, Lessingstrasse 12, 07743 Jena, Germany, and National Oil Processing Research Institute (NOPRI), University of Gezira, Post Office Box 20, Wad Madani, Sudan