1. Department of Food Science and Technology, AL Zaiem AL Azhari University, Khartoum North, Khartoum, Sudan.
2. Department of Food Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
3. Corresponding author. Phone: +27 12 4204296. Fax: +27 12 4202839. E-mail: john.taylor@up.ac.za