African Journal of Food Science Vol. 4(9), pp. 603 - 607, September 2010

ISSN 1996-0794 ©2010 Academic Journals  

Full Length Research Paper

Effect of irradiation on inoculated Salmonella parathyphi B and the colour of freeze-dried egg yolk   I. W. Ofosu1, F. B. Apea Bah2, A.  Adu-Gyamfi2*, G. M. Ankar-Brewoo1, I. Oduro1, W. O. Ellis1, M. Boakye-Wallace3 and A. Owusu-Marfo3   1Department of Food Science and Technology, College of Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, 2Biotechnology and Nuclear Agriculture Research Institute, Ghana Atomic Energy Commission, Accra, Ghana. 3Department of Biochemistry and Biotechnology, College of Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.   *Corresponding author. E-mail: adugyamfi21@yahoo.com. Tel: +233 20 8115399. Fax: +233 21 402286.    Accepted 20 July, 2010

Abstract

The effect of irradiation on the colour intensity of freeze-dried egg yolk samples (FDEY), from poultry birds given feed containing different concentrations of annatto extract was investigated. Concentrations of 1, 4, 7 and 10 % of annatto extracts were used in the poultry feed formulation and these were compared with feed containing no additive as well as one containing a commercial feed colourant, ‘carophyll yellow’. The FDEY samples coded R₁, R₂, R₃, R₄, C and C_A respectively were inoculated with Salmonella parathyphi B and irradiated at doses of 0, 3 and 5 kGy with γ radiation from a ⁶⁰Co source. Microbial counts and colour intensity were determined after irradiation. Results of the microbiological analysis showed that both 3 and 5 kGy doses were adequate in practically eliminating Salmonella parathyphi B from the samples. However, it was observed from the colour analysis that irradiation at both 3 and 5 kGy doses caused significant (p < 0.0001) deterioration of the colour of the freeze-dried egg yolk samples.

Key words: Irradiation, Salmonella parathyphi B, colour intensity, freeze-dried egg yolk.