Musyoka J. Ndunge¹*, Abong G. Ooko¹ and Muzhingi Tawanda²

¹Food Science, Nutrition and Technology Department of University of Nairobi, P.O Box 29053-00625, Kangemi, Kenya

 ²International Potato Center (CIP), Sub Saharan Africa (SSA) Regional office, old Naivasha road P.O Box 25171-00603, Nairobi, Kenya

*Corresponding author Email: joymusyoka70@yahoo.com Mobile phone: 0719680794

Abstract

Orange Flesh Sweetpotato (OFSP) puree is an ingredient in food processing for example bakery products to improve vitamin A consumption. The puree is highly perishable limiting its use and keeping quality. This study was carried out to determine the effects of chemical preservatives on pathogens in stored OFSP puree. Puree was prepared, dosed with preservative combinations as follows; A-non-supplemented puree, B-0.05% potassium sorbate plus 0.05% sodium benzoate plus 1% citric acid; C-0.1% potassium sorbate plus 0.1% sodium benzoate plus 1% citric acid; D-0.2% potassium sorbate plus 0.2% sodium benzoate plus 1% citric acid; E-1% citric acid. Puree was inoculated with Escherichia coli and Staphylococcus aureus pathogens at inoculum levels of 5.2×10⁹ cfu/ml and 1.53×10⁹cfu/ml respectively before being evaluated during storage for 10 weeks at prevalent room temperature (23-25^oC) and refrigeration temperature of 4⁰C. E.coli and S.aureus counts decreased significantly (p<0.05) in all puree treatments at the storage conditions except for  non-supplemented puree which recorded a less than 1-log increase in counts at room temperature and  a 3-log decrease at refrigeration temperature. Significant count reduction was recorded more in puree at refrigeration as compared to that at room temperature (p<0.05). Packages of puree with only citric acid were found to have expanded after one week of storage and the puree characterized by alcoholic odors. Preservatives at the concentrations used are adequate to destroy pathogenic microorganisms and ensure extensive use of puree. Citric acid alone is not effective in destroying the pathogens.

Keywords: Staphylococcus aureus, Escherichia coli, Potassium sorbate, Sodium benzoate, Citric acid