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Presentation 4: Effects of Acidification and Preservatives on Microbial Growth During Storage of Orange Flesh Sweetpotato Puree

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: Mobile phone: 0719680794



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 (23-25oC) 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

Authors: Joyce Musyoka

Subjects: MPU CoP


Publication Date: 2017

Rights: Attribution 4.0 International (CC BY 4.0) - You can copy, distribute, display and perform the work and evolved versions of it. You must give the original creator credit for the work.

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