Improvement of Shelf Life of ‘Injera’ Using Chemical Preservatives
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Date
2009-06
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Addis Ababa University
Abstract
Injera is staple Ethiopian fermented bread which can be made from different types of cereals,
particularly from tef (Eragrostis tef). About two-third of Ethiopian diet consists of injera and it
accounts for about two-third of the daily protein intake of Ethiopian population. It has a very
high nutritional value, as it is rich in calcium and iron. Unfortunately, injera has a short shelf
life of 3-4 days essentially due to mould spoilage. The use of weak organic acid as
preservatives is allowed in acidic foods, primarily as mould inhibitor. In this study, the
influence of some commonly used chemical preservatives, benzoic acid, sodium benzoate,
potassium sorbate and calcium propionate was investigated by isolation of moulds before and
during its ambient storage for 12 days. The preservatives were added immediately before
baking at the concentration of 0.1% of benzoic acid/ sodium benzoate, 0.2 % of potassium
sorbate, 0.3 % of calcium propionate and 0. 2 % blend of the four (wt/wt) as recommended by
Food and Drug Administration. Three fungal species: Aspergillus niger, Penicillium sp and
Rhizopus sp found to be responsible in injera spoilage. Penicillium and Rhizopus are more
dominant at the temperature of between 16-200c, while Aspergillus niger is more dominant at
higher temperature of between 25-320c. Injera samples had a pH and moisture content of 3.38-
3.45 and 62-65%, respectively. Antimicrobial activities of the preservatives investigated
prolong the shelf life of injera up to12 days. The effectiveness of preservation was ranked as
sodium benzoate>benzoic acid>potassium sorbate>blend >calcium propionate showing that
benzoates and benzoic acid are the most effective. The incorporation of benzoic acid and its
salt while preparing injera at home or in larger scale processing should be practiced so as to
save a significant amount of injera that is lost due to mould spoilage.
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Keywords
Chemical preservatives