Improvement of Injera Shelf Life and Staling Through Vacuum and Non-Vacuum Polyethylene Packaging: Their Synergistic Effect With Chemical Preservative
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Date
2019-03-05
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Addis Ababa University
Abstract
Injera is naturally-leavened fermented sourdough-risen flatbread, indigenous to Ethiopia. It is
commonly made from tef (Eragrostis tef). Injera has nutritional merits, mainly gluten free
protein and high calcium and iron content. Unfortunately, injera has a short shelf life of 3-4 days
basically due to mould spoilage. Its traditional storage condition favors mold spoilage and
quality loss. Use of critical preservation techniques like packaging is ideal for retardation of
mold growth. The application of vacuum packaging (VP) and non-vacuum packaging (NP) of
injera, with or without preservative added (sodium benzoate), has been studied for 15 days with
the aim of determining their effect on the shelf-life and staling of injera. Samples were tested for
microbial load analysis, moisture content (MC), pH, and color āLā value (lightness)
determination, visible mold sign inspection and sensory quality evaluation. Oxygen exclusion of
the packaging methods and antimicrobial activities of preservative used, prolong the storage
duration of injera without visible mold growth to more than 15 days; with VP (vacuum
packaging), VP+ (vacuum packaging with preservative) and NP+ (non-vacuum packaging with
preservative) treatments. Among these, VP+ had least microbial load (5.3*101 & 9.0*101
bacterial & yeast and mold colony forming unit (cfu)/g respectively). But it was least effective
regarding staling as it had least average scoring of MC, pH and L value (60.96%, 3.33 & 45.92
respectively) and sensory acceptability, basically due to crumbling effect of the packaging
method used. Beside, NP+ had lower microbial load (7.5*101 bacterial cfu/g and 9.0*101 yeast
and mold cfu/g). Despite VP and VP+, NP+ was relatively effective method regarding sensory
acceptability and staling as it had 62.73%, 3.32 & 48.70 average MC, pH and L value
respectively. Generally, packaging methods and preservative used found to have a significant
effect (P<0.05) on microbial load, physico- chemical properties and sensory attributes of injera.
Moreover, it was proved that NP+ was the most effective method to improve the shelf life and
staling of injera.
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Keywords
Improvement of Injera, Shelf Life, Staling Through Vacuum, Non-Vacuum, Polyethylene Packaging, Synergistic Effect, Chemical Preservative