The Contribution of flour components to the structure of injera, an Ethiopian fermented bread made from tef (Eragrostis tef)

Abstract

Injera, a pancake-like fermented bread prepared from white or red tef (Eragrostis tef) flour, is the traditional staple food of Ethiopia. The fate of the major components of the bran and endosperm during the two-stage fermentation and baking has been examined by light and electron microscopy. Angular starch granules released from compound grains during milling showed a range of erosion effects typical of enzymic degradation during fermentation. The appearances of bran and embryo fragments, cell walls and protein bodies were unaffected by fermentation or baking. Microorganisms, the natural contaminants of tef grains, produced strands of fibrillar material during fermentation that bound the flour particles together. Apart from the presence of polyphenolic material in the testa cells of red tef, no structural differences were observed between red and white grain during the preparation of injera. The portion of dough that was thinned, boiled and returned to the mixture for the second fermentation period contained swollen gelatinised starch. During cooking, the starch within the injera was totally gelatinised to form a steam-leavened. spongy starch matrix, in which fragments of bran and embryo, micro-organisms and organelles were embedded. The protein bodies played no role in the formation of the matrix-gas bubble interface.