Influence of milling type on tef injera quality

Abstract

Injera is an Ethiopian flat bread that is mostly made from tef flour. Injera making on an industrial scale holds a significant economic and social interest but requires a thorough study of how the process variables affect the product quality. The aim of this work was to investigate the effects of mill type (hammer, disc, and blade) on injera sensory quality and starch digestibility. The application of software for the determination of injera quality descriptors and its comparison with visual human eye evaluation was also established. Injera made with disc mill flour had higher overall acceptability (6.6) than that obtained from hammer mill (4.2) and blade mill (4.1) flours. The injera made with blade mill flour obtained the lowest rapidly available glucose and rapidly digestible starch. The outcome of introducing software for the determinations of injera number of eyes was found effective; its difference with human eye determination was insignificant.

The effect of mechanical kneading and absit preparation on tef injera quality

“…Before milling, tef grain was cleaned by sifting. The kneading conditions (time/speed) ( Table 1) were used based on preliminary assessment of injera exporters, kneading machine capacity, and other works on bread dough kneading; similarly the ratio of water to fermented dough for absit preparation was based on previous work (Assefa et al, 2018) and traditional practices. Based on the sensory results, Kneading # 1, with shorter kneading time and slower kneading speed, had moderate overall injera acceptability; #5, with moderate kneading time and moderate speed, had the highest injera acceptability; and #9, with longer kneading time and fastest kneading speed, had the lowest injera acceptability; they were selected for starch hydrolysis, flavonoids, total phenolics, phytate and tannins analysis.…”

“…Absit variables Kneading treatment Time (min) Speed (speed) Absit treatment Fermented dough (ml) Water (ml) 1 1 1 1 100 100 2 1 6 2 100 300 3 1 12 3 100 900 4 3 1 4 300 100 5 3 6 5 300 300 6 3 12 6 300 900 7 7 1 7 0 100 8 7 6 8 0 300 9 7 12 9 0 900 appearance, texture and taste. According to Assefa et al (2018), a normal and typical injera is round, soft, spongy and resilient, about 6 mm thick with uniformly spaced honeycomb-like ""eyes"" on the top. The fermentation of injera starts by adding water to tef flour and mixing or kneading it with a starter (backslopped culture) called ersho.…”

“…Once fermentation takes place, part of the fermented batter is gelatinized by cooking to form the absit which is then added back to the fermented batter. This step initiates the "secondary fermentation" (Assefa et al, 2018). Zannini et al (2012) stated that the functionality of absit in the injera can be described as that of hydrocolloids in gluten-free breads, providing the batter with a better gas-holding capacity because of increased viscosity.…”

Teff (Eragrostis tef) processing, utilization and future opportunities: a review

“…Studies on the effect of different milling processes on the resulting flour quality and characteristics are also scarce. Assefa et al (2018) experimented on the resulting qualities of injera bread made from teff flour that was milled using a hammer mill, stone-disk mill and blade mill. They reported that the injera made from the flour from disk mill has the highest overall acceptability.…”

“…This explains why the disk mill is often used for milling teff in Ethiopia. Moreover, the use of disk mill resulted in the smallest flour particle size and high starch damage, while the blade mill resulted in the largest particle size (Assefa et al, 2018). Studies on the adoption of different milling techniques like roller milling and attrition milling may be conducted in the future since the quality of the final product is significantly affected by the method of milling (Kihlberg et al, 2004).…”