Effect of Different Cereal Blends on the Quality of Injera a Staple Food in the Highlands of Ethiopia

Majority of the Ethiopian population are dependent on tef (Eragrostis tef (Zucc) trotter) flour to make injera, a staple food in Ethiopia, although injera could be made from different cereals. The price of tef, however, is high and the yield potential of the crop is low. Thus, searching for alternative cheaper grains and developing a blend of different cereal flours that can produce injera of acceptable quality and improved nutritional value would be important. This study was conducted to evaluate the sensory quality of injera made from a blend of different cereals (Tef, barley, sorghum and maize) with differing ratios: 100, 75, 50 and 25%. The sensory evaluation of injera was conducted at Mekelle University in a replicated trial. The results revealed significant differences among the cereal flour blends in injera texture, mouth feeling, suppleness and overall rate, while colour, taste and the appearance of injera surface gas holes were nonsignificant. Injera made from 100% tef flour got the highest preference rank in terms of the texture, mouth feeling, suppleness and overall ratings. Injera made from 50:50 tef + barley blend was the second best in both texture and suppleness followed by 50:50 tef + sorghum, 50: 50 tef + maize blends and tef + barley + sorghum blend of equal ratio. Similarly, results from blend of tef + barley + maize, tef + sorgum + maize and from the four varietal blends in equal ratios produced very good injera quality. From the study results injera quality ranked next to sole tef (tef + barley, tef + sorghum, tef + maize in 50:50 blends and tef + barley + sorghum in equal ratios) could be used as an alternative option for injera utilization and could provide nutritional and dietary benefits to consumers.


INTRODUCTION
Agriculture is the main stay of the Ethiopian economy and accounts for 42% of the Gross Domestic Product (GDP) and 84% of the total exports and creates employment for 77% of the total population (ATA, 2015).The population of Ethiopia is increasing at a faster rate (2.5%), and with a population of 94.35 million, it is the second largest population in Africa next to Nigeria (Central Statistical Agency (CSA), 2017a).It is a priority of the government to increase agricultural production and productivity to improve food security of the increasing population.In the year 2016/2017 main crop season, production of cereal grains covers 81.27% of total area under grain crops production (10.2 million ha), with tef (Eragrostis tef ), maize, sorghum, wheat and barley being the major cereals that cover the highest area coverage, respectively of all crops (CSA, 2017b).However, Ethiopia is still facing challenges of food security as observed in the year 2015/2016 drought problem, where around 12 million people from food insecure households were in need of food assistance.Despite Ethiopia's richness in diversity for many cultivated crop varieties; there is a critically concerning issue that the food habits of most Ethiopian population need a change through research.Because majority of the Ethiopian population are dependent on flat bread (injera) made mainly from tef, while there are diverse crop varieties to use.Even the awareness of the consumers both in rural and urban areas on the benefits of diverse food system is very limited.
Although injera could be made from fermented dough of different cereals such as tef, barley, sorghum, wheat and maize, injera from tef is still commonly preferred and daily consumed by majority of the people (Zegeye, 1997;Yetneberk et al., 2004).This is due to its softer texture, preferred taste and colour (Yetneberk et al., 2005;Abraha et al., 2013).Normally, injera with uniformly distributed surface gas holes, soft plumpness, non-sticky and having slightly sweet taste is commonly preferred by injera consumers (Abraha et al., 2013).
Exporting tef grain from Ethiopia is legally restricted due to high consumption demand within the country; however, fresh injera made from tef is being exported to Ethiopian Diaspora in the US, Middle East and Europe (Abraha et al., 2013).This aggravates the price of tef which becomes unaffordable to low income citizens.Thus considering the increased price of tef grain in the local market and its low yield potential, searching for less expensive grains such as barley, sorghum, maize and wheat that can be used in blend with tef has become very important.
Moreover, foods prepared from different cereal blends could provide better nutritional and dietary values for health, besides food security.For instance barley has high beta-glucan and fiber content serving as a functional food.A number of research findings also confirmed that eating of barley foods serves as a healthy food preventing life style diseases such as diabetes, heart diseases and lowers blood cholesterol levels (McIntosh et al., 1995;Tiwari and Cummins, 2011).Similarly, Tef is also considered as a healthy food having high iron content, has slowly digestible starch and glutein free that makes ideal for glutein intolerance people.Compositional analysis and sensory quality evaluation of improved barley varieties in northern Ethiopia indicated that good quality injera comparable to tef could be produced (Abraha et al., 2013).
This implies that barley and other cereals could be used to substitute tef or in combination with tef to make quality injera.Moreover, farmers in Tigray, northern Ethiopia, emphasize different traits such as grain yield, maturity and use value when choosing varieties for production and

Preparation of injera from cereal flour blends
Five kilo grams of quality grains were taken from selected improved varieties of Tef (variety for three days and again thoroughly mixed by adding 350 ml water to each until it reaches a uniform level of dough softness.On the fourth day boiled water (600 ml) was added to the dough, thoroughly mixed and thinned to a uniform level and the injera was baked on an electric clay stove at an average temperature of 170 o C.

Sensory evaluation of injera
Sensory evaluation of injera was conducted at Mekelle University campus by pre-informed on the scale and procedures of sensory taste.The sensory evaluators were six males and six females the upper surface, and suppleness.Each participant was allowed to taste pieces of injera from each blend twice and rate using a scale of 1 to 5 where (1 = very poor, 2 = poor, 3 = good (less acceptable), 4 = very good (acceptable quality), and 5 = excellent, comparable to tef) for a given quality attribute.All sensory evaluations were conducted in two replications and all sensory data were recorded.

Data analysis
All the sensory data were subjected to analysis of variance using GenStat software (14 th edition) (http://www.VSNI.co.uk) and in the model of data analysis varietal blends were considered as fixed and replications as random effects.Treatment mean comparisons were done using Duncan's multiple range tests.Treatment differences were declared at probability P < 0.05 level of significance.Principal component analysis (PCA) was done to study the correlation and relationship in sensory attributes and the different varietal blends using PAST statistical software version 2.17b (Hammer and Harper, 2012).

The analysis of variance model
Y ij is a random variable observation from the i th treatment in j th replication, μ, t i & r j are the general mean, effect of the i th treatment & effect of the j th replication, and e ij is the error component.
Figure 1.Sensory evaluation of Injera made from different cereal flour blends at Mekelle University.

RESULTS AND DISCUSSION
The study has shown significant differences among the different cereal flour blends in sensory quality attributes such as texture, mouth feeling, suppleness and overall rating, while the appearance of surface gas holes, color and taste of injera made from the different cereal flour blends were non-significant at p-value of 5% level.Comparing the sensory preference results has revealed that injera made from sole tef has got the highest average preference scores in texture, mouth feeling, suppleness and overall rate.Injera made from a blend of tef + barley in 50:50 ratio was the second best comparable to tef in texture, mouth feeling and suppleness followed by tef + sorghum, tef + maize in 50:50 blend ratio, and tef + barley + sorghum (ABC) in 33% ratio each (Table 1).Similarly, injera made from the three equal flour blend ratios (33%) of each: tef + barley + maize (ABD), tef + sorghum + maize (ACD) and injera made from all four varietal blends (ABCD) in equal proportions (25%) from each produced acceptable injera quality comparable to the second group ranked as very good (Table 1).On the other hand injera made from sole sorghum, maize, and blend of barley + sorghum, barley + maize and sorghum + maize in 50:50 ratios and a blend from barley + sorghum + maize (BCD) produced a third group ranked as good but was relatively less preferred injera quality for most of the sensory attributes (injera texture, mouth feeling, suppleness, taste, overall rate).Although it was not significantly different, injera made from sorghum, maize, barley + sorghum blend and tef + sorghum + maize had better preference score in injera colour and surface gas holes.From the overall ranking, injera made from sole tef was the best followed by injera made from a blend of tef + barley + sorghum; tef + maize; tef + sorghum + maize, and from the four varietal blends (ABCD) table 1.
Most of the sensory traits showed a significant (P < 0.05) positive correlation (r>0.71) with each other except for injera colour.Injera texture was positively (P < 0.05) correlated with injera mouth feeling, taste, suppleness and overall rate rank, but it was not correlated significantly with surface gas holes and colour.While injera surface gas holes showed a significant positive correlation (p<0.05) with injera taste and overall rate.Although statistically not significant, the preference score for injera colour was higher in sole sorghum, barley + sorghum, tef + sorghum + maize (ACD), and the four varietal blends (ABCD) than sole tef and other blends (Table 1).
Sensory result of the principal component analysis (PCA) revealed that the sensory attributes and preferred injera blends were displayed to the right quadrant of the bi-plot with tef being the leading best preferred, while poor or less preferred injera blends are displayed on the left Injera made from sole sorghum (100%) and sole maize has got the lowest preference scores for most of the quality attributes except for color and surface gas holes.This is clearly displayed in the bi-plot (Fig 2 ) where the flat bread made from maize and sorghum was displayed to the left quadrant indicating less overall preference rate.
From the study injera texture, mouth feeling, suppleness and overall rate were the main determinants for the injera preference and acceptability ranking differences.But the overall sensory quality ranking was less affected by taste, color and surface gas holes differences.This might be because there was less variation in taste, colour and surface gas holes among the different flour blends.Moreover, varieties with different colors such red tef and black seeded barley were not included in the study.
The sensory quality evaluation results has demonstrated that injera made from tef had an excellent preference score as expected, and very good injera quality was also obtained from the other different varietal blends with tef.This implies that injera made from varietal blends could be used as a substitute to tef in the towns with reasonably fair cost and better nutritional value.
While in rural areas farmers have some experience in consuming injera made from two or more different varietal blends, and the blend ratios they used depends on the availability of cereal grains in the households.With the increasing population growth and rising demands to use for quality injera, using available cereals for injera making with tef or other cereals that give consumers preferred acceptable quality from best varietal blends is crucial to achieve food and nutritional security to the subsistence farmers.Considering the importance of injera in the majority of Ethiopians food habit serving as a major source of energy, our sensory evaluation findings could be used and adopted both in rural and urban populations using the available cereal grains even under the existing impact of climate change on crop production in the country.In the present study the quality and acceptability of injera are dependent on the type of varieties used in the experiment because varietal difference could have an impact on injera quality.Other research reports also indicated that the acceptability and quality of injera is affected by the varietal differences as reported by Gebrekidan and Gebrehiwot (1982) who reported poor quality injera with less gas holes was found in some sorghum varieties and indicated that the poor quality injera in sorghum was due to sticky texture, bitter taste, and high tannin content.Zegeye (1997) also reported significant difference in acceptability of injera made from tef, sorghum, baley and maize cultivars.
Study on sensory quality evaluation of injera made from different barley varieties Abraha et al.
(2013) reported that a very good quality injera comparable to tef was produced from improved barley varieties in Tigray, northern Ethiopia.The same report also indicated that sensory quality differences are governed mainly by varietal inherent differences with less impact from environmental factors.Yetneberk et al. (2005) also reported that decortication of sorghum and compositing with tef improved injera quality.In the study of injera made from tef, Parker et al. (1989) reported that tef starch played a major role in the formation of injera surface gas holes.In the current study, the non-significant difference results in injera surface gas holes, colour and taste indicates that preference ranking among the injera evaluators for these traits was more or less similar.This may indicate the effect of these sensory attributes was lower in determination of the overall injera ranking.

CONCLUSION
From the current study the very good injera sensory results obtained from Tef + barley, tef + sorghum, and tef + maize in 50:50 blend, and tef + barley + sorghum (33% each) implies that these varietal blends could be used as substitutes to the sole tef injera both in the urban towns and in the rural communities.Moreover, consumers could be benefited from the use of injera made from these different cereal flour blends due to their enhanced nutritional contents besides the economic advantage due to lower prices compared to that of tef.As a recommendation, results of the current study could be disseminated and up scaled through participatory demonstration trials to wider consumers.This study results were from sensory preference test only, hence further investigation on compositional and starch pasting prosperities may be needed to supplement information on injera sensory quality results.

ACKNOWLEDGMENTS
This work was financed by Mekelle University and IDRC project and the authors would like to thank both Mekelle University and IDRC project for financial support.The authors also thank Mr. Haftu Embaye and Ms. Tsega Gared for their technical assistance during sample preparations in the experiment, and the academic staffs and students of Mekelle University who participated in the sensory evaluation.
Cimama), sorghum (variety Melkam (WSV 387)), barley (variety Fetina) and maize (variety 545 BHQPY).The grains were milled separately and one kilogram of flour was taken from each crop and used for making different blends.The flour blend ratios were: 100, 75, 50 and 25% from each variety (Tef, sorghum, barley and maize) making a 4 x 4 factorial experiment.Thick dough was prepared by adding equal amount (980 ml) of water and thoroughly kneaded by hand for about seven minutes.The dough was left to ferment at ambient room temperature about (20 o C) from students and academic staff members with age range of 22 to 50 years.Two injera samples made from each variety flour blends were arranged on a flat tray (Fig 1) and were evaluated within two hours after baking.Individual evaluators were asked to compare the different blended injera pancakes for taste, mouth feeling, color and texture, size and distribution of gas holes on Volume 9(2):232-241, 2017 © CNCS, Mekelle University 235 ISSN: 2220-184X
The study was carried out to compare a set of different crop varieties (Tef, barley, sorghum and maize) in different combination for injera making quality; and analyze injera sensory quality and consumer acceptance in relation to blend rations of the different cereals.

Table 1 .
quadrant of the bi-plot (Fig 2).The PC1 explained 65.84% of the variation in the sensory quality analysis while PC2 explained only 19.12% of the variation among the different varietal blends.The PCA bi-plot (Fig 2) results also showed a clear relationship on preference for injera quality.Injera sensory evaluation results of the different varietal flour blends.