Grain and Flour Quality of Ethiopian Sorghum in Respect of their Injera Making

Potential

Senayit Yetneberk, Lloyd W. Rooney, John R. N. Taylor and H.L. de Kock

EIAR UP

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Introduction• Injera is an Ethiopian fermented leavened

flat bread made from various cereal flours

• It is characterized by having “eyes” (honeycomb-like holes) on its top surface

Sorghum injera(TI 76#23)

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Introduction (continue)

• Tef is preferred for the best quality injera for softness and rollability

• Staling is a common problem to almost all baked products from sorghum

• Notwithstanding this, nearly 80% of the sorghum produced in Ethiopia is used for the production of injera (Gebrekidan and GebreHiwot, 1982)

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Objectives 1. To confirm the role of grain quality in

sorghum injera making

2. To determine the sorghum grain physico-chemical factors involved in injera making quality

3. To establish objective indicators for rapid evaluation of sorghum cultivars in terms of injera making quality

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Materials • Twelve sorghum cultivars grown in two growing

seasons at the Melkassa Agricultural Research Center, Ethiopia

• A white tef cultivar DZ-01-196 with excellent injeramaking quality is used for comparison

o These cultivars had differentendosperm texture and pericarp color

o Four cultivars had pigmented testaDO NOT C

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Measured parameters

• Kernel characterization• Flour characterization• Evaluation of injera quality attributes

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Kernel characterization

• Thousand kernel weight (TKW) • Glume color • presence of a pigmented testa • Pericarp thickness • Endosperm texture

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Kernel characterization (continues)

• Grain hardness using o Extraction rate using TADD mill o Endosperm corneousness by image

analysiso Endosperm visual evaluation

• Test weight (hectolitre weight)• Pericarp thickness image analysis

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Flour characterization

• Water solubility index • Water absorption index • Pasting property • Flour gel property

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Evaluation of injera quality attributes • A descriptive sensory analysis for objective

measurements of the attributes of injera

• Instrumental texture analysis of fresh and stored injera

o Over a storage period of 48 hrs using a three-point bending rig attachment

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Endosperm corneousness (image analysis)

o Endosperm texture varied from floury to vitreous

o Vitreous sorghum cultivar had a high extraction rate (89.7%) after abrasive decortication

Germ

Germ

Germ

CR:35:5

PGRC/E 69341

SC-108

Floury

Intermediate

More vitreousDO NOT C

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al

Differences in pericarp thickness (image analysis)

CR:35:5

SC-108

Pericarp thickness ranged from thin to thick

Pericarp thickness affects

o Milling performance

o Flour quality

o Storage property

P

P

P

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-5

0

5

10

15

20

0 5 10 15 20 25 30

Double compression of sorghum and tef flour gel aged for 24 hrs at 4 ▫C sorghum (76 TI#23) ……. and tef (DZ 01 196) ____

o The breaking point of sorghum flour gel was much lower compared to tef flour gel

o Tef flour gel almost returned back to its undeformed condition

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Steps in injera preparation

Fermentation (48 hours)

Gelatinization

Second fermentation (2-3 hrs)

Mixing with water + addition of ersho

Sorghum flour

Baking

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IS-777

AW

Seredo

CR:35:5

3443-2-op SK-82-022

Gambella 1107

PGRC/E #69349

SC-423

SC-108

Tef

-6 -4 -2 0 2 4 6

PC 1: 43.65%

-6

-4

-2

-

0

2

4

6

PC 2: 26.48% 76TI #23

PGRC/E #69441

IS-777

AW

Seredo

CR:35:5

3443-2-op SK-82-022

Gambella 1107

PGRC/E #69349

SC-423

SC-108

Tef

-6 -4 -2 0 2 4 6

PC 1: 43.65%

-6

-4

-2

0

2

4

6

PC 2: 26.48% 76TI #23

PGRC/E #69441

IS-777

AW

Seredo

CR:35:5

3443-2-op SK-82-022

Gambella 1107

PGRC/E #69349

SC-423

SC-108

Tef

-6 -4 -2 0 2 4 6

PC 1: 43.65%

-6

-4

-2

-

0

2

4

6

PC 2: 26.48% 76TI #23

PGRC/E #69441

IS-777

AW

Seredo

CR:35:5

3443-2-op SK-82-022

Gambella 1107

PGRC/E #69349

SC-423

SC-108

Tef

-6 -4 -2 0 2 4 6

PC 1: 43.65%

-6

-4

-2

0

2

4

6

PC 2: 26.48% 76TI #23

PGRC/E #69441

white-bs red-bs

eye size

eye even

gritty

sour-atsweet-at

bitter-at

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

PC 2 : 26.48%

red-ts

bitter

sticky

soursweet

white-ts

eyedis

shin

yflu

ffy

rollablesoft

white-bs red-bs

eye size

eye even

gritty

sour-atsweet-at

bitter-at

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

PC 2 : 26.48%

red-ts

bitter

sticky

soursweet

white-ts

eyedis

shin

yflu

ffy

rollablesoft

white-bs red-bs

eye size

eye even

gritty

sour-atsweet-at

bitter-at

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

PC 2 : 26.48%

red-ts

bitter

sticky

soursweet

white-ts

eyedis

shin

yflu

ffy

rollablesoft

white-bs red-bs

eye size

eye evengritty

sour-atsweet-at

bitter-at

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

PC 2 : 26.48%

red-ts

bitter

sticky

soursweet

white-ts

eyedis

shin

yflu

ffy

rollablesoft

white-bs red-bs

eye size

eye even

gritty

sour-atsweet-at

bitter-at

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

PC 2 : 26.48%

red-ts

bitter

sticky

soursweet

white-ts

eyedis

shin

yflu

ffy

rollablesoft

white-bs red-bs

eye size

eye even

gritty

sour-atsweet-at

bitter-at

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

PC 2 : 26.48%

red-ts

bitter

sticky

soursweet

white-ts

eyedis

shin

yflu

ffy

rollablesoft

white-bs red-bs

eye size

eye even

gritty

sour-atsweet-at

bitter-at

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

PC 2 : 26.48%

red-ts

bitter

sticky

soursweet

white-ts

eyedis

shin

yflu

ffy

rollablesoft

white-bs red-bs

eye size

eye evengritty

sour-atsweet-at

bitter-at

-1.0 -0.5 0.0 0.5 1.0

-1.0

-0.5

0.0

0.5

1.0

PC 2 : 26.48%

red-ts

bitter

sticky

soursweet

white-ts

eyedis

shin

yflu

ffy

rollablesoft

Plot of the first two principal component loading vectors of sensory attributes

Plot of the first two principal component scores of the cultivars

o Principal components (PCs) are orthogonal directions of maximum variance in the original dataDO N

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1hr

24 hr

48 hrPGRC/E #69349

Effects of storage time on maximum force required to bend

injera from sorghum (PGRC/E #69349)

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Tef

3443-2op

76TI #23

AWSK82-022

Effects of cultivars on maximum force required to bend injera

after 48 hrs of storage

Tef injera had a higher score of 8.2 for softness in a sensory evaluation

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Significant correlationsParameter Sensory textural attributes and

correlation coefficients

Maximum force required to bend injera

(texture analysis)

(after 24 hr of storage)

(after 48 hr of storage)

vs

vs

Rollability –0.47*

Softness –0.51*, rollability –0.52*,

grittiness 0.54**

Hardness (TADD) vs Softness –0.70***, rollability –0.66***

Endosperm texture (visual rating) vs Softness 0.59**

Vitreousness (image analysis) vs Softness –0.59**

Test weight (hectoliter weight) vs Softness –0.61**, rollability –0.54**DO NOT C

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Significant correlations (continues)Parameter Sensory textural attributes and

correlation coefficients

RVA parameters

Peak viscosity (flour) vs Stickiness 0.46*

Final viscosity (flour) vs Shininess 0.48*

Setback viscosity (flour) vs Shininess 0.50*

Hot-paste viscosity (flour) vs Stickiness 0.50*

Water solubility index (flour) vs Fluffiness 0.48*

Water absorption index (flour) vs Stickiness 0.45*, fluffiness –0.70***

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Conclusion• Cultivars with floury endosperm, relatively

lower test weight with low extraction rate were positively correlated with soft and rollable sorghum injera texture

• Water solubility index of the flour was positively correlated with fluffiness of injera

• These parameters have potential to be used as indirect indices in predicting the quality of sorghum injera in ESIPDO N

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Proposed selection criteria at early generation stage

Parameter/method Acceptable ranges Remarks

Pigmented testa (Chlorox Bleach Test) Absent These methods require

small sample size and

are predictive tests for

injera making potential

Pericarp color (visual rating) White preferred

Endosperm texture (visual rating) 3-5

Water solubility index (whole flour) ≥2.5 g/100 g

Water absorption index (whole flour) ≤1.5 g/g

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Proposed selection criteria at advanced generation stage

Parameter/method Acceptableranges

Remarks

Hardness (TADD) (extraction rate) 56.0-79.0%The sample size from advanced lines is large enough to prepare the actual product

Test weight (hectolitre weight) 71.0-75.0 kg/hl

Sensory textural attributes of fresh injera

Softness Score of ≥6.7

Stickiness Score of ≤2.0

Fluffiness Score of ≥6.8

Roll ability Score of ≥7.2

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Proposed selection criteria at advanced generation stage

Parameter/method Acceptableranges

Remarks

Grittiness Score of

≤2.7 The sample size from

advanced lines is large

enough to prepare the

actual product

Maximum force required to

bend injera (texture analysis)(after 24 hr of storage) ≤0.27 N

(after 48 hr of storage) ≤0.33 N

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Future research needs• It is required to test a larger number of sorghum

lines, about 15-20 cultivars across 2-3 locations

• Test exclusively soft and hard endosperm sorghum cultivars to more clearly understand the effect of grain endosperm texture

• In-depth study on the structural properties of starch components of the cultivars with high and low staling properties is required

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Acknowledgements

• The South African National Research Foundation for sponsoring me to attend this conference

• The organizing committee for inviting me to present my work

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