Physicochemical characteristics of grain and flour in 13 tef [Eragrostis tef (Zucc.) Trotter] grain varieties

Abstract

In view of the limited information on tef grain and flour quality factors, 13 tef (Eragrostis tef) grain varieties were characterized for grain physical, proximate%, amylose% and flour starch pasting. The grain length (width) were ranged 1.30 (0.67)-0.51 (0.10) [mean = 1.17 (0.59)-0.61 (0.13)] mm, grain mass retained on 600 + 300 microns were about 98% and thousand kernel weight (TKW, g) were between 0.285-0.241 (mean = 0.264). The % proximate compositions are of typical for tef grain reported elsewhere. Both amylose% [25.8-20.0 (23.0)] and amylograph flour starch pasting showed that no waxy-or amylo-type starch traits in the varieties. The pasting temperature (PT) is high, because tef is a tropical C4 cereal. Tef flour starch showed less thickening ability, more shear tolerance and slow setback compared to maize starch. A variety (DZ-01-1285) with least grain protein (GPC) showed highest peak (PV), cold (CPV) and setback (SB) viscosities. The GPC was negatively weak correlated with PV (r = –0.461, p< 0.01), hot paste viscosity (HPV) r = –0.365 (p< 0.05) and break down (BD) (r = –0.360, p< 0.05) as similar reported for wheat flour starch pasting. Negative correlation (p < 0.01) between amylose%: PT (r = -0.606) and pasting time (Pt) (r = -0.460) were observed as with the normal cereal starches. However, in tef flour starch pasting, a subtle increase in the amylose% was weakly correlated toward increase of amylograph setback viscosity (SB, gelation tendencies) in part probably because of interferences of other flour components on the gelation tendency of amylose.

Full text

Journal of Applied Sciences Research, 3(12): 2042-2051, 2007
© 2007, INSInet Publication
Corresponding Author: Geremew Bultosa, Department o f Food Science and Post harvest Technology, Box 22, Haramaya
University Campus, Ethiopia,
E-mail: Bultosageremew@yahoo.com. Fax: 251-025-5530325 or 251-025-5530331
2042
Physicochemical Characteristics of Grain and Flour in 13 Tef
[Eragrostis tef (Zucc.) Trotter] Grain Varieties
Geremew Bultosa
Department of Food Science and Post harvest Technology, Box 22,
Haramaya University Campus, Ethiopia.
Abstract: In view of the limited information on tef grain and flour quality factors, 13 tef (Eragrostis tef)
grain varieties were characterized for grain physical, proximate%, amylose% and flour starch pasting.
The grain length (width) were ranged 1.30 (0.67)-0.51 (0.10) [mean = 1.17 (0.59)-0.61 (0.13)] mm, grain
mass retained on 600 + 300 microns were about 98% and thousand kernel weight (TKW, g) were between
0.285-0.241 (mean = 0.264). The % proximate compositions are of typical for tef grain reported elsewhere.
Both amylose% [25.8-20.0 (23.0)] and amylograph flour starch pasting showed that no waxy- or amylo-
type starch traits in the varieties. The pasting temperature (PT) is high, because tef is a tropical C4 cereal.
Tef flour starch showed less thickening ability, more shear tolerance and slow setback compared to maize
starch. A variety (DZ-01-1285) with least grain protein (GPC) showed highest peak (PV), cold (CPV) and
setback (SB) viscosities. The GPC was negatively weak correlated with PV (r = –0.461, p< 0.01), hot
paste viscosity (HPV) r = –0.365 (p< 0.05) and break down (BD) (r = –0.360, p< 0.05) as similar
reported for wheat flour starch pasting. Negative correlation (p < 0.01) between amylose%: PT (r = -
0.606) and pasting time (Pt) (r = -0.460) were observed as with the normal cereal starches. However, in
tef flour starch pasting, a subtle increase in the amylose% was weakly correlated toward increase of
amylograph setback viscosity (SB, gelation tendencies) in part probably because of interferences of other
flour components on the gelation tendency of amylose.
Key w ords: Amylograph, Amylose, Eragrostis tef, Flour starch pasting, G rain plumpness, Injera,
Proximate composition
INTRODUCTION
Tef [Eragrostis tef (Zucc.) Trotter] is indigenous
cereal crop in Ethiopia with largest share of area
(22.7 %, 2.4 million hectares) under cereal cultivation
and third (i.e. after maize and wheat) in terms of grain
production (16.3 %, 24.4 million quintals) . Tef grain
[12]
flour is widely used in Ethiopia for making injera
(staples for the majority of Ethiopians, a fermented,
pancake-like, soft, sour, circular flatbread), sweet
unleavened bread, local spirit, porridges and soups .
[16,19]
Tef grain commands premium price among other
cereals cultivated in Ethiopia. There is a growing
interest on tef grain utilizations because of nutritional
merits (whole grain), the protein is essentially free of
gluten the type found in wheat (alternative food for
consumers allergenic to wheat glutens) . The grain
[15]
proteins are also presumed easily digestible because
prolamins are very small . Tef grain micronutrient
[5,11,25]
is also apparently high , particularly in iron, a result
[22]
of agronomic practices used in Ethiopia and
fermentation on injera making . Because of this, the
[3,33]
prevalence of iron deficient anemia among tef injera
consumers in Ethiopia is low.
Information on the injera natures , nature of
[27,16]
micro-organisms involved in the tef fermentation for
injera making and changes in the physicochemical
[18,20]
properties with fermentation and on injera
baking are available. Various studies
[26,30,31,32] [35,34]
showed that in its injera making and keeping quality
features, tef grain appeared superior among other cereal
grains. Up to the year 2002, 13 tef grain varieties were
released by the Ethiopian tef improvement program for
production in the different agroecological locations in
Ethiopia . The fundamental physicochemical and
[4]
functional properties of tef starches that predicts the
processing and preservation of tef grain products seems
available for only five tef varieties .
[8,9,10]
Problem: Predictive grain and flour quality factors for
tef grain are limited and there are some complaints
also that tef grain varieties are not the same in their
injera making and keeping quality features (some poor
and some good).

J. Appl. Sci. Res., 3(12): 2042-2051, 2007
2043
Objectives: To assess tef grain and flour characteristics
of the 13 varieties, particularly tef grain plumpness
(sizes, %mass on various test sieves and test weight),
proximate composition, flour starch amylose%, pasting
and correlation among the properties.
MATERIALS AND METHODS
Tef Grain Samples: Thirteen (Table 1) released tef
grain varieties were collected from the harvest of
2004-05 of Debre Zeit tef improvement program
(DZTIP) form the breeder seed (Debre Zeit Agricultural
Research Center, Ethiopia). The grain sample was
manually cleaned by siftings and winnowing to ensure
is free from chaffs, dust and other impurities.
Grain physical characteristics:
Grain Size, % Mass on Test Sieves and Thousand
Kernel Weight (TKW): Grain samples (ca. 500g)
were sieved for 5 min with the help of a test sieve
shaker (Wykeham France Engineering Ltd., England)
through a range of sieves (250, 300, 600, 710 & 1000
microns) connected in tandem. Grain size (length and
width) on each test sieves were determined by digital
caliper (±0.01mm). Grain mass (%) was determined
after measuring the mass retained on each test sieves
on electronic balance (± 1mg). Thousand-kernel weight
was determined on analytical balance (± 0.1mg) after
counting 1000 tef grains by a seed counter (Numigral
II Chopin seed counter, France). The results on grain
size, grain mass% and TKW were reported on 12.5%
moisture basis.
Grain Proximate Composition and Flour Starch
Amylose%:
Proximate Composition: Tef grain samples were
milled by disk attrition mill to whole flour to the
fineness level used traditionally for injera making at
the cottage tef grain-milling house (Dire Dawa,
Ethiopia). The flour was then kept in an air tight
sealed plastic bucket at refrigeration temperature
(ca 5 C) over the analysis duration. Moisture was
O
determined by drying approx. 2.5g flour samples by
air draft drying oven method at 130 C for 1h
O
(AACC Method No 44-15A) . Ash was determined
[1]
after ashing about 3g flour samples in a muffle furnace
at 550 C for over 24 h until ashing was complete
O
(AACC M ethod No 08-01) . Grain protein content
[1]
(GPC) was determined by taking approx. 0.3g flour
sample by micro-Kjeldahl method of nitrogen analysis
(AACC M ethod No 46-11) and urea was used as a
[1]
control in the analysis. %Protein = %N x 6.25. Crude
fat was analyzed after HCl acid (25 + 11) hydrolysis
of about 2g flours sample and extraction of the
released lipids with petroleum ether (16mL x 3)
(AACC M ethod No 30-10) . Crude fiber was
[1]
determined by taking approx. 3g flour samples as the
portion of carbohydrate that resisted dilute sulfuric acid
(1.25%) and dilute alkali (1.25%) digestions followed
by subsequent sieving (75 microns), washing, drying
and ignition (AACC Method No 32-10) .
[1]
Flour Starch Amylose%: Amylose (%) was analysed
colorimetrically by iodine binding with amylose by
taking 30-40 mg flour samples according to Charastil
. Normal maize (Merck UniLAB, code: 587 14 00)
[13]
and tef (DZ-Cr-37) starches of 27.8 and 27.2%
amylose, respectively were used as a control .
[8]
Amylose (%) was determined from the standard (0-
100% amylose of 10% variations) calibration curve.
Data were evaluated on moisture and protein
percentages free basis.
Brabender Amylograph Tef Flour Starch Pasting:
The Amylograph was obtained on 10% flour (db) basis
with Micro Visco-Amylograph (Brabender® OHG
®[7]
2003, Brabender M easurement and Control Systems,
Germany) operated at 250 revmin , held at 30 C for
-1 O
1min, heated to 90 C for 5min. at a rate of 7.5 C per
OO
min., held at 90 C for 5min. and cooled to 50 C at a
OO
rate of 7.5 C per min. From the resulting amylograph
O
pasting curve, temperature at initial viscosity increase
(PT, C), pasting time (Pt, min), peak viscosity (PV,
O
BU), hot paste viscosity (HPV, BU) (minimum
viscosity recorded during holding duration at 90 C),
O
breakdown viscosity (BD, BU) (PV - HPV), cooled
paste viscosity (CPV, BU) (viscosity at the end of
cooling period) and setback viscosity (SBV, BU)
(CPV- HPV) were determined by Micro Visco-
Amylograph software (Windows version 72300,
Brabender M easurement and Control Systems,
®
Germany).
Statistical Analysis: At least three replicate data were
analyzed by one-way analysis of variance (ANOVA),
means were compared at p < 0.05 using DMRT and
Pearson correlation coefficients (r) were calculated
among the properties by using SPSS 10.0.1 statistical
package (SPSS Inc., 1989-1999, Chicago, USA).
RESULTS AND DISCUSSIONS
Grain Size, %Mass on Test Sieves and TK W: Tef
grain sizes are extremely small. The size variations
assessed after passing through test sieves (1000, 710,
600, 300 and 250 microns) showed that virtually no
grain had remained on 1000 micron. The length (L,
mm) and width (W, mm) on the highest (710 micron)
and the least (300 and 250 m icrons) were reported in
this paper (Table 1). T he varieties had grain length

J. Appl. Sci. Res., 3(12): 2042-2051, 2007
2044
Table 1: Grain characteristics (size, mass (%) on test sieves and TKW ) of the 13 released tef varieties
Ma ss (%)#
Variety (C olor)-Relea se year Size# --------------------------------------------------------------------------------------- TK W (g)#
L (W) (mm) 710 microns 600 microns 300 microns 250 microns
DZ-0 1-354 (P ale white)-19 70* 1.29cd (0.67)d -0 .62ab(0 .13)a-d 0.73 ± 0.0 5bc 51.7 5 ± 0.6 8cd 47.48 ± 0.65e 0.05 ± 0 .01a 0.278 ±0.00 3d-f
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-0 1-99 (bro wn)-197 0 1.30d(0 .62)c -0.5 1a(0.12 )a-d 1.31 ± 0.07e 55.64 ± 0.14h 4 2.87 ± 0 .05c 0.0 5 ± 0.0 1a 0.283± 0.003e -f
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-0 1-196 (V ery w hite)-1970 1.17a-c (0.60 )a-c-0.83 (0.41) Ä3.33 ± 0.07i 61.79 ± 0.27j 34.82 ± 0.33a - 0.266±0.006c-e
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-0 1-787 (P ale white)-19 78 1.20 b-d (0.62 )bc -0.93 (0.40) Ä0.47 ± 0.06a 53.96 ± 0.56fg 45.30 ± 0.61d - 0.268±0.009cd
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-Cr-44 (White)-1982 1.14ab(0.56)a -0.66b(0.10)a 0.81 ± 0.10c 59.70 ± 1.13i 39.22 ± 1.09b 0.11 ± 0.01a 0.241±0.003a
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-Cr-82 (White)-1982 1.10ab(0.57)ab -0.64ab(0.14)cd 1.58 ± 0.10f 45.98 ± 0.90a 52.24 ± 0.94g 0.59 ± 0.81b 0.260±0.006bc
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-Cr-37 (White)-1984 1.17a-c (0.56)ab-0.65ab(0.15)d 1.83 ± 0.03g 54.60 ± 1.00gh 43.44 ± 1.00c 0.05 ± 0.01a 0.261±0.008bc
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-Cr-255 (White)-1993 1.13ab(0.60)a-c -0.68b(0.15)d 1.12 ± 0.05d 52.73 ± 0.57de 45.98 ± 0.64d 0.10 ± 0.01a 0.252±0.009ab
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-974 (White)-1995 1.11ab(0.58)a-c -0.60ab(0.14)cd 0.56 ± 0.04a 48.90 ± 0.21b 50.42 ± 0.26f 0.06 ± 0.01a 0.253±0.008ab
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-C r-358 (W hite)-199 5 1.16 a-c(0.57 )a-c -0.54a b(0.14)b -d 1.72 ± 0.25 fg 53.04 ± 0 .67ef 45.1 5 ± 0.90 d 0 .08 ± 0 .06a 0.269 ±0.00 3c-e
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-1281 (White)-2002 1.12ab(0.59)a-c -0.68b(0.15)cd 2.88 ± 0.09h 53.17 ± 0.29ef 43.70 ± 0.23c 0.17 ± 0.01a 0.262±0.005bc
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-1285 (White)-2002 1.05a(0.58)a-c -0.58ab(0.12)a-c 0.59 ± 0.06ab 51.51 ± 0.77c 47.67 ± 0.70e 0.18 ± 0.01a 0.250±0.003ab
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-1681 (Dark brown)-2002 1.23b-d(0.59)a-c -0.58ab(0.11)ab 1.36 ± 0.03e 51.34 ± 0.19c 47.13 ± 0.17e 0.07 ± 0.01a 0.285±0.020f
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Mean 1.17 (0.59) -0.61(0.13) 1.12 ± 0.05 52.73 ± 0.57 45.34 ± 5.5 0.12 ± 0.23 0.264 ± 0.010
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Range 1.30(0.67) -0.51(0.10) 3.33-0.47 61.79- 45.98 52.24-34.82 0.01-0.59 0.241-0.285
*Persona l communication from tef improvement program of the DZARC & B elay et al. (2005). #Values within the same column with different letters are
significantly different (p < 0.05) and are means of at least 3 determinations. Grain length (L) and width (W) are values on maximum (710) and minimum (250)
microns sieve ; Ä is value on 300 microns sieve ; TKW is thousand kernel w eight.
(width) ranged 1.30 (0.67)-0.51 (0.10) with mean of
1.17 (0.59) -0.61 (0.13). In earlier works, lengths (mm)
were reported to be ranged: 1.7-0.9 (width = 1.0-0.7
mm) . However, Umeta & Parker had noted
[17] [32]
length to be 1.2-1.0 mm. Also the DZTIP tef breeding
recent progress report had classified tef sieve-size
grades on 350, 425, 500, 600 and 710 microns ,
[29]
which is familiar to this finding. On 710 micron, the
highest grain length was for DZ-01-99 and the least
was for DZ-01-1285. In tef grain varieties DZ-01-196
and DZ-01-787 no thoroughs on 300 micron were
recorded. The % tef grain mass retained on 710 micron
test sieve was small (3.33-0.47) with mean 1.12 ± 0.05
and the highest %mass was recorded for DZ-01-196
and the least was for DZ-01-787 and DZ-01-974
(p< 0.05). The %mass on 600 micron had ranged
61.79-45.98 with mean 52.73. Tef grain DZ-01-196 is
most preferred for market because of its grain size and
white color and the highest %mass on 600 micron
[4,29]
was observed in this variety and the least was for
DZ-Cr-82. On 300 micron, the % mass retained had
ranged 52.24-34.82 with mean 45.34; the highest
was for DZ-Cr-82 and the least was for DZ-01-196.
The mean grain mass retained on 600 + 300 microns
was about 98%. The mass that had passed through 300
microns and retained on 250 microns were very small
(0.59-0.01%).
The TKW for the varieties had ranged 0.285-
0.241g with mean 0 .264g, which is in the range
(0.42-0.19 g) reviewed for tef grain in . The highest
[2]
TKW was observed among DZ-01-354, DZ-01-99 and
DZ-01-1681 and the least was among DZ-Cr-44, DZ-
Cr-255, DZ-01-974 and DZ-01-1285 (p< 0.05). On the
preliminary report of Tefera & Sorrells , with an
[29]
increase in the grain size an increase in TKW and
grain yield was the trend. On this basis and the report
in probably size among tef grain populations few
[17]
might be larger than this finding or in part might be a
manifestation of the moisture level variations.
Grain Proximate Composition and Flour Starch
Amylose%: The proximate composition and amylose%
of the 13 released tef grain varieties are given in
Table 2. The moisture had ranged 11.22-9.30% with
mean 10.53% , which is in the no rmal range for field
dried tef grain . The grain protein (GP) of the
[11]
varieties are ranged 11.1-8.7% with mean 10.4%.
The GP in DZ-01-354, DZ-01-99, DZ-01-787,
DZ-Cr-44, DZ-Cr-82, DZ-Cr-37, DZ-Cr-255 and
DZ-01-1281 was the highest; and in DZ-01-1285
was the lowest (p < 0.05). The GP for tef varieties
were reviewed to range 13-9% with mean 11 % .
[11]
Belay et al. had reported for these 13 released tef
[4]
varieties in the range of 12.4-8.7% with mean 11.0%
and the highest was for DZ-01-99 and the least
was as for this finding (i.e. DZ-01-1285). The ash
content had ranged 3.16-1.99% with mean of 2.45%.
Ash in the brown tef varieties (DZ-01-99 = 3.16% and

J. Appl. Sci. Res., 3(12): 2042-2051, 2007
2045
Table 2: Proximate composition and flour starch amylose % of the 13 tef grain varieties
Variety Moisture (% ) Grain protein (% )& Ash (% )& Crude fat (%)& Crude fibre (%)& Am ylose (%) from flour&
DZ-01-354 11.07± 0.02hi* 10.6 ± 0.7c-f 2.18 ± 0.0b 2.1 ± 0.2a 3.3 ± 0.2c-e 25.8 ± 0.7d
----------------------------------------------------------------- ---------- ---------- --------------------------------------------------------------------------------------------------
DZ-01-99 10.83± 0.13fg 10.8 ± 0.3d-f 3.16 ± 0.0f 2.1 ± 0.0a 3.8 ± 0.3e 22.9 ± 1.2bc
--------------------- ---------- ---------- ---------------------- ------------------------------------------------------------------------------------------------------------------------
DZ-01-196 9.69± 0.03b 10.4 ± 0.6b-e 2.14 ± 0.0b 2.4 ± 0.7ab 3.2 ± 0.2bc 22.1 ± 1.0bc
------- ------- -------------- ------- --------------------------------------------------------------------------------------------------------------------------------------- ------- ------
DZ-01-787 10.85± 0 .12fg 10.4 ± 0.5c-f 2.06 ± 0.0a 2.5 ± 0.5ab 3.5 ± 0.1c-e 23.8 ± 2.1cd
-------------------------------------------------------------------------------------------------------------------------------------- ------- -------------- ------- -------- ------- ------
DZ-Cr-44 9.30± 0.04a 10.7 ± 0.0c-f 2.82 ± 0.1d 2.6 ± 0.6ab 2.7 ± 0.1ab 25.6 ± 0.3d
---------------------------------------------------------------------------------------------------------------------------- ---------- ---------- ---------------------------------------
DZ-Cr-82 10.79 ± 0.14f 10.6 ± 0.3c-f 2.15 ± 0.0b 3.0 ± 0.4b 3.5 ± 0.2c-e 22.3 ± 1.6bc
-------------------------------------------------------------------------------- ---------- ---------------------- ---------- -------------------------------------------------------------
DZ-Cr-37 11.15± 0.08i 11.0 ± 0.2ef 2.54 ± 0.0c 2.0 ± 0.3a 3.3 ± 0.4cd 22.7 ± 0.6bc
---------------------------------------------------------- ---------- ---------------------- ---------------------------------------------------------------------------------------------
DZ-Cr-255 10.24± 0.08d 11.1 ± 0.1ef 3.10± 0.1f 2.5 ± 0.6ab 2.6 ± 0.2a 20.0 ± 0.4a
------------------------------------ ---------- -----------------------------------------------------------------------------------------------------------------------------------------
DZ-01-974 10.33± 0.10d 10.0 ± 0.5bc 2.16 ± 0.0b 2.1 ± 0.2a 3.5 ± 0.3c-e 22.7 ± 0.6bc
------- ------- -------------- ------- --------------------------------------------------------------------------------------------------------------------------------------------- -------
DZ-Cr-358 10.49 ± 0.06e 10.1 ± 0.2b-d 1.99 ± 0.0a 2.2 ± 0.0ab 3.5 ± 0.4c-e 22.4 ± 0.5bc
------- ------------------------------------------------------------------------------------------------------------------------------------- ------- -------- ------- -------------- -------
DZ-01-1281 11.22± 0.11i 11.1 ± 0.2f 2.52 ± 0.0c 2.5 ± 0.7ab 3.4 ± 0.5c-e 22.7 ± 1.4bc
--------------------------------------------------------------------------------------------------------------------- ---------- ---------------------- ---------- ------------------------
DZ-01-1285 9.96 ± 0.06c 8.7 ± 0.1a 2.02 ± 0.0a 2.5 ± 0.6ab 3.1 ± 0.4bc 24.2 ± 2.1cd
------------------------------------------------------------------------------------- ---------- ---------------------- ---------- --------------------------------------------------------
DZ-01-1681 10.96± 0 .04gh 9.7 ± 0.3b 2.99 ± 0.0e 2.0 ± 0.0a 3.7 ± 0.1de 21.2 ± 0.5ab
------------------------------------------------------------------------- ---------- ---------- ------------------------------------------------------------------------------------------
Mean 10.53 ± 0 .58 10.4 ± 0.7 2.45 ± 0 .42 2.3 ± 0.5 3 .3 ± 0.4 23.0 ± 1 .8
----------------------------- ---------------------- ---------- --------------------------------------------------------------------------------------------------------------------------
Range 11.22-9.3 0 11.1-8.7 3.16-1.99 3.0-2.0 3.8-2.6 25.8-20 .0
------- ------- -------------- ------- --------------------------------------------------------------------------------------------------------------------------------------------- -------
Maize s tarch (n=7) 28.4 ± 2 .0
------- ------------------------------------------------------------------------------------------------------------------------------------- ------- --------------------- -------- -------
Tef (D Z-Cr-37) starc h (n=7) 27.7 ± 1 .9
*Values within the same column with different letters are significantly different (p < 0.05) and are means of at least three determinations.
Values are on dry m atter basis
&
DZ-01-1681 = 2.99%) and in DZ-Cr-255 was
comparatively high and in tef varieties DZ-01-787, DZ-
Cr-358 and DZ-01-1285 appeared lowest (p < 0.05). A
review report of the ash level in tef grain had ranged
3.00-2.66% with typical value 2.8% . Apart from the
[11]
genetics, the ash levels in tef grain are influenced by
the agronomic practices used (i.e., by the degree of tef
grain unseen surface contamination mostly from the
threshing floor) . Tef grain used in this study were
[3]
from breeders and comparatively clean than purchased
from the market, hence the slightly less ash level
observed in this study are probably related to this
scenario. The crude fat had ranged 3.0-2.0% with mean
of 2.3% and the value is similar with the review report
of 3.09-2.00% of previous works . The highest crude
[11]
fat was for DZ-Cr-82 and the lowest was among DZ-
01-354, DZ-01-99, DZ-Cr-37, DZ-01-974 and DZ-01-
1681 (p < 0.05). Eventhough, germ in tef is known to
occupy large proportion as in other small grain its
crude fat is known to be not as such high. The crude
fiber (CF) had ranged 3.8-2.6% with mean 3.3%.
Apparently the crude fiber observed in these 13
varieties are almost similar with the earlier report of
3.5-2.0% with typical value 3.0% . The CF was high
[11]
among tef varieties DZ-01-354, DZ-01-787, DZ-Cr-82,
DZ-01-974, DZ-Cr-358 and DZ-01-1281 and was
highest in brown tef varieties (DZ-01-99 = 3.8% and
DZ-01-1681 = 3.7%) (p < 0.05). The CF for DZ-Cr-44
and DZ-Cr-255 were the lowest. Tef is consumed as a
whole grain, bran and cell wall materials were reported
not affected as such on tef fermentation on injera
making . The CF comprises materials that had
[26]
resisted digestions (dilute acid and base). These are
presumably major contributor for the dietary fiber of
characteristic large sto ols bulk on tef injera
consumption.
The tef flour starch amylose% had ranged 25.8-
20.0% with mean 23.0%. Amylose in maize and tef
(DZ-Cr-37) starches analyzed along with the tef flour
varieties were 28.4% and 27.7% , respectively.
The amylose% in four tef starch varieties (DZ-01-99,
DZ-01-196, DZ-Cr-37 and DZ-01-1681), which their
flour included in this work were reported to range
28.8-27.2% . The lower % amylose observed in tef
[8]
flour than in tef starch of the same variety is because
other trace flour components in the flour sample
somehow slightly interferes and suppresses the starch
sample dissolution and the iodine binding with amylose

J. Appl. Sci. Res., 3(12): 2042-2051, 2007
2046
of the blue color formation similar as reported in other
cereals . In addition, ash, fat and fiber contributions
[13,21]
to the total mass% sampled were also not precluded.
Among the tef flours the highest amylose% was for
DZ-01-354, DZ-01-787, DZ-Cr-44 and DZ-01-1285
and the lowest were for DZ-Cr-255 and DZ-01-1681
(p < 0.05). The starch in these 13 tef varieties
appeared normal type and no amylo- or waxy- starches
were observed and the flour starch pasting also support
this (Table 3, Figure 1). In tef grain food products, like
in tef porridges (marqaa), unfermented tef breads
(bixxille), pancakes, biscuits, soups and cookies, all
these tef grain varieties would be expected to have a
normal short stiff paste texture that would slightly vary
from each other probably by the influence of the
narrow range amylose% variations.
Brabender Amylograph Tef Flour Starch Pasting:
The pasting character predicts the processing qualities
(cooking temperature and time, thickening ability,
temperature-pressure-shear induced viscosity
breakdowns, gelling and retrogradation tendencies over
the storage durations) of starch based raw material food
ingredients. The pasting character is fundamentally
determined by the starch granule composition and its
nature (ultra-structures) and is also influenced by the
non-starch flour components. The pasting data and
pasting curves for the 13 tef grain flour starch varieties
are shown in Table 3 and Figure 1, respectively.
The pasting temperature (PT, C) (approx.
O
gelatinization temperature) had ranged 75.9- 67.7 with
mean 72.7. The pasting temperature is high because tef
is a C4 tropical cereal grain. The P T found in this
work is somehow similar to the reported RVA pasting
temperatures (74.8 -72.1 C) for five tef starches and
O [8]
to the starch gelatinization temperatures (64-82 C =
O
DSC method and 68-80 C = Kofler hot stage
O
method) . The highest PT was for tef varieties DZ-Cr-
[9]
82 and DZ-01-1681 and the lowest was for DZ-Cr-44
(p< 0.05).
The TKW of the varieties (Table 4) were
positively correlated with PT (r = 0.457, p< 0.01) and
pasting time, pt (r = 0.370, p< 0.05) but negatively to
the BD (r = -0.352, p< 0.05). The PT was reported
high for high amylose and vice versa among normal
starches . In this work also significant (p < 0.01)
[14]
negative correlation between amylose and PT (r = -
0.606) and between amylose and pasting time (Pt, r =
-0.460) were observed. The highest PT for DZ-Cr-82
and DZ-01-1681 (among low amylose %) and the least
for DZ-Cr-44 (among high amylose %) are most
probably related to this. The pasting time (Pt, min)
(cooking time) were ranged 6.1-5.2 with mean 5.6. The
lowest Pt was among DZ-01-354, DZ-Cr-44, DZ-01-
974 and D Z-01-1285 and the highest was for DZ-Cr-
82, DZ-01-1281 and DZ-01-1681 (p < 0.05). The
varieties Pt was slightly higher than the RVA Pt
reported (5.10-3.43 min) for five tef starches .
[8]
The peak viscosity (PV, BU) had ranged 191.3-
126.0 with mean of 158.0. The highest PV was for
DZ-01-354 and DZ-01-1285 and the lowest was for
DZ-Cr-82. The PV indicates the thickening ability and
water holding capacity of the pasted flour and reflects
the eating quality of the food products to be made.
The PV in wheat was reported be influenced positively
by the prime starch level primarily and to a lesser
extent negatively by the protein level (i.e., due to
competition for water p er se on starch gelatinization) in
sound wheat . A reduced starch amylose in the starch
[23]
granule, due to the genetic related decrease in the
granule-bound starch synthase enzyme (GBSS: ADP
glucose starch glycosyl transferase EC: 2.4.4.21) was
correlated to high PV , eventhough in some work
[36] [24]
not unequivocally observed (i.e., high amylose of high
PV) for wheat starch pasting. In rice with reduced
amylose high PV was reported for varieties of wide
amylose range (28.2-6.3%) . In sorghum also high PV
[28]
was correlated with reduced amylose . In this work,
[6]
a significant positive correlation (r = 0.588, p< 0.01)
was observed between flour starch amylose and the
flour PV. It seems in normal tef (no amylo- and waxy-)
flour starch amylograph pasting, high PV is contributed
by other tef starch characters and other flour
components, but not by subtle reduced starch granule
amylose, since with narrow amylose variation (5.8%)
tef is behaving high PV with high amylose. The GPC
was negatively correlated with PV (r = –0.461, p<
0.01), HPV (r = –0.365, p< 0.05) and BD (r = –0.360,
p< 0.05) similar as reported for wheat by .
[23]
The minimum viscosity (HPV, BU) recorded
during the high temperature (90 C) of 5 min. holding
O
duration had ranged 157.0-115.0 with mean 134.0. The
HPV (holding strength) is the minimum apparent
viscosity recorded upon continuous shear thinning of
the gelatinised system at high temperature for defined
duration and reflects the degree of the disintegration of
the swollen systems and alignments of amylose and
other linear flour components in the direction of the
shear. The HPV is positively significantly (p < 0.01)
correlated with PV (r = 0.814) and CPV (r = 0.772),
whereas the correlation to amylose was positive but not
significant. The highest HPV viscosity was observed
for DZ-01-354 and DZ-01-1285, which have high PV.
The least HPV was observed in DZ-Cr-44 and DZ-Cr-
82 (p < 0.05). Breakdown viscosity (BD, BU) had
ranged 48.0-10.5 with mean of 24.0. The highest shear
stabilities (lowest BD) were observed among DZ-01-
196, DZ-Cr-82 and DZ-Cr-255 followed by DZ-Cr-
37, DZ-01-1281 and DZ-01-1681. The least (highest
BD) was for DZ-Cr-44 followed by DZ-01-1285,

J. Appl. Sci. Res., 3(12): 2042-2051, 2007
2047
Table 3: Pasting properties of 13 tef grain flour varieties
Variety PT ( C) Pt (min) PV (BU) HPV (BU) BD (BU) CPV (BU) SB (BU)
O
DZ-01-354 71.0 ± 0.0bc 5.4 ± 0.0a-c 189.0 ± 4.6g 157.0 ± 3.5f 32.0 ± 1.7e 246.3 ± 1.5e 89.3 ± 2.1ab
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-99 73.7 ± 0.1g 5.7 ± 0.3de 148.0 ± 1.0c 125.7 ± 1.5b 22.3 ± 0.6c 232.7 ± 4.6cd 107.0 ± 3.6c
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-196 72.6 ± 0.4f 5.4 ± 0.0bc 142.7 ± 2.5bc 129.3 ± 3.5bc 13.1 ± 1.2ab 213.0 ± 4.6ab 83.7 ± 1.2a
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-787 71.6 ± 0.0de 5.4 ± 0.0bc 165.5 ± 2.1e 136.0 ± 2.6d 29.5 ± 2.1de 222.5 ± 0.7bc 86.5 ± 0.7ab
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-Cr-44 67.7 ± 0.3a 5.2 ± 0.1a 163.0 ± 3.5de 115.0 ± 4.0a 48.0 ± 2.0g 203.3 ± 3.8a 88.3 ± 2.5ab
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-Cr-82 75.7 ± 0.5J 6.1 ± 0.0f 126.0 ± 2.0a 115.3 ± 1.5a 10.7 ± 2.1a 204.7 ± 17.2a 89.3 ± 15.7ab
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-Cr-37 74.6 ± 0.4h 5.9 ± 0.3e 158.7 ± 7.6d 143.0 ± 6.6e 15.7 ± 1.2b 255.3 ± 9.5e 112.3 ± 3.2cd
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-Cr-255 73.5 ± 0.6g 5.5 ± 0.0cd 137.5 ± 0.7b 127.0 ± 1.4b 10.5 ± 0.7a 227.0 ± 1.4bc 100.0 ± 0.0bc
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-974 71.2 ± 0.1cd 5.4 ± 0.0a-c 173.0 ± 2.6f 143.7 ± 1.2e 29.3 ± 1.5de 243.3 ± 2.1de 99.7 ± 1.5bc
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-Cr-358 71.8 ± 0.1e 5.4 ± 0.0bc 162.0 ± 3.6de 134.0 ± 2.6cd 28.0 ± 1.7d 225.7 ± 7.6bc 91.7 ± 5.5ab
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-1281 75.1 ± 0.1i 6.1 ± 0.0f 147.0 ± 3.5c 131.0 ± 4.6b-d 16.0± 1.7b 252.3 ± 11.7e 121.3 ± 15.9de
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-1285 70.6 ± 0.2b 5.3 ± 0.0ab 191.3 ± 2.9g 152.7 ± 1.2f 38.7 ± 2.5f 284.3 ± 2.5f 131.7 ± 3.5e
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-01-1681 75.9 ± 0.2J 6.1 ± 0.0f 146.0 ± 1.7c 130.7 ± 1.2b-d 15.3 ± 0.6b 216.0 ± 2.0ab 85.3 ± 3.1a
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Me an (Tef flour) 72.7 ± 2.4 5.6 ± 0.3 158.0 ± 19.1 134 .0 ± 12.9 2 4.0 ± 1 1.4 233.2 ± 23.7 99.2 ± 16 .0
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Range (Tef flour) 75 .9-67.7 6.1-5.2 191.3 -126.0 157.0-1 15.0 48.0-10 .5 284.3-2 03.3 131 .7-83.7
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DZ-0 1-99 starc h 70.5 ± 0.4 5.6 ± 0 .0 29 0.0 ± 1 .4 2 50.0 ± 2.8 40.0 ± 1.4 292.0 ± 1.4 42.0 ± 1.4
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Ma ize starch 72 .5 ± 0.4 6.0 ± 0.1 418.0 ± 2.8 324.0 ± 1 .4 9 4.0 ± 1.4 413.5 ± 2.1 89.5 ± 0.7
*Values within the same column with different letters are significantly different (p < 0.05) and are means of at least 3 determinations. Where : PT = pasting
temperature, Pt = pasting time (cooking time), PV = peak viscosity, HPV = hot paste viscosity, BD = Break down viscosity, C PV = cold paste viscosity and SB
= set ba ck viscosity.
Fig. 1: Amylograph pasting curves for starches (s) (maize and DZ-01-99) and 13 tef flour (f) starch varieties
DZ-01-354, DZ-01-787 and DZ-01-974. The BD
measures the differences between PV and HPV
achieved during the high temperature (90 C for 5 min)
O
holding duration and shows the relative differences of
shear thinning and degree of disintegration of the
swollen systems. Tef starch and its flour starch pasting
are shear tolerant and thus had a potential for use in
foods processed under high shear conditions. The BD
was significantly (p< 0.01) correlated positively with
amylose (r = 0.667) and PV (r = 0.755) and negatively
with TKW (r = -0.352, p< 0.05), GPC (r = -0.360, p<
0.05), PT (r = -0.900, p< 0.01) and Pt (r = -0.743, p<
0.01).
The cold paste viscosity (CPV, BU) had ranged
284.3-203.3 with mean 233.2. The highest CPV was
for DZ-01-1285 and the least was for DZ-01-196, DZ-
Cr-44, DZ-Cr-82 and DZ-01-1681. T he CP V is
significantly (p< 0.01) correlated positively with PV
(r = 0.630), HPV (r = 0.772) and SB (r = 0.860).
The SB (BU) had ranged 131.7-83.7 with mean 99.2.
The highest SB was for DZ-01-1281 and DZ-01-1285
and the least was among DZ-01-354, DZ-01-196, DZ-
01-787, DZ-Cr-44, DZ-Cr-82, DZ-Cr-358 and DZ-01-
1681 (p< 0.05). T he CPV and SB predict the degree of
gelation and the gradual reterogradation tendencies on
cooling and storage of the flour starch pasted system.

J. Appl. Sci. Res., 3(12): 2042-2051, 2007
2048
Table 4: P earson correlation coeff icients amon g the gra in and flour qu ality factors in tef grain
Property TKW GPC Ash Fat Fibre Amylose PT Pt PV HPV BD CPV SB
TKW 1.000
-------------------------------------------------------- ---------- ---------------------- ---------- -------------------------------------------------------------------------------------
GPC .008 1.000
-------------------------------- ---------- ---------- ---------------------- -------------------------------------------------------------------------------------------------------------
Ash .116 .376* 1.000
------- ------- -------------- ------- -------- ------- -------------------------------------------------------------------------------------------------------------------------------------
Fat -.404* .110 -.044 1.000
------- ------- -------------- -------------------------------------------------------------------------------------------------------------------------------------- -------------- -------
Fibre .577** -.146 -.100 -.099 1.000
------- ------------------------------------------------------------------------------------------------------------------------------------- ------- -------- ------- -------------- -------
Amylose -.095 -.099 -.287 .029 -.084 1.000
----------------------------------------------------------------------------------------------------------------------------------------- ---------- ---------- --------------------------
PT .457** .230 .249 -.129 .457** -.606** 1.000
------------------------------------------------------------------------------------------------------- ---------- ---------- ------------------------------------------------------------
Pt .370* .260 .303 -.081 .464** -.460** .917** 1.000
----------------------------------------------------------------------------- ---------------------- ---------- --------------------------------------------------------------------------
PV -.136 -.461** -.398* -.203 -.101 .588** -.665** -.653** 1.000
----------------------------------------------------------------- ---------- ---------- --------------------------------------------------------------------------------------------------
HPV .110 -.365* -.435** -.330* .086 .281 -.188 -.310 .814** 1.000
----------------------------- ---------------------- ---------- --------------------------------------------------------------------------------------------------------------------------
BD -.352* -.360* -.175 .033 -.266 .667** -.900** -.743** .755** .234 1.000
------- ------- -------------- ------- -------- ------------------------------------------------------------------------------------------------------------------------------------- -------
CPV -.131 -.294 -.233 .-.287 .013 .195 -.062 -.121 .630** .772** .183 1.000
------- ------- --------------------------------------------------------------------------------------------------------------------------------------------- ------- -------- ------- ------
SB -.285 -.139 .004 -.157 -.051 .061 .060 .070 .278 .340* .082 .860** 1.000
Where: TKW is thousand kernel weight; GPC is grain protein content; PT is the pasting temperature; Pt is the pasting time; PV is the peak
viscosity; HPV is hot paste viscosity; BD is breakdown viscosity; CPV is cold paste viscosity and SB is setback viscosity. *Significant at p<
0.05 and **significant at p < 0.01
Tef starch was known to have less thickening ability,
shear tolerance and slow setback than commercial
normal maize starch on the RVA pasting and similar
[8]
is also seen in the Brabender amylograph pasting
(Table 3 and Figure 1). Tef starches were also known
to have slow reterogradation tendencies on the
refrigeration and freeze storages and freeze-thaw cycle
treatments than the maize starches . The correlation
[10]
of CPV and SB with amylose in tef flour starch
pasting was positive but insignificant, because in part
gelation tendency of amylose is suppressed by other
flour components. In addition to the known tef starches
slow starch reterogradation tendencies, probably such
weak SB (gelation tendencies) in the flour is also in
part a contributor for tef injera good keeping qualities
than injera made from other cereal flours.
Conclusions: Quality factors in tef grain and flour for
injera making are not clearly addressed to this date.
Traditionally: plump (non-shriveled), clean and non-
sprout damaged tef grain milled to optimum level of
fine powder are preferred in injera making. The grain
composition in the 13 tef grain varieties are of typical
for tef grain reported elsewhere with no amylo- or
waxy-type starch traits. The slight variations in the
pasting characteristics might be used to assess the
injera making and keeping quality variations and in
other tef grain foods. The dependency of SB (gelation
tendencies) on amylose in tef flour starch pasting is
found weak. It seems tef flour starch pasting is
different in this aspect from normal cereals like wheat,
rice, sorghum and maize.
ACKNOWLEDGEMENT
The D ZTIP for providing tef grain varieties,
the Ethiopian Institute of Agricultural Research and
the IFS-O PCW (E/3173-2) for the financial support;
and colleagues at the department of Food Science
and Post harvest T echnology, H aramaya University
for their technical support are acknowledged for
this work.
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