Effect of Roasting on Quality of Bajra and Sattu

Abstract

Roasting has a significant impact on the quality of the final product. In order to see the effect of roasting on
geometric mean diameter, colour. hardness, toughness. average rupture force and sensory attributes of bajra for making sattu, bajra was roasted at three temperatures (160, 130 and 200°C) for a time period of45, 60 and 75 sec. In general. geometric mean diameter, hardness, toughness and average rupture force increased with increase in roasting temperature. Roasting brought a significant change in colour ofbajra grain and roasted bajra flour samples. ho and C* of bajra flour increased with increase in time at the same roasting temperature except at 180°C for 45 s time. Roasting of bajra at 180°C for 60 s was found to be best for making sattu. The 10% level of bajra flour with bengal gram (90%) was found the most accepted sattu formulation.

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Journal
of
Agricultural Engineering
Vol.
43(4): October-December, 2006
Effect
of
Roasting on Quality
of
Bajra and Sattu
D.
Mridula
1
,
M. R. Manikantan
2
,
R.
K.
GoyaP
and
O.
D.
Wanjari
4
ABSTRACT
Roasting has a significant impact on the quality
of
the final product.
In
order to see the effect
of
roasting on
geometric mean diameter, colour. hardness, toughness. average rupture force and sensory attributes
of
bajra for
making
sattu, bajrawas roasted at three temperatures (160, 130 and 200°C) for a time period
of
45,
60
and 75 sec.
In
general. geometric mean diameter, hardness, toughness and average rupture force increased with increase
in
roasting temperature. Roasting brought a significantchange
in
colour
ofbajra
grain and roasted bajra flour samples.
ho and
C*
of
bajra flour increased with increase
in
time at the same roasting temperature except at 180°C for 45 s
time. Roasting
of
bajra at 180°C for
60
s was found to be best for making sattu. The 10% level
of
bajra flour with
bengal gram (90%) was found the most accepted
sattu formulation.
Traditional foods have played an important role in our
diet for generations. Amongst various traditional foods,
cereals and
pulses
based
products
still
occupy
an
important
place
in
diets
of
people
particularly
in
developing
countries.
The
important
traditional
products, which are still
popular among Indian
population,
are sattu, papad,
wadian, puffed rice, flaked rice, etc. Sattu is basically
roasted flour made from cereals only,
or
legumes only
or, combination
of
cereal
and
legumes with
added
flavouring agents.
Roasting
is a
simple
and
more
commonly used household and village level technology,
which pre-cooks the ingredients used
in
food grains
and oilseed based mixes
and
increases
shelf
life and
acceptability
of
the products. Roasting improves the
flavour, texture and nutritive value
of
the grains (Siegal
and Fawcett, 1976), eliminate most
of
anti-nutritional
or toxic effects
oflegumes,
partially
or
wholly (Liener,
1973).
Bengal gram
is
the preferred legume for making sattu,
particularly in Bihar and eastern Uttar Pradesh but no
legume or cereal alone can provide balanced amount
of
nutrients. However, mixing
of
legume with cereal
can improve the overall nutrition. Supplementing various
types
of
millets
with
chickpea
has
shown
good
improvement
in
the protein efficiency ratio (Casey and
Lorenz, 1977). Addition
of
cereal and millets to sattu
to the acceptable limit will not only improve the protein
quality
but
also
reduce
the
cost.
Nowadays
the
popularity
of
Bengal gram sattu is also
increasing
amongst the diabetics due to its low glycemic index.
Due to lower glycemic response
ofbajra
(Shukla et.al.,
1991), bajra based
sattu can also getpopularity amongst
the masses
at
lower
cost
than pure bengal gram based
sattu. Studies (Vimala
et
aI., 1990; Dahiya and Kapoor,
1995) have been
conducted
to develop the weaning
mixes based on the pearl millet(bajra) and Bengal gram
but information on optimum roasting conditions
ofbajra
for making sattu is not available. Therefore, the present
study was undertaken with the objective to standardize
the roastingtemperature and time combination for bajra
for making
sattu in combination with Bengal gram.
MATERIALS
AND
METHODS
Bajra (variety FBC-16) with
GMD
(geometric mean
diameter) 2.28 mm was used for the study.
In
order
to see the effect
of
roasting on quality
of
bajra for
making
sattu with bengal gram, bajra incorporated sattu
was
prepared.
Raw
bajra
with
moisture
content
of
9.58%
(w.b.) was dipped twice
in
water
in
a wire mesh
basket for
washing
followed
by
tempering
for
two
hours. The moisture
content
of
the tempered samples
was in the range
of
15.85 - 16.02 % (w.b.). The washed
and tempered samples were roasted in sand using sand
grain ratio
8:
I at three different temperatures (160, 180,
200°C)
and
time
(45,
60, 75 s)
combinations.
The
roasted samples were tempered for 4
h,
packed
in
LOPE
bags (62.5
fl) and kept in desiccator for determination
of
moisture, colour, and textural properties. The roasted
samples were subjected to
CIAE
cleaner cum grader
Food Grains & Oilseeds Processing Division, Central Institute
of
Post Harvest Engineering & Technology, Ludhiana
14/
004 (E-mail:
rnridulads4@yahoo.co.in)

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October-December,
2006
Effect
of
Roasting on Quality
of
Bajra and Saltu
to remove the sand particles,
if
any, before grinding
for making flour. The ground samples were evaluated
for colour and different sensory attributes. Bengal gram
and bajra based
sattu was prepared from bajra flour,
prepared from bajra roasted at 180°C for 60s. Different
formulations with roasted Bengal gram were prepared
using bajra at 10, 20, 30 and 40% level. Statistica
7.1
was used for statistical analysis
of
the results
of
the
study.
known as the lightness and extends from 0 (black) to
100 (white).
The
other
two coordinates
a*
and
b*
represents
redness
(+a)
to
greenness
(-a)
and
yellowness (+b) to blueness (-b), respectively.
hO
(hue
angle) is the attribute
of
colour
by
means
of
which the
colour is perceived. C* (chroma) is the attribute
of
colour used to indicate the degree
of
departure
of
the
colour from gray
of
the same lightness.
hO
and
c*
were computed using the following formula.
RESULTS AND DISCUSSION
Textural properties
of
the roasted bajraare very important
because energy requirement for grinding may be
in
proportion to the hardness and average rupture force.
Hardness ofbajragrain increased with increase
in
roasting
temperature and time (Table
I).
The reason for the
increase
in
hardness at increased temperature and time
may be due to decrease
in
moisture content
of
the grain
in
the roasting process as also found
in
other studies
Sensory Evaluation
Sattu was evaluated for different sensory attributes
by
a
panel
of
nine trainedjudges. Sensory attributes like colour
and appearance, body (textural property
of
sattu drink),
roasted odour, flavour, taste and overall acceptability
for all samples were assessed using nine point hedonic
scale (IS: 6273, 1971). Hedonic scale was
in
the following
sequence- like extremely -9, like very much -
8,
like
moderately -7, like slightly -
6,
neither like nor dislike-
5,
dislike slightly
4,
dislike moderately, -
3,
dislike very
much - 2, dislike extremely -
I (Larmond, 1977).
Roasting has a significant impact on the overall quality
of
grain and the final product i.e. sattu. The roasting
flavor, the most desired quality
of
sattu depends
on
the
roasting
temperature
and
time.
Hence,
roasting
temperature and time combination
is
of
great importance
in
processing the grain for making sattu. It
is
observed
from Fig.1
that
moisture
content
of
roasted grain
decreased with increase in both roasting temperature
and time.
GMD
increased with increase
in
roasting
temperature and time, Fig.
2.
The increase
in
GMD
in
linear fashion may be attributed to start
of
puffing
of
grain at high temperature and time combination.
where b
=
b*,
a
==
a*
hO
=
tan-I
(b/a)
C*
= a
2
+ b
2
Geometric Mean Diameter
Geometric mean diameter is the geometric mean
of
the
spatial dimensions
of
raw and roasted grain, were
measured using Vernier Caliper with least count
of
0.02
mm. The spatial dimensions namely length (L, longest
dimension), breadth (B, second longest dimension),
thickness (T, least dimension) were measured for
10
representative seeds under
each
roasting condition.
Geometric mean
of
the spatial dimensions was calculated
as:
Textural Properties
The textural properties
of
raw and roasted bajra grain
such as hardness, toughness and average rupture force
were measured using Texture Analyzer
TA-HDi, Stable
Micro systems, UK. The
TA
setting were: mode- measure
force in compression, option-return to start, pre test
speed- 3
mmls, test speed - I mmls, post test speed -
10
mmls, distance- I mm, trigger force - 20
g,
stainless
steel cylinder probe - 5 mm diameter (PIS), and 50
kg
load cell. Textural properties were measured for
10
representative seeds
of
each replication under each
roasting condition. Duringthe test, the graph was drawn
between force and distance as the result
of
the force
resisted by the grain sample against the probe
of
texture
analyzerwith the help
of
software (Texture Expert Exeed
TM).
The maximum force experienced
by
the probe was
considered as hardness and thearea underthis maximum
force on the graph was considered as toughness
of
the
grain. The average force experienced by the probe
throughout the test
is
considered as average rupture force
of
the grain.
Equivalent diameter
= (L x B x
T)I/3
Colour Determination
Colour
(L*,
a*,
b*
values)
of
the
samples
was
determined using Handy Colorimeter NR-3000. L* is
66

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D.
Mridula,
M.
R.
Manikantan,
R.
K.
Goyal and
O.
D.
Wanjari
JAE : 43(4)
8-,----------------.
granules, leads to difficulty
in
separating starch from
protein
and
makes
the grain
harder
(Stenvert
and
Kingswood, 1977; Moss
et
al.,1980). This may also
be one
of
the reason for increased hardness
of
bajra
grain. Hardness was also increased with increase in
the roasting temperature for the same roasting time.
The hardness
of
bajra at 200°C for 60s, although not
significant but lowered as compared to 75s roasting
time than at 160 and 180°C. This may be due to the
fact that surface gelatinization
of
starch took place
initially and fissures developed onthe grain upon further
heating, resulted in the reduced hardness.
80
70
60
50
O+-----r----,------r-----i
40
Roasting
tirre,
sec
Fig.
I:
Moisture
of
roasted
bajra
grain
2.7
.,----------------,
Fig.2: Effect
of
roastingon
GMDofbajra
.
---------
2.3
•
The
colour
of
the
sattu
is
very
important
from
consumer points
of
view because it
is
the colour, which
appeal first to a person to purchase or consume any
food. Roasting, affected the colour
ofbajra
grain (Table
2). L* value
of
bajra grain at 160° C decreased with
increased roasting time while at 180° and 200° C, L*
value slightly decreased at 60 s as compared 45
sand
further increased at 75s time. The variation
in
L* value
at different time and temperature combinations may be
due to degree
of
puffing
of
bajra grain. At the same
temperature when roasting time was increased, no
significant changes was observed in
a*
value except at
200°C. The decrease
in
a*
value at 200°C may be due
to slight puffing
of
some
of
grains, which increased
the
L*
value i.e. whiteness and decreased the redness
i.e.
a*
value Overall colour changes during heating took
place due to Maillard reaction (Ibanoglu 2002). When
the roasted bajra was milled into flour,
hO
(hue) and
c*
(chroma) showed a different pattern because
of
the
colour
of
the endosperm. In the seed form, colour
80
50
60
70
Roasting
tirre,
sec
--+--
16O"C
--·180"C
___
200"C
_____________
~~-----
2.2
f---.,....----,----,r------'1
40
2.6
~
2.5
g
2.4
(Srivastav et a!., 1994). Hardness
of
bajra decreased
when roasted at 160°C for 45s time compared to raw
grain but when time increased, hardness also increased.
This trend was also observed at other temperatures
i.e. 180 and 200°C. The formation
of
a continuous
protein matrix, which
physically
traps
the
starch
Table
1.
Effect ofroasting on textural properties
of
bajra
(whole grain)
Temperature,
Time,s
Hardness, N
Toughness,
Average rupture
°C
N-mm
force, N
Raw grain
30.38
3.64
9.54
160
45
19.36
3.11
5.95
60
25.18
3.28
8.33
75
33.17
6.34
12.35
180
45
23.96
5.29
9.22
60
27.56
6.93
9.90
75
40.12
8.09
10.65
200
45
35.92
6.12
13.96
60
45.63
6.99
14.16
75
45.15
9.31
14.51
CD
(p
<0.05)
6.42
1.57
2.51
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October-December, 2006 Effect
of
Roasting
on
Quality
of
Bajra
and
Sattu
Table
2.
Effect
of
roastingon colour
ofbajra
(whole grain)
Temperature,
DC
Time,s
L*
value
a*
value
b*
value
hO
C*
160
45
42.31
5.67
14.91
69.18
15.95
60
41.88
6.03
13.82
66.43
15.08
75
40.00
5.17
13.83
69.50
14.76
180
45
44.62
5.71
17.06
71.49
17.99
60
42.39
6.18
14.84
67.39
16.08
75
45.74
5.89
15.13
68.73
16.24
200
45
44.15
7.46
17.09
66.42
18.65
60
43.11
6.57
15.66
67.24
16.98
75
44.57
6.01
15.55
68.87
16.67
CD (p <0.05)
2.07
0.82
1.48
3.40
1.28
represents the colour
of
the seed coat while
in
ground
form; it is
the
mixed
effect
of
the
colour
of
all
component
of
the grain. L* values for bajra flour,
prepared from grain roasted
at
different
time and
temperature were not significant but effect
of
roasting
on
a*
and
b*
values for bajra flour (Table 3) brought a
significant change in
hO
(hue) and C* (chroma)
ofbajra
flour, which has atso affected the acceptability
of
the
product.
Mean sensory scores
of
roasted bajra flour for making
sattu are given
in
Table
4.
The mean scores for all the
attributes and overall acceptability were more than the
minimum
acceptable
score
of
5. The results
thus
indicated that the samples
of
bajra flour prepared from
grain roasted at different roasting conditions were
accepted by the panelist with highest score for roasted
odour (6.58) and overall quality (6.58)
of
the samples
Table3. Effect
of
roastingon colour
of
bajra
flour
prepared from the grain roasted at 180
0
C for 60 s,
hence this sample was used for making bengal gram
and bajra based sattu.
AIthough, the mean sensory
scores for different sensory attributes were within the
acceptable range except for 40% bajra incorporated
sattu
for
colour
and
appearance
but
10%
bajra
incorporated sattu was well accepted when compared
with the control
in
drink form (Table 5).
The result
of
ANOYA
for each characteristics
from
each
individual score
of
sensory panel for different samples
of
roasted bajra flour and bajra incorporated sattu
revealed that the difference among the various products
was significant for all the attributes. This
may
be
due to
effect
of
roasting conditions
of
different samplesofbajra
flour and level
of
bajra flour
in
the sattu formulations.
Further, variance due to judges did not exist, indicating
that panelist group was homogenous.
Temperature,
DC
160
180
200
CD
(p <0.05)
Time,
L*
value
a*
value
b*
value
hO
C*
sec
45
62.54
5.44
9.91
61.24
11.30
60
62.58
5.19
9.58
61.55
10.90
75
62.65
5.06
10.63
64.55
11.77
45
64.61
4.78
11.99
68.26
12.91
60
64.35
5.20
11.35
65.39
12.48
75
64.00
5.25
12.18
66.68
13.26
45
63.73
4.97
11.08
65.84
12.14
60
63.69
5.11
12.16
67.21
13.19
75
62.94
5.39
13.22
67.82
14.28
NS
0.21
1.11
2.24
1.15
68

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D.
Mridula,
M.
R.
Manikantan,
R.
K.
Goyal
and
0
D.
Wanjari
Table
4.
Effect
of
roasting on mean score
of
sensory paneljudges for different characteristics
of
baj
ra
flour
Roasting temperature
Colour and
Roasted odour Overall
and time (deg C/ s)
appearance
acceptabiIity
160/45
5.66
5.68
6.04
160/60
5.89
6.02
5.58
160/75
6.03
6.44
6.15
180/45
6.06 6.02
6.12
180/60
6.28
6.58
6.58
180/75
6.22
6.14
6.02
200/75
5.67
5.89
5.79
200/60
6.25
6.23
6.07
200/75
6.21
6.13
6.13
CD
(p<0.05)
0.0199
0.023
0.028
JAE : 43(4)
Table
5.
Mean score
of
sensory paneljudges for differentcharacteristics
of
bengal
gram
and
bajra
basedsattu
Proportion
of
Colour and
Body Roasted Flavour and Overall
bengal gram : bajra appearance odour
taste acceptability
90:10
6.86
6.53
6.92
7.17
7.01
80:20
5.89
6.22
6.31
6.03
5.94
70:30
5.28
5.81
6.05
5.58
5.67
60:40
4.76
5.69
5.83
5.56 5.39
100:0
(control)
7.73 7.44 7.13
7.92
7.35
CONCLUSIONS
Roasting
of
bajra grain at
different
temperature
and
time combination affected
the
GMD
and
hardness
of
bajra, and
colour
ofbajra
and
bajra
flour. Hardness
of
bajra
grain
increased
with
increase
in
roasting
temperature
and
time.
The
lower
hardness
of
bajra
roasted at 180°C for
60
s
was
found
most
suitable for
making sattu.
The
10% level
ofbajra
flour with bengal
gram
(90%)
was
found
the
most
accepted
sattu
formulation with mean
sensory
score
(7.0
I)
at 9 point
hedonic scale.
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