effect of baking ingredients and mixing duration on dough development, gas release and bread making...
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EFFECT OF BAKING INGREDIENTS AND MIXING DURATION ON DOUGH DEVELOPMENT, GAS RELEASE
AND BREAD MAKING PROPERTIES
NARPINDER SINGH', HARDEEP SINGH GUJRAL and JASPREET SINGH
Department of Food Science Md Technology Guru Nanuk Dev University
Amritsar-143005. India
Accepted for Publication July 25, 2001
ABSTRACT
Three trials were carried out to determine the @ect of wet gluten, acetic acid, fat, sodium chloride and mixing duration on dough development, gas release and bread characteristics wing regression analysis. Maximum dough height was significantly aflected by acetic acid, wet gluten, mixing duration and sodium chloride whereas maximum gas formation was significantly affected by acetic acid and sodium chloride levels. The addition of fat had signijicant G e m on bread volume. Sodium chloride affected overall acceptability followed by wet gluten, mixing duration and fat levels. Bread volume and overall acceptability decreased with an increase in mixing duration. Increased levels of sodium chloride increased bread volume and overall acceptability and decreased CO, production. Addition of fat at a level of more than 3% caused a decrease in acceptability. Bread volume and acceptability progressively increased with the increase in wet gluten levels.
INTRODUCTION
A large number of optional ingredients such as hydrocolloids, skim milk, fat, acids, emulsifiers and gluten are included in bread formulation to improve its nutritional, shelf-life and organoleptic properties (Hoseney 1986). Salt gives flavor to bread and also acts as a dough strengthener (Hoseney 1986). Fat acts as a plasticizer, gives softness, improves volume and has anti-staling properties when added to a bread formula. Brooker (1996) reported that during baking fat crystals melt and thereby make it possible for the crystal-liquid interface to be incorporated into the surface of the bubble as it expands. This transfer of interfacial material from crystals to bubble surface explains how the addition of
'Correspondent Author
Journal of Food Quality 25 (2002) 305-315. All Rights Resewed. mCopyright 2002 by Food & Nutrition Press. Inc., Trumbull, Connecticut. 305
306 N . SINGH, H. SINGH GUJRAL. and J. SINGH
shortening to dough allows bubbles to expand during baking without rupturing, thus producing high volume of bread with fine crumb structure. Acetic and lactic acids are used in bread formulation to improve the shelf-life of bread. Treatment of flour with acetic acid has been suggested as an alternative to potassium bromate and ascorbic acid in bread making (Seguchi et al. 1997).
Dough mixing duration has a significant effect on rheological and baking properties. Under mixed dough will have unhydrated starch and protein which cannot interact in the dough during fermentation (Hoseney 1986). On the other hand over mixing leads to the formation of wet, sticky dough which poses problems during handling. The quality of bread dough depends on mixing conditions such as mixer type, rotation speed, mixing time and water content.
The present study using regression analysis reports the effect of additives (acetic acid, fat, sodium chloride and wet gluten) and process variable (mixing duration) on dough development and gas release characteristics during fermentation and bread making properties.
MATERIALS AND METHODS
Materials
Acetic acid and sodium chloride of analytical grade were obtained from SD Fine Chemicals (S.D. Fine-Chem-Ltd., Mumbai). Bakers compressed yeast (Tower Brand, Calcutta) was used. Hydrogenated vegetable fat (Dalda brand, Hindustan Lever Ltd., Mumbai) was procured from the local market. Wet gluten was extracted by the hand washing method (AACC 1995) and used as described earlier (Singh et al. 1991).
Preparation of Samples
Bread wheat (variety PBW-343) was procured from the 1999 harvest at Punjab Agriculture University, Ludhiana. The wheat was cleaned and then conditioned to 14% moisture content. The wheat was milled into flour in a laboratory mill (Barbender Junior Quadrumatic Mill, Duisburg, Germany). The flour had an extraction rate, 75%, protein, 9.6%, ash contents, 0.40% and a Falling Number value of 510 s.
pH Determination
Dough (10 g) was mixed in 100 mL water and pH of the extract was measured using a digital pH meter (Elico Ltd. Hyderabad) as described earlier (Sekhon et a2. 1995). The pH of the dough was 6.4, 6.2, 5.8, 5.6 and 5.3
BAKING INGREDIENTS AND MIXING DURATION FOR BREAD 307
when acetic acid was added at levels of 0, 0.05, 0.1, 0.15 and 0.20% (flour weight basis), respectively.
Dough Development and Gaseous Release Characteristics
Weighed quantities of compressed yeast (5 g), salt (variable) and acetic acid (variable) were mixed in small quantity of distilled water separately. These were mixed with flour (200 g), fat (variable), wet gluten (variable) and water (optimum) in a laboratory mixer (National Manufacturing Company, Lincoln, NE) for the desired mixing duration (variable). The salt solution was added to the dough during the last minute of mixing. The kneading was finished at 30C into a smooth dough by stretching and folding manually. Maximum dough height (H,,,) in mm, maximum height of gaseous release (H,.) in mm, CO, production in mL were measured in duplicate using Rheofemntometer (Chopin, Tripette & Renaud, France) as described earlier (Singh ef al. 1990).
Bread Making
Wheat flour (200 g), compressed yeast (5 g), sodium chloride (variable), acetic acid (variable), fat (variable) and wet gluten (variable) were mixed with adequate quantity of water to get a dough of moderate stiff consistency (Singh el at. 1998). All the ingredients were mixed for different mixing duration in a mixing bowl of a laboratory mixer (National Manufacturing Co., Lincoln, NE). The kneading, fermentation, molding, proofing and baking was done as described earlier ( b u r and Singh 1999). Breads were prepared in triplicate and were organoleptically evaluated by a panel of ten persons as described earlier (Singh et al. 1990).
Statistical Analysis
Regression analysis was performed using the central composite design to determine the effects of five independent variables on dough development, gaseous release and bread making properties. The five independent variables were sodium chloride (X'), mixing duration (XJ, acetic acid (XJ, fat (X,) and wet gluten (X5). The dependent variables were H,, H,,, COz production, bread volume and overall acceptability scores. Each variable was tested at five levels. The central composite design consisted of 30 tests performed in triplicate (Table 1).
TABL
E 1.
EX
PERI
MEN
TAL
DES
IGN
AN
D T
EST
RESU
LTS
Sod
ium
M
ixin
g
Ace
tic a
cid
Fat
Wet
Sl
uten
H
,,,
[I,,,
CQ
pro
duct
ion
Brea
d O
vera
ll ~
Trea
tmen
t ch
lori
de ("
4,)
duia
tion
(min
) (I
%)
(%)
(Yo)
(m
in)
(rnm)
(ml)
vo
lum
e (ml)
acce
ptab
ility
scor
es
1 0
8
3 0
05
10
4
5
346
85 5
19
22
807
75 0
0 2 3 4 5 6 7 8 9 10
I1
12
13
14
I5
16
17
18
19
20
21
22
23
24
-_
?5
26
27
-78
29
30
0.8
0.8
0.8
0.8
0.8
0.8
0.8
2.4
2.4
2.4
2.4
2.4
2.4
2.4
2.4
0 32
1.
6 1.
6 1.
6 1.
6 1.
6 1.
6 I .
6 I 6
I 6
I 6
1 .
6 1.6
3 3 3 7 7 7 7 3 3 3 3 7 7 7 7 5 5 1 9 5 5 5 5 3 3 > 3 5 5
0.05
0.15
0.15
0.
05
0.05
0.
15
0.15
0.
05
0.05
0.
15
0.15
0.
05
0.05
0.
15
0.15
0.
10
0.10
0.
10
0.10
0.
00
0.20
0.
10
0. I
0 0
10
0.10
0.
I0
0. I0
0.
10
0.10
3.0
1 .o
3.0 1 .o
3 .
O 1 .o
3.
0 1 .o
3.
0 1 .o
3.
0 1 .o
3 .
O 1 .o
3 .
O 2.
0 2.
0 2.
0 2.
0 2.
0 0 4.
0 2.
0 2.
0 2.
0 2.
0 2.
0 2.
0 2.
0
1.5
1.5
4.5
1.5
4.5
4.5
1.5
I .5
4.5
4.5 1.5
4.5
1.5
I .5
4.5
3.0
3 .O
3.0
3.0
3 .O
3.0
3.0
3.0
0.0
6 0
.: ,o
3 0
3 .O
3 .O
30.0
84
.8
34.9
60
.5
37.5
90
.1
22.7
86
.4
32.1
90
.0
27.6
89
.4
26.4
96
.4
34.8
66
.2
40.2
69
.3
42.8
73
.0
39.0
73
.5
29.9
72
.1
29.3
70
.0
28.7
73
.5
30.5
71
.0
25.7
91
.2
37.0
59
.4
37.0
71
.5
25.9
86
.3
27.5
72
.2
34.5
84
.0
28.6
74
.5
30.0
72
.2.
27.2
78
.0
32.5
77
.4
3 I 2
04
.0
3 I 0
62
.9
30.1
58
.0
32.7
68
.0
1850
1384
2010
19
49
1997
20
25
2059
14
20
1512
16
37
1503
15
60
1500
15
40
1496
I9
97
1235
15
81
I890
I6
02
I829
17
23
1643
17
50
1750
I4
00
1434
13
50
1510
840
795
960
697
735
600
GI5
850
960
85 5
925
745
705
707
745
745
895
940
620
770
775
710
800
670
S40
768
785
775
770
72.5
0
70.0
0
84.5
0 64
.00
65.0
0 58
.00
53.0
0 80
.00
83.0
0 79
.00
80.2
5 70
.50
68.5
0 67
.25
68.5
0 63
.50
78.5
0 78
.00
60.7
5 73
.50
69.0
0 68
.50
70.5
0 63
.70
76.5
0 74
.00
75.0
0 73
.00
76.0
0
BAKING INGREDIENTS AND MIXING DURATION FOR BREAD 309
RESULTS AND DISCUSSION
To predict the relationship between dependent variables (Y) and independent variables (Xi>, the regression model used was:
5 5 5 5 5
j-1 j=2 j=3 J =4 j-1 Y = a + c ~ j X ~ + c ( c j X l X ~ + c ( d j d j X 2 X j ) + ~ ( e j X 3 X j ) + f s X 4 X ~ + ~ ~ j X ~ )
Where a, b, c, d, e, f and g are regression coefficients (Table 2). All the models correlated well with the measured data and were significant at PC0.002. R2 values of all the models was sufficiently high; they ranged between 91.7-98.5%, indicating that they were appropriate.
Maximum Dough Height (H,) H, is the height of maximum dough development during fermentation. The
results in Table 2 showed that 93.5% (R2 = 0.935) of the H, variability can be explained by the regression model. Acetic acid showed the most pronounced effect on H, value followed by wet gluten, mixing duration and sodium chloride levels (P<0.3). sodium chloride and mixing duration showed significant effect on H, value at p value in linear terms of less than 0.3. Sodium chloride interaction with fat and acetic acid showed a significant effect on H,. Acetic acid and fat levels also interacted significantly in effecting H, value. H, increased with the increase in gluten, sodium chloride and acetic acid and decreased with an increase in mixing duration. The adverse effect of increased mixing duration on H, decreased with the increase in wet gluten levels (Fig. 1). Acetic acid did not show any positive effect in overmixed dough (more than 3 min). H, increased with the increase in fat levels in the absence of acetic acid. An increase in acetic acid levels decreased the improving effect of fat. The improvement in H, was more in the presence of gluten. The change in H, with sodium chloride was more pronounced in the absence of gluten and acetic acid. Sodium chloride decreased the adverse effect of over mixing on H, value. Wehrle ef al. (1997) reported that the salt strengthens dough structure and reduces the effects of overmixing. The decrease in H, with sodium chloride may be attributed to its toughening effect on gluten and of acetic acid to a reduction in -SH groups. It has been reported that reducing the pH results in a reduction in -SH groups (Tsen 1966).
Maximum Height of Gaseous Release (&.)
H,. is the height of maximum gas formation during fermentation. The regression analysis showed that 94.3% variability in H,. can be explained by the
TABL
E 2.
CO
EFFI
CIEN
T A
ND
SIG
NIF
ICA
NCE
OF
REG
RESS
ION
MO
DEL
S
Term
H,
,, H
,,,
(‘O?
Bre
ad
Ove
rall
Con
stan
t (a)
21
.92
96.9
20
24
794.
4 58
. I pr
oduc
tion
volu
me
acce
ptab
ility
sco
res
Sodi
um c
hlor
ide
(b,)
M
ixin
g du
ratio
n (b
?)
Ace
tic a
cid
(b,)
Fat l
evel
s (b
4)
Wet
glu
ten
leve
ls (b
s)
Sodi
um ch
lorid
e x
Mix
ing
dura
tion
(c?)
So
dium
chlo
ride
x A
cetic
aci
d(c,
) So
dium
chlo
ride
x Fa
t lev
els
(c,,)
So
dium
chlo
ride
x W
et g
lute
n le
vels
(cj
) M
ixin
g du
ratio
n x
Ace
tic a
cid(
d3)
Mix
ing
dura
tion
x Fa
t lev
els
(d4)
M
ixin
g du
ratio
n x
Wet
glu
ten
leve
ls (d
,) A
cetic
aci
d x
Wet
glu
ten
leve
ls (e
,) A
cetic
aci
d x
Fat l
evel
s (e
j)
Fat l
evel
s x W
et g
lute
n le
vels
(f5)
Sodi
um ch
lorid
e x
Sodi
um c
hlor
ide
(g,)
M
ixin
g du
ratio
n x
Mix
ing
dura
tion
( g2)
A
cetic
aci
d x
Ace
tic a
cid
(g,)
Fa
t lev
els x
Fat
leve
ls (g
,) W
et g
lute
n le
vels
x W
et g
lute
n le
vels
(gi)
S
04 o”
:, 98%
97,7
’%,
*P<0
.3,
**P1
0.03
, ***
PSO
.003
4.08
*
96.3
9*
0.39
2.
57*
- 1.7
9*
-0.4
0*
-0.0
3 1
-0.2
7 -0
.32
-9.6
2*
0.3 1
* -0
.07
-12.
75*
-8.8
3*
0.08
0.
67
0.1
I*
137
0.03
0.
02
2.16
93
.5%
-8.9
* -2
.4
-47
1.8 *
**
2.8
0.3
-1.4
* 37
* -3
.2*
-1.3
* 12
.8*
-0.8
* -0
.8*
38.4
8.
4
4.2*
* 0.
9***
13
43.5
**
2.2*
I .
4**
4.47
94
.3
-1.6
-125
-1
0 -8
724*
* 17
1 -3
3*
662*
-6
1*
-24*
17
7 -1
7*
-19*
59
2*
342
-31*
57
* 17
**
2449
0**
53**
31
**
95.9
5
-33.
5 6.
9*
-1 1.
2 I .
4 26
3.3
18.2
36
.6*
3.1
10.2
2.
8*
2.6
0.6
126.
6 6.
2 -5
.7
-0.4
-1
.9
-0.9
* -1
83.1
**
-15.
3*
-10.
2**
-0.7
’ -1
.5
0.2
183.
7 15
.6*
-30.
8*
9.2
14.9
**
1.1*
19
.9**
-0
.7
0.7
-0.2
* 34
5.0
-164
.5
-3.5
-0
.8*
-1.6
-0
.3”
24.7
2 2.
75
BAKING INGREDIENTS AND MIXING DURATION FOR BREAD 311
I
0 1 2 3 4 5 6 7 8 9
Mixing duration (min)
FIG. 1. CONTOUR RESPONSE SURFACE PLOT SHOWING THE EFFECT OF GLUTEN AND MIXING DURATION ON H,,,
regression model (Table 2). Acetic acid showed highly significant effect on H,. both in linear and squared t e r n (PS0.003). Sodium chloride also showed a significant effect in linear and squared terms at p values of less than 0.3 and 0.03, respectively. Mixing duration, wet gluten and fat levels showed significant effect on H,. in squared terms only. The interaction effect of fat with sodium chloride and wet gluten; and mixing duration and wet gluten on H,. was significant at p values of less than 0.1. H,. decreased with an increase in sodium chloride and increased with an increase in fat. The increase in H,. caused by an increase in mixing duration decreased with the increase in sodium chloride levels. The decrease in H,, with the increase in sodium chloride level may be attributed to a decrease in COz production. The effect of sodium chloride on H,, was predictable from regression models where the level of sodium chloride was varied and the levels of acetic acid, wet gluten, fat and mixing duration were constant at their central levels (Fig. 2). H,. decreased with the increase in sodium chloride levels. Similar effects of mixing duration and sodium chloride have been observed earlier (Gujral and Singh 1999).
312 N. SINGH, H. SINGH GUJRAL and J . SINGH
80 k 100 r -Hm’
h C 0 2 production
y’ayl. 60 70 I
0 1 2 3 ‘I Sodium chloride (“10)
FIG. 2. EFFECT OF SODIUM CHLORIDE ON H,,, AND CO, PRODUCTION Values calculated using regression models.
CO, Production
Statistical analysis indicated that the model developed for total COz production during three hours fermentation in the RheofermentometerF, vat was adequate (Table 2). The statistical analysis showed acetic acid as the most prominent factor affecting CO, production both in linear and squared terms (PsO.03) . Wet gluten, sodium chloride, mixing duration and fat also showed significant effect on CO, production, however in squared terms only. CO, production increased with the increase in acetic acid, wet gluten and mixing duration and decreased with the increase in sodium chloride levels. The increase in CO, production with the increase in acetic acid may be attributed to the decrease in dough pH towards optimum pH for a-amylase. The pH of dough decreased from 6.4 to 5.6 and 5.3, respectively, with the addition of 0.15% and 0.20% of acetic acid. CO, production decreased with the increase in sodium chloride concentration (Fig. 2). A decrease in total CO, production with an increase in sodium chloride level has also been observed by Takano ef al. (1996). Similar effects of wet gluten on CO, production has been reported earlier (Singh ef al. 1998).
BAKING INGREDIENTS AND MIXING DURATION FOR BREAD 313
Bread Characteristics
The statistical analysis revealed that 98 X of the variability in bread volume was explained by the regression model (Table 2). The fat level showed a significant effect on bread volume in linear terms while sodium chloride showed a significant effect in squared terms. Fat levels in interaction with mixing duration and wet gluten showed highly significant effect (PCO.01). The contour surface plot shows that the improving effect of fat on bread volume decreased with an increase in mixing duration (Fig. 3). An improvement in bread volume with the addition of gluten was observed to increase with the increase in fat levels. Mixing duration and acetic acid interaction effects on bread volume were also significant (PC0.02). Bread volume increased with an increase in wet gluten, fat and sodium chloride and decreased with the increase in mixing duration. The increase in bread volume with the addition of fat may be attributed to stabilization of gas cells in dough. Brooker (1996) reported that during baking fat crystals melt and thereby make it possible for the crystal-liquid interface to be incorporated into the surface of the bubble as it expands, This transfer of interfacial material from crystals to bubble surface explains how the addition of shortening to dough allows bubbles to expand during baking without rupturing, thus producing high volume of bread with fine crumb structure. Similar effects of wet gluten, fat and mixing duration have been reported earlier (Singh et al. 1998; Elton and Fisher 1966). The addition of fat and acetic acid beyond 3% and 0.1 X levels, respectively caused deterioration in overall acceptability scores.
0 1 2 3 4 5 6 7 8 9
Mixing dimtion (mill)
FIG. 3. CONTOUR RESPONSE SURFACE PLOT SHOWING THE EFFECT OF FAT AND MIXING DURATION ON BREAD VOLUME
3 14 N. SINGH, H. SINGH GUJRAL and J. SINGH
CONCLUSIONS
In summary, acetic acid showed significant effect on H, followed by wet gluten, mixing duration and sodium chloride whereas H,. was significantly affected by acetic acid followed by sodium chloride. Fat addition showed significant effect on bread volume whereas overall acceptability scores were significantly affected by sodium chloride followed by gluten. The highest bread volume was 960 mL and overall acceptability, 84.5. The regression models allows the determination of additive levels and mixing conditions that can result into bread having bread volume and overall acceptability above the values obtained in the study here. The mixing of dough containing 1.6% sodium chloride, 0.15% acetic acid, 3% fat and 4.5% wet gluten for 3 min can result in dough having H,, H,. and CO, production of 38 mm, 78.2 and 1780 mL and bread volume of 973 mL and an overall acceptability score of 86.5.
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BAKING INGREDIENTS AND MIXING DURATION FOR BREAD 315
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6 10-6 16.