IMPROVEMENT OF BAKING CHARACTERISTICS BY
TRANSGLUTAMINASE ADDITION
M. Benković, D. Novotni, D. Tušak, M. Krpan, I. Bauman, D. Ćurić
University of Zagreb, Faculty of Food Technology and Biotechnology
Pierottijeva 6, 10000 Zagreb
mbenkovic@pbf.hr
ABSTRACT
Transglutaminase (TG) has been successfully used in food systems to promote
protein cross-linking. The aim of this paper was to investigate the effects of
microbial TG on whole meal wheat dough and bread quality parameters in case of
salt reduction. Gluten cross-linking was done by microbial transglutaminase
preparation Activa WM. Control sample was baked without TG (salt content 1.8
g/100 g flour). TG concentration varied from 0.10 g/100g flour to 0.30 g /100 g
flour and salt from 1.20 g/100 g flour to 1.8 g/100 g flour. The effect of TG was
evaluated by dough rheological tests and bread physical tests, texture profile
analysis and sensory analysis. TG addition had a negative impact on dough
consistency, softening and extensibility, but improved resistance to extension.
Concentrations of TG higher than 0.12 g/100 g flour caused a decrease in specific
volume and an increase of crumb hardness, gumminess and chewiness. Salt
reduction had a negative influence on bread volume, shape and flavour, but
positively effected crumb hardness, gumminess and chewiness.
Key words: transglutaminase, texture, whole meal wheat bread, salt reduction
INTRODUCTION
Gluten is a fundamental component for the overall quality and structure of breads.
In wheat the gliadins (prolamins) are responsible for dough’s cohesiveness, while
the glutenins (glutelins) are apparently responsible for the dough’s resistance to
extension. The combination of these two proteins, which results in the gluten
complex, confers the dough’s unique viscoelastic properties and the ability to retain
gasses, resulting in good quality breads [1]. Gluten rheological properties can be
altered by transglutaminase (TG) since it catalyses the formation of ε-(γ glutamyl-)lysine crosslinks in proteins via an acyl transfer reaction. Recent studies showed
that TG addition had a significant influence on dough and bread textural properties.
Basman et al. (2002) reported that TG addition at all levels generally resulted in
stronger dough properties, but superior handling properties were observed
especially at lower addition levels (less than 0.5 %) [2].
Nowadays, bakery industry is searching for ways to lower the concentrations of salt
added to bread products. Salt influences gluten behaviour, decreases yeast activity
in the dough, thus retarding gas production, and enhances bread flavour [3].
However, lowering the salt concentration usually results in inadequate dough
rheology and bread sensory properties [3].
The aim of this research was to determine the effect of TG addition on textural and
sensory properties of whole meal wheat bread and to see whether the addition of
TG could also make up for reduced salt addition.
MATERIALS AND METHODS
Materials
Whole meal wheat flour (Farina, Croatia) of ash content 1.9 % on dry matter basis
and moisture content 13.6 %, was used for dough preparation and bread making.
The flour was characterized by wet gluten content 18.8 %, farinograph water
absorption 64 %, and maximum viscosity 890 AU. Tap water, compressed yeast
(Kvasac d.o.o., Croatia), “Format improver” (Ireks Aroma, Croatia), salt (Solana
Pag, Croatia) and transglutaminase preparation Activa WM (Ajinomoto Europe,
Germany) with an activity of 100 U/g protein were also used for dough and bread
making.
Methods
1. Experimental plan
Experimental plan was made using central composite design by Design Expert
7.1.3 software (Stat-Ease Inc., USA) as showed in Table 1.
Table 1. Salt and transglutaminase concentrations in bread samples
Sample
0
1
2
3
4
5
6
7
8
9
NaCl concentration
(% w/w)
1.80
1.80
1.80
1.08
1.50
1.50
1.20
1.20
1.50
1.92
TG concentration
(g TG/100 g flour)
0.00
0.10
0.30
0.20
0.34
0.20
0.30
0.10
0.06
0.20
2. Dough rheology
Farinogram characteristics of the flours and dough containing different levels of
microbial transglutaminase and salt were determined using ICC approved method
[4]. Uni-axial extensibility of prepared dough samples was assesed by the Kieffer
dough and gluten extensibility rig manufactured by Stable Micro Systems for
TA.HDplus Texture Analyser. Resistance to extension (g) and extensibility (mm)
were determined in tension mode by recording the peak force and the distance at
the maximum and the extension limit [5].
3. Bread making
Control bread containing no TG was prepared by mixing whole meal wheat
flour (1600g), tap water (1024 g), compressed yeast (48 g), salt and improver (16
g). TG and salt were added according to experimental design shown in Table 1. All
ingredients were mixed in a spiral mixer (Diosna SP12, Germany) for 3 minutes at
90 rpm and 6 minutes at 180 rpm. After resting 10 minutes, bread dough was
divided into 70 g pieces, rounded, and placed in proofing cabinet at 30 °C / 95 %
RH for 85 minutes. Breads were baked at 190 °C for 15 minutes with 0.5 L steam
at start and cooled at room temperature for 60 min.
4. Selected bread quality parameters
Texture profile analysis in a double compression cycle was performed using
TA.HDplus Texture analyser with a cylindrical 25 mm probe, 25 kg load cell, 50%
penetration depth and a 30 s gap between compressions on two 12.5 mm thick
slices. Bread volume was determined by a rapeseed displacement method (AACC
Standard 10-05) and the ratio volume/mass (specific volume) was calculated. Bread
height and diameter was measured by a calliper and the shape (height/diameter)
was calculated [6]. Sensory characteristics of baked bread were assessed by a panel
of five experts.
RESULTS AND DISCUSSION
1. Dough rheology
Farinogram and textural properties of prepared dough samples are shown in
Table 2. Addition of TG had a significant (p < 0.05) influence on dough
consistency, showing a decrease in consistency with higher concentrations of added
TG. It also had an influence on dough softening (r=0.955), with dough being firmer
as the TG concentration increased. These results, especially for consistency can be
considered unexpected if we take into consideration the main purpose of TG, which
is to form dough which has better handling characteristics. It also had a significant
effect on dough extensibility and resistance to extensibility. Resistance to extension
highly correlated to TG concentration (r=0.901). It had an opposite effect on
extensibility with correlating coefficient r=-0.912. Extensibility decreased as TG
concentrations increased. The resistance to extension ratio (R/E) positively
correlated to increase of TG concentration (r=0.944). The similar results were
reported by Caballero et al. [7]. Addition of TG had no significant influence on
dough development time and stability.
Table 2. Farinogram and textural properties of prepared dough samples
Sample
Consistency
[FU]
Softening
[FU]
Development
time [min]
Stability
[min]
0
1
2
3
4
5
6
7
8
9
500
480
480
470
460
456.7
460
480
480
450
28
30
90
58
100
70
100
30
30
80
17
8
10
9.5
9
8.8
8.5
8.5
10.5
10
0
6
0
0
0
0
0
5.5
4.5
0
Resistance to
extensibility
(max) [g]
16.75±0.58
24.04±1.10
38.95±1.50
36.96±3.92
36.95±3.92
36.34±5.42
32.61±2,99
23.69±0.89
21.11±1.62
33.35±2.06
Extensibility
[mm]
20.31±1.94
16.61±0.56
13.46±0.57
13.79±0.96
13.79±0.96
14.66±0.97
11.90±1.23
16.19±1.14
17.24±1.31
14.02±0.73
2. Bread physical and sensorial properties
Effects of TG addition on specific volume, shape, resilience, springiness and
cohesiveness are shown in Figure 1. Specific volume significantly decreased as the
TG concentration increased (r=-0.923). The reason for this decrease in specific
volume is crosslinking of the gluten network to form a firmer grid. The particular
effect of TG on bread quality has been previously studied with contradictory
results, and it seems to be tied with different factors such as the quantity of water
used, the dose of TG [8], and the baking quality of flour [7]. Specific volume could
probably be increased by changing the dough making and baking procedure, e.g. by
adding more water. An effect of TG addition on bread shape was not significant but
should not be neglected (p=0.065), and we can say that TG addition improved
shape. Based on statistical analysis, samples containing higher concentrations of
salt and TG had better shape. This is in agreement with results by Caballero et al
(2007) who concluded that the addition of TG led to a significant increase in
height/weight ratio and a decrease in specific volume [7]. Bread resilience and
springiness were not significantly affected by TG addition. At the same time, salt
had a negative effect on crumb resilience (r=-0.650). TG addition had a negative
effect on bread cohesiveness (Figure 1).
Specific volume, shape, resilience,
springness, cohesiveness
SPECIFIC VOLUME
SHAPE
RESILIENCE
SPRINGINESS
COHESIVENESS
3
2.5
2
1.5
1
0.5
0
Sample
Figure 1. Specific volume, shape, resilience, springiness and cohesiveness of
bread samples
Increasing concentrations of TG led to a significant increase in bread hardness
(r=0.854), gumminess and chewiness (Figure 2). However, this increase is not
suitable for end user satisfaction. It is important to mention that both, salt and TG
effected crumb hardness increase. As already shown, both negatively effected
specific volume and significant correlation between bread volume and hardness
was found (r=-0.856). From these results, we can conclude that TG was the most
active during the proofing and initial baking phase, and not during the dough
mixing procedure. Upon the optimisation done using Design Expert software, as far
as bread physical properties are concerned, salt concentration can be lowered to 1.2
g/100 g flour with the addition of 0.12 g TG/100 g flour.
Hardness, gumminess and
chewiness
Hardness
Gumminess
Chewiness
2500
2000
1500
1000
500
0
Sample
Figure 2. Crumb hardness, gumminess and chewiness of bread samples
Sensory properties of bread samples are shown in Figures 3 and 4. Higher TG
concentrations had a negative impact on volume and taste, but it had no influence
on the outer appearance, crumb and crust appearance and odour. Lowered salt
concentrations had a negative effect on volume, odour, crumb and crust taste and
crumb appearance. Judging on the sensory panel results, the optimal concentration
of salt in bread was 1.8 g/100 g flour.
1,8 NaCl+0TG
1,8NaCl+0,3MTG
Flavour
1,8NaCl+0,1TG
1,5NaCl+0,34TG
Volume
5
4
3
2
1
0
1,08NaCl+0,2TG
Appearance
Crumb
appearance
Odour
Figure 3. Sensory properties of bread samples (samples 0-4)
1,2NaCl+0,3TG
1,5NaCl+0,06TG
1,5NaCl+0,2TG
1,92NaCl+0,2TG
1,2NaCl+0,1TG
Volume
Flavour
Odour
5
4
3
2
1
0
Appearance
Crumb
appearance
Figure 4. Sensory properties of bread samples (samples 5-9)
CONCLUSIONS
The aim of this research was to determine the effect of TG addition on dough
rheology and quality parameters of whole meal wheat bread and to see whether the
addition of TG could also make up for reduced salt addition. TG addition
significantly influenced dough consistency and extensibility, with dough
consistency and extensibility being lower as the TG concentration increased. Bread
specific volume significantly decreased as TG concentration increased, and crumb
hardness significantly increased as both TG and salt concentrations increased.
Optimal TG concentration for achieving desirable physical properties was 0.12 g
TG/ 100 g flour while reducing salt addition to 1.2 g/100 g flour in comparison to
1.8 g/100 g flour mainly used in bread making. However, based on sensory
analysis, the optimal salt concentration for production of whole meal wheat bread
was 1.8 g/100g flour.
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