PROCESS ENGINEERING ENERGY CONSUMPTION IN BREAD BAKING

Abstract

The main aim of the present work is to study and evaluate energy consumption in bread baking. This was achieved by determining the energy consumed in each stage of bread baking processing to assess the most consumable stage of bread baking process. Magr baladi, Mawi and French bread baking were evaluated processes. Thermal, electrical and human energy sources were determined. The results indicated that the total specific energy consumed were 3038.11, 2831.85 and 4823.53 kJ kg-1 for magr baladi bread, mawi baladi bread and French bread, respectively. The specific electrical energy consumed were 42.21, 40.33 and 59.92 kJ kg-1 for magr baladi bread, mawi baladi bread and French bread, respectively. The specific human energy consumed were 5.35, 5.42 and 10.72 kJ kg-1 for magr baladi bread, mawi baladi bread and French bread, respectively. The specific thermal energy consumed were 2990.50, 2786.10 and 4752.89 kJ kg-1 for magr baladi bread, mawi baladi bread and French bread, respectively, which represent 98.43, 98.38 and 98.54% of the total energy consumed. The Total costs of different types of bread baking were 2.32, 1.76 and 4.80 LE kg-1 for Magr baladi, Mawi baladi and French bread, respectively.

Full text

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The 20th Annual Conference of Misr Soc. of Ag. Eng., 12 December 2015.
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ENERGY CONSUMPTION IN BREAD BAKING
Islam F. El-Adly*, El-Sayed G. Khater**,
Adel H. Bahnasawy*** and Samir A. Ali***
ABSTRACT
The main aim of the present work is to study and evaluate energy
consumption in bread baking. This was achieved by determining the
energy consumed in each stage of bread baking processing to assess the
most consumable stage of bread baking process. Magr baladi, Mawi and
French bread baking were evaluated processes. Thermal, electrical and
human energy sources were determined. The results indicated that the
total specific energy consumed were 3038.11, 2831.85 and 4823.53 kJ kg-
1 for magr baladi bread, mawi baladi bread and French bread,
respectively. The specific electrical energy consumed were 42.21, 40.33
and 59.92 kJ kg-1 for magr baladi bread, mawi baladi bread and French
bread, respectively. The specific human energy consumed were 5.35, 5.42
and 10.72 kJ kg-1 for magr baladi bread, mawi baladi bread and French
bread, respectively. The specific thermal energy consumed were 2990.50,
2786.10 and 4752.89 kJ kg-1 for magr baladi bread, mawi baladi bread
and French bread, respectively, which represent 98.43, 98.38 and 98.54%
of the total energy consumed. The Total costs of different types of bread
baking were 2.32, 1.76 and 4.80 LE kg-1 for Magr baladi, Mawi baladi
and French bread, respectively.
Keywords: Thermal Energy, Electrical Energy, Human Energy, bread, baking
1. INTRODUCTION
nergy is one of the most important parameters in the
manufacturing industries. In most cases, energy cost outweighs
the costs of other resources such as raw material, labors,
depreciation and maintenance (Fadare, 2003). Scientific production and
analysis of energy consumption will be of great importance for the
planning of energy strategies and policies.
* Administrator of Agric. Eng. Dep., Fac. of Agric., Benha Univ., Egypt
** Lecturer. of Agric. Eng., Fac. of Agric., Benha Univ., Egypt
*** Professor. of Agric. Eng., Fac. of Agric., Benha Univ., Egypt
E
Agricultural Engineering and Country Challenges: 535 - 554

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Nowadays, energy usage in agriculture has been intensified in response to
continued growth of human population, tendency for an overall improved
standard of living and limited supply of arable land; thus, the farmers use
their inputs in excess and inefficiently, particularly when the inputs have
low price or are available in plenty. The enhancement of energy
efficiency not only helps in improving competitiveness through cost
reduction, also results in minimized energy-related environmental
pollution, thus positively contributing towards sustainable development
(Kizilaslan, 2009 and Ghorbani et al., 2010).
Bread production occurs on a number of different scales, from the artisan
bakeries serving the local community, to the large commercial bakeries
serving entire nations, as well as in-store supermarket bakeries, small
chain outlets and anything in between. Baking ovens come in a variety of
different configurations, from small domestic units to large tunnel ovens.
Industrial ovens are typically gas powered and are usually classified as
direct (forced convection), indirect, microwave, radiation, or infrared
systems (Keskin et al., 2004; Mirade et al., 2004; Sakin et al., 2009;
Khatir et al., 2012; Khater and Bahnasawy, 2014). Other energy
sources include oil, electricity and woodchip burners. Previous studies in
the baking industry estimate that the specific energy consumption of a
bread oven is typically anywhere between 0.5 and 7.3 MJ/kg production
(Le Bail et al., 2010).
Baking is an energy-intensive process due to water evaporation occurring
in the product (latent heat of water vaporization is 2.257 MJ kg-1 at 100
°C). The energy demand for a conventional baking process is around 3.7
MJ kg-1, though it can be higher (up to 7 MJ kg-1) depending on specific
products and operating conditions. In this sense, baking is similar to
(conventional) drying, both demanding a high amount of energy in
comparison with chilling, freezing, and canning, which need less than 1
MJ kg-1 (Le Bail et al., 2010).
There are approximately 18,000 baladi bakeries in Egypt. 90% are
privately owned and 10% are publicly owned. The public bakeries have
an average throughput of 7 tons of flour per day while the private bakeries
average 1 ton per day. Bakeries pay 160 LE t-1 for subsidised flour. Note

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that if the price of wheat was US$200 t-1, the unsubsidised price of flour
would be in excess of 1,100 LE t-1. The technology used in the bakeries
appears to be fairly uniform, with similar oven sizes and designs. The
Egyptian Government provides a range of subsidised goods and services
to the Egyptian people, including subsidised (baladi) bread. The Egyptian
Ministry of Finance estimates that approximately 12-13 billion LE is
spent per year on subsidising Baladi bread and flour, which equates to
roughly 1.5% of Gross Domestic Product (GDP) (World Bank, 2010).
There is no known report in the literature on the energy requirements of
bread baking as practiced in Egypt. Such information is vital so as to
enable the management of this industry to develop strategies for better
control of their production operations and modify areas of waste. It will
also enable the management to properly appraise their energy
consumption for effective planning of production network. The study will
provide an opportunity for having a reliable database concerning
consumption of some types of energy by different users in bread baking.
It will also provide a firm basis of identifying options for saving energy in
bread baking operations; therefore, the main aim of the present work is to
study and evaluate energy consumption of baking of different types of
breads. 2. MATERIALS AND METHODS
The main experiment was carried out at the three local bakeries ovens,
Moshtohor, Toukh, Kalubia Governorate, Egypt, during the period of
2015 season to evaluate of energy consumption in the baking of different
types of breads.
2.1. Bread baking ovens description:
The stages of the bread baking are: material receiving and ingredients
weighing, mixing, fermentation, dividing, molding, proofing, baking and
cooling. Magr baladi, Mawi baladi and French bread bakeries were
included in this study.
Magr baladi baking oven consists of kneading machine, dividing
machine, molding machine and baking oven. Kneading machine consists
of mixing ban, kneading machine and motor. It is driven by 4 hp motor
and having a gear box to control the speed of mixing depending on the

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load. The mixing ban capacity is 150 kg of flour. The dividing machine
dimensions are 1.7 m long, 1.0 m wide and 1.55 m high. Its capacity is
200 kg. It is driven by 2 hp motor and having a gear box to control the
speed.
The molding machine consists of two parts, each part consists of belt and
motor. The dimensions of belt in first part are 1.43 m long, 0.46 m wide
and 0.95 m high. The dimensions of belt in second part are 1.45 m long,
0.46 m wide and 0.79 m high. Each part is driven by 2 hp motor and
having a gear box to control the speed.
The oven baking consists of belt and motor with 60 loaves for capacity.
The belt is driven by 4 hp motor and having a gear box to control the
speed of baking depending on the load. The length of belt is 4 m with a
forward speed of 5.3 cm s-1. Figure (1) shows the stages of bread baking
in magr baladi bread.
Figure (1): Stages of baking in Magr baladi bread bakery.
Mawi baladi bread bakery which consists of kneading machine and oven
baking. Kneading machine similar to that of the Magr baladi oven. The
oven baking consists of belt and motor with 60 loaves capacity. The belt
is driven by 4hp motor and having a gear box to control the speed of
baking depending on the load. The length of belt is 3 m and the speed is
2.2 cm s-1. Figure (2) shows the stages of baking in mawi baladi bread.

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Figure (2): Stages of baking in Mawi baladi bread bakery.
French bread bakery consists of kneading machine and oven baking.
Kneading machine consists of mixing ban, kneading machine and motor.
It is driven by 2 hp motor and having a gear box to control the speed of
mixing depending on the load. The mixing ban capacity is 100 kg of
flour. The oven baking consists of 4 shelves. Dimensions of the oven are
2 m long, 1 m wide and 2 m high. The distance between shelves is 50cm.
Load of each shelf is 42 loaves (45 g loaf-1). Figure (3) shows the stages
of French bread bakery.
Figure (3): Stages of French bread bakery.
2.2. Measuring devices:
The power requirement (kW) was determined by recording the voltage
and current strength by using the clamp meter (Model DT266 - Measuring

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range 200/1000A and 750/1000V with an accuracy of ± 0.01, China) to
measure the line current strength (I) and the potential difference value
(V).
2.3. The specific energy consumption:
The total energy consumption (electrical, human and thermal) for each
component was calculated for the production of finished bread baking for
three oven types. The procedures were used:
Electrical energy consumption was estimated from the measured electric
current and voltage values and estimated according to Kurt (l979) as
follows:
(1)
Pro 1000 cos3




VI
Ep
Where:
Ep is the electrical energy, kJ kg-1
I is the electric current, Amperes.
η is the Mechanical efficiency assumed to be 0.95 (Metwally,
2010). Vis the electrical voltage, V
cosφ is the Power factor being equal to 0.84
Pro is the productivity, kg s-1
According to Odigboh (1997), at the maximum continuous energy
consumption rate of 0.30 kW and conversion efficiency of 25%, the
physical power output of a normal human labor in tropical climates is
approximately 0.075 kW sustained for an 8–10 h workday. This was
calculated mathematically as:
(2)
Pr
075.0 oN
Em
Where:
Em is the Human energy, kJ kg-1
N is the number of persons involved in an operation.
Machine productivity was determined by dividing product mass by time,
Mg h-1.
Thermal energy consumption was estimated from equation:

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(3)
Pro
hvm
ET


Where: Et is the thermal energy, kJ kg-1
m is the mass flow rate, kg s-1
hv is the heating value of disel, 42000 kJ kg-1 (Shahin et al.,
2008)
2.4. Total Costs:
Hourly cost is calculated according to the equation that is given by
Awady (1978) as follows:
 
(4)
k
m
ew
2
1





 rt
i
ah
p
C
Where:
C is the hourly cost, LE h-1
p is the price of the equipment, LE
h is the year by working hours, h
a is the life expected of the machine, year
i is the Interest rate, %
t is the taxes and over heads ratio, %
r is the repair and maintenance ratio, %
w is the power of motor in, kW
e is the electricity cost, LE kW-1 h-1
m is the operator monthly salary, LE.
k is the monthly average working hours.
Cost inputs are listed in table (1).

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Table (1): Cost inputs.
Items
Equipment
Kneading
machine
Dividing
machine
Molding
machine
Oven
baking
French oven
baking
Price of equipment, LE.
16000
11000
7000
24000
28000
Motor, kW
3.0
1.5
1.5
3.0
2.0
Life expected, year
10
Taxes, %
3
Repair, %
10
Interest, %
10
Labors, LE h-1
10
3. RESULTS AND DISCUSSIONS
3.1. Energy Consumed in bread baking oven:
- Magr baladi bread baking:
Table (2) shows the energy consumed in the Magr baladi bread baking
and figures (4 and 5) show the energy flow diagram and percentages of
energy consumption in the bread baking. It could be seen that, the total
energy consumed is divided into three types, namely, electrical, human
and thermal energies. The results indicated that the total energy consumed
was 3038.07 kJ kg-1. The electrical energy required for bread baking was
42.21 kJ kg-1 (1.39%), where, the human energy consumed was 5.35 kJ
kg-1 (0.18%). The results also indicate the thermal energy for bread
baking was 2990.50 kJ kg-1 which is considered the highest rate in the
consumption of total energy in the bread baking and represented 98.43%
of the total energy consumed in bread baking. These results agreed with
those obtained by Le Bail et al. (2010) whose found that the energy
consumption of a bread is typically anywhere between 0.5 and 7.3
MJ kg-1 production (500 and 7300 kJ kg-1). Mixing process consumed an

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electrical energy of 15.8 kJ kg-1 which represented 37.43% of total
electrical energy in whole process of baking (42.21 kJ kg-1).
The results also indicate that the specific energy consumed of raw
material receiving was 0.069 kJ kg-1 (0.002%). The specific energy
consumed of handling was 3.055 kJ kg-1 (0.10%). The specific energy
consumed of maxing was 16.057 kJ kg-1 (0.529%). The specific energy
consumed of dividing was 13.490 kJ kg-1 (0.444%). The specific energy
consumed of molding was 6.029 kJ kg-1 (0.198%). The specific energy
consumed of baking was 2998.45 kJ kg-1 which is considered the highest
rate in the consumption of total energy in the bread baking oven and
represented 98.695% of the total energy consumed in bread baking oven.
The specific energy consumed of packing was 0.958 kJ kg-1 (0.032%).
Table (2): The energy consumed in the Magr baladi bread baking.
Process
sequences
Process
Total energy consumed, kJ kg-1
Total
energy
consumptio
n, kJ kg-1
 of total
energy
consumption
Electrical
energy,
kJ kg-1
Human
energy,
kJ kg-1
Thermal
energy, kJ
kg-1
1
Raw material receiving
….
0.069
….
0.069
0.002
2
Handling 1 (to
kneading machine)
….
0.069
….
0.069
0.002
3
Mixing
15.812
0.245
….
16.057
0.529
4
Handling 2(to container
or troughs)
….
0.076
….
0.076
0.003
5
Fermentation
….
….
….
….
….
6
Handling 3(to fine bran
on wood slabs )
….
0.735
….
0.735
0.024
7
Dividing
13.490
….
….
13.490
0.444
8
Molding
6.029
….
….
6.029
0.198
9
Handling 4(to Proofing)
….
0.553
….
0.553
0.018
10
Proofing
….
….
….
….
….
11
Handling 5(to the
ovens)
….
0.627
….
0.627
0.021
12
Baking
6.883
1.026
2990.50
2998.45
98.695
13
Handling 6 (from the
belt)
….
0.801
….
0.801
0.026
14
Handling 7 (to cooling)
….
0.194
….
0.194
0.006
15
Cooling
….
….
….
….
….
16
Packing
….
0.958
….
0.958
0.032
17
Total
42.213
5.353
2990.50
3038.066
100
18
 of total energy
consumption
1.39
0.18
98.43
100
100

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Figure (4): Energy flow diagram of Magr baladi bread baking.

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Figure (5): The percentages of energy consumption Magr baladi bread
baking.
- Mawi baladi bread baking:
Table (3) shows the energy consumed in the Mawi baladi bread baking
and figures (6 and 7) show the energy flow diagram and percentages of
energy consumption in the bread baking. It could be seen that, the total
energy consumed is divided into three types, namely, electrical, human
and thermal energies. The results indicated that the total energy consumed
was 2831.851 kJ kg-1. The electrical energy required for bread baking was
40.33 kJ kg-1 (1.42%), where, the human energy consumed was 5.42 kJ
kg-1 (0.19%). The results also indicate the thermal energy for bread
baking was 2786.10 kJ kg-1 which is considered the highest rate in the
consumption of total energy in the bread baking oven and represented
98.38% of the total energy consumed in bread baking oven. These results
agreed with those obtained by Le Bail et al. (2010). Mixing process
consumed an electrical energy of 18.70 kJ kg-1 which represented 46.37%
of total electrical energy in whole process of baking (40.33 kJ kg-1).
The results also indicate that the specific energy consumed of raw
material receiving was 0.069 kJ kg-1 (0.002%). The specific energy
consumed of handling was 2.051 kJ kg-1 (0.063%). The specific energy
consumed of maxing was 18.917 kJ kg-1 (0.668%). The specific energy
consumed of dividing was 0.905 kJ kg-1 (0.0.032%). The specific energy
consumed of molding was 0.487 kJ kg-1 (0.017%). The specific energy
consumed of baking was 2808.611 kJ kg-1 which is considered the highest

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rate in the consumption of total energy in the bread baking oven and
represented 99.178% of the total energy consumed in bread baking oven.
The specific energy consumed of packing was 0.837 kJ kg-1 (0.030%).
Table (3): The energy consumed in the Mawi baladi bread baking.
Process
sequences
Process
Total energy consumed, kJ kg-1
Total energy
consumption
, kJ kg-1
 of total
energy
consumption
Electrical
energy, kJ
kg-1
Human
energy,
kJ kg-1
Thermal
energy,
kJ kg-1
1
Raw material receiving
….
0.069
….
0.069
0.002
2
Handling 1 (to
kneading machine)
….
0.061
….
0.061
0.002
3
Mixing
18.703
0.213
….
18.917
0.668
4
Handling 2(to
container or troughs)
….
0.067
….
0.067
0.002
5
Fermentation
….
….
….
….
….
6
Handling 3(to fine
bran on wood slabs )
….
0.010
….
0.010
0.001
7
Dividing
….
0.905
….
0.905
0.032
8
Molding
….
0.487
….
0.487
0.017
9
Handling 4(to
Proofing)
….
0.487
….
0.487
0.017
10
Proofing
….
….
….
….
….
11
Handling 5(to the
ovens)
….
0.553
….
0.553
0.020
12
Baking
21.63
0.857
2786.10
2808.61
99.178
13
Handling 6 (from the
belt)
….
0.70
….
0.70
0.025
14
Handling 7 (to cooling)
….
0.173
….
0.173
0.006
15
Cooling
….
….
….
….
….
16
Packing
….
0.837
….
0.837
0.030
17
Total
40.333
5.418
2786.10
2831.851
100
18
 of total energy
consumption
1.42
0.19
98.38
100
100

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Figure (6): Energy flow diagram of Mawi baladi bread baking.

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Figure (7): The percentages of energy consumption Mawi baladi bread
baking.
- French bread baking:
Table (4) shows the energy consumed in the French bread baking and
figures (8 and 9) show the energy flow diagram and percentages of
energy consumption in the bread baking. It could be seen that, the total
energy consumed is divided into three types, namely, electrical, human
and thermal energies. The results indicated that the total energy consumed
was 4823.529 kJ kg-1. The electrical energy required for bread baking was
59.917 kJ kg-1 (1.24%), where, the human energy consumed was 10.751
kJ kg-1 (0.22%). The results also indicate the thermal energy for bread
baking was 4752.892 kJ kg-1 which is considered the highest rate in the
consumption of total energy in the bread baking oven and represented
98.54% of the total energy consumed in bread baking oven.
Mixing process consumed an electrical energy of 34.42 kJ kg-1 which
represented 57.44% of total electrical energy in whole process of baking
(59.92 kJ kg-1).
The results also indicate that the specific energy consumed of raw
material receiving was 0.069 kJ kg-1 (0.001%). The specific energy
consumed of handling was 2.425 kJ kg-1 (0.051%). The specific energy

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consumed of maxing was 34.757 kJ kg-1 (0.721%). The specific energy
consumed of dividing was 3.889 kJ kg-1 (0.081%). The specific energy
consumed of molding was 2.608 kJ kg-1 (0.054%). The specific energy
consumed of baking was 4778.461 kJ kg-1 which is considered the highest
rate in the consumption of total energy in the bread baking oven and
represented 99.065% of the total energy consumed in bread baking oven.
The specific energy consumed of misting water was 1.32 kJ kg-1
(0.029%).
Table (4): The energy consumed in the French bread baking.
Process
sequences
Process
Total energy consumed, kJ kg-1
Total energy
consumption,
kJ kg-1
 of total
energy
consumption
Electrical
energy, kJ
kg-1
Human
energy,
kJ kg-1
Thermal
energy,
kJ kg-1
1
Raw material receiving
….
0.0688
….
0.0688
0.001
2
Handling 1 (to
kneading machine)
….
0.062
….
0.0623
0.001
3
Mixing
34.417
0.340
….
34.757
0.721
4
Handling 2(to table for
fermentation)
….
0.143
….
0.143
0.003
5
Fermentation
….
….
….
….
6
Dividing
….
3.889
3.889
0.081
7
Molding
….
2.608
….
2.608
0.054
8
Handling 3(to
fermentation room)
….
0.420
….
0.420
0.009
9
Proofing
….
….
….
….
10
Handling 4(to the
ovens)
….
0.420
….
0.420
0.009
11
Baking
25.50
0.069
4752.892
4778.461
99.065
12
Misting water
….
1.32
….
1.32
0.027
13
Handling 5 (to
Consumer)
….
1.38
….
1.38
0.029
14
Total
59.917
10.721
4752.892
4823.529
100
15
 of total energy
consumption
1.24
0.22
98.54
100

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Figure (8): Energy flow diagram of the French bread baking.
Figure (9): The percentages of energy consumption in the French bread baking.

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3.2. Comparison between the specific energy consumption of different
bread baking ovens types:
Table (5) and figure (10) show the specific energy consumed in different
bread baking bakeries. It could be seen that the specific energy consumed
in bread baking bakeries were 3038.11, 2831.85 and 4823.53 kJ kg-1 for
Magr, Mawi and French bread bakeries, respectively. The highest value
of energy consumed (4823.53 kJ kg-1) was found for French bread bakery,
while, the lowest value of energy consumed (2831.85 kJ kg-1) was found
for Mawi baladi bread bakery which is lower by about 2000 kJ kg-1 which
is due to the Mawi bread baking took less time to produced.
Table (5): Specific energy consumed in different types of bakeries.
Type of bakery
Specific energy consumed
Total energy
consumption,
kJ kg-1
Electrical
energy, kJ kg-1
Human energy,
kJ kg-1
Thermal
energy, kJ kg-1
Magr bread bakery
42.21
5.35
2990.50
3038.11
Mawi bread bakery
40.33
5.42
2786.10
2831.85
French bread bakery
59.92
10.72
4752.89
4823.53
Figure (10): Specific energy consumed in different types of bakeries.

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3.3. The total costs of different types of breads:
Figure (11) shows the estimated costs of different types of bread baking
bakeries. It could be seen that the total cost was 2.32 LE kg-1 for Magr
baladi bread oven as compared with 1.76 LE kg-1 for Mawi baladi bread,
while, the total costs for the French bread was much higher than that of
both Magr baladi and Mawi baladi ovens, where it recorded 4.80 LE kg-1.
It could be concluded that to produce one kg of French bread costed 2.07
and 2.73 times of that of Magr baladi bread and Mawi baladi bread,
respectively.
Figure (11): The total costs of different types of bread baking.
4. CONCLUSION
The experiment was carried out to evaluate energy consumption in
different types of bread baking. Three types of energy were used in bread
baking oven, namely, electrical, human and thermal energies. The thermal
energy represented the most energy consumed, where, it ranged from
98.38- 98.54% of the total energy consumed in bread baking. Human
energy ranged from 0.18 – 0.22% of the total energy consumed in bread
baking. Electrical energy ranged from 1.24 - 1.42% of the total energy
consumed in bread baking. The Total costs of different types of bread
baking were 2.32, 1.76 and 4.80 LE kg-1 for Magr baladi, Mawi baladi
and French breads, respectively.

PROCESS ENGINEERING
The 20th Annual Conference of Misr Soc. of Ag. Eng., 12 December 2015.
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