THE EFFECT OF SALT, WATER AND TEMPERATURE ON WHEAT DOUGH RHEOLOGY

THE EFFECT OF SALT, WATER AND TEMPERATURE ON WHEATDOUGH RHEOLOGY

A. FARAHNAKY1,3 and S.E. HILL2

1Department of Food Science and TechnologySchool of Agriculture

Shiraz UniversityShiraz, Iran

2Food Sciences DivisionSchool of Biosciences

Sutton Bonington CampusUniversity of Nottingham

Loughborough, Leics, U.K.

Received for Publication August 9, 2006Accepted for Publication February 27, 2007

ABSTRACT

In this study the effect of salt, water and temperature on dough rheologywas modeled. Surface response methodology (D-Optimal mode) was used inorder to quantify and estimate any nonlinearity in the relationships betweenthe parameters under study. Each variable had five levels: salt (0, 1, 2, 3, 4%),water (50, 56, 62, 68, 74%), temperature (20, 25, 30 35, 40C). Temperature,added water and salt level all had significant effects on consistency, hydrationand total energy as measured by a farinograph. Addition of salt caused adecrease in consistency and total energy but increased the hydration time inparticular at low water levels. The effect of salt on hydration was related to itscompetition with flour in water absorption. The effect of added water onconsistency, hydration and total energy was negative. Added water softens thedough and decreases the hydration time and the energy required for mixing.Temperature increase had a negative effect on consistency, hydration time andtotal energy. Salt reduction affects the mixing process of the ingredients ofdough formulation. In total, the effect of salt was low compared with tempera-ture and added water. Using the models obtained and reported in this research,the effect of dough can be compensated by other parameters such as tempera-ture and added water level. The models presented in this article enable thereader to play with the parameters quantitatively.

3 Corresponding author. TEL.: 0098-711-2287029; FAX: 0098-711-6289017; EMAIL: [email protected]

Journal of Texture Studies 38 (2007) 499–510. All Rights Reserved.© 2007, The Author(s)Journal compilation © 2007, Blackwell Publishing

499

PRACTICAL APPLICATIONS

One of the ways of solving the technological problems of reduced-saltdough and bread is to change the temperature and added water level of wheatflour dough. Using the equations presented in this article, it is possible tocalculate the salt effect on consistency, hydration time and total energy of adough formulation at a known temperature and added water level, e.g., if thesalt level of a dough formulation changes from 2 to 1%, the changes requiredto other parameters (temperature and added water) to compensate the effect ofsalt can be obtained. This can have practical applications in the design ofbread-making equipments and in solving the technological problems of low-salt breads.

KEYWORDS

Added water, dough rheology, modeling, salt, temperature

INTRODUCTION

The main components of dough are wheat flour, water, salt and yeast. Theproduction of wheat dough is a process in which raw materials are mixed andsubjected to a large range of strain. Salt is added to develop flavor in the finalproduct, i.e., bread. It also toughens the gluten and gives a less sticky (moremachineable) dough. Salt slows down the rate of fermentation, and its additionis sometimes delayed until the dough has been partly fermented. The quantityused is usually 1.8–2.1% on flour basis, giving a concentration of 1.1–1.4% ofsalt in the bread. Salt is added either as an aqueous solution or a dry powder(Kent and Evers 1994). Salt also affects the brown color of breads. In absenceof salt the bread will be whiter.

Because of concerns over health-related issues regarding high intake of saltby consumers, the reduction of salt in different food products has recentlybecome the focus of many research projects, conferences and workshops. Saltreduction in processed foods is a major challenge for the industry that is underincreasing pressure from consumers, health professionals and regulatorybodies.

Bread, as one of the main sources of energy in the human diet, isresponsible for the majority of salt taken by each person daily. Therefore, toreduce the high uptake of salt, bread is one of the major products that needsmore attention. One of the main problems in the reduction of salt in bread isthe technological problems it causes in dough rheology and dough handling in

500 A. FARAHNAKY and S.E. HILL

the bread-making process, resulting in poor-quality breads in terms of texture,volume, flavor and color.

Kojima et al. (1995) investigated the addition of salt to the flour andreported that salt markedly affected the physical characteristics of the dough,especially at a 1.5% level. Two notable changes were the 1.4% decrease inwater absorption and a 2-min increase in the development time of the dough.

Farinograph studies showed that a combination of organic acids isolatedfrom San Francisco sourdough and NaCl affected dough properties. Mixingtime and stability of dough were greatly decreased when organic acids alonewere added. Salt had the opposite effect however; it increased mixing time anddough stability. Combinations of organic acids plus 1.5% NaCl increasedmixing time and dough stability. The original mixing profile of flour could berestored by decreasing the level of NaCl from 1.5 to 1.0%, or by adding 40- to80-ppm cysteine-HCl (Tanaka et al. 1967). Studies on the elastic and viscousmoduli of dough by Larsson (2002) showed that NaCl at concentrations up to2% (0.5, 1 and 2) increased the elastic modulus of wheat flour dough asmeasured by Bohlin CVO. Doughs with NaCl had greater strength than thosewithout. The effect of dough was related to gluten.

Harinder and Bains (1990) reported that salt increases the mixing toler-ance of dough, but decreases the consistency. When salt content was increasedfrom 0.0 to 2.5%, the dough development times increased by 35.0 and 33.3%,respectively. Salovaara (1982) in his study concluded that salt increases themachineability of dough. When salt was added to dough the protein associa-tion was increased, decreasing water absorption. Ionic, hydrophobic andhydrogen bonds were thought to be involved in this phenomenon.

The action of NaCl on dough was evaluated by flow behavior of thedough under defined conditions, by the dependence of dough viscosity onconsistency or by calculating a complex exponential relation between thevariables. The addition of NaCl increased dough consistency. The stabilizingeffect of NaCl was partially compensated by changes in protein composition,especially gliadin, during dough kneading (Hruskova and Hampel 1982).

One of the ways of solving the technological problems of reduced saltdough and bread is to change other production parameters. Therefore, it isnecessary to rationalize the effects of the main parameters of dough rheology– water content, temperature and salt – and determine the extent of importanceof each parameter. To our best knowledge to date, there is no research reportto enable the reader to quantify the effect of main technological parameterson dough rheology. The purpose of this study was to evaluate and quantifythe effects of salt, added water and temperature on the main parametersdetermining the rheology of dough to provide an alternative to compensate thenegative effects of reduction of salt with other parameters (temperature andwater content).

501WHEAT DOUGH RHEOLOGY

MATERIALS AND METHODS

Strong bread wheat flour (Viking wheat flour, U.K.) was used. No addi-tive was used in dough formulation except sodium chloride to keep the for-mulation as plain as possible. All chemicals used in this research were ofanalytical grade unless otherwise mentioned. The flour used was Viking flourwith moisture content of 14%. Software of Design-Expert 6.0.2: D-OptimalResponse Surface mode (Estate-Ease, Inc., Minneapolis, MN) was used inorder to model and estimate any nonlinearity in the relationships between theparameters under study. In total, 53 runs of different combinations of the threevariables were carried out. Each variable had five levels as follows:

1. salt (0, 1, 2 ,3, 4 %) (flour basis);2. water (50, 56, 62, 68, 74%) (flour basis);3. temperature (20, 25, 30 35, 40C).

Wheat dough is normally tested using standardized empirical equipmentsand procedures. In this research the rheological properties of dough withdifferent levels of salt and added water content at a range of temperatures wasmeasured using a doughLAB equipment (Newport Scientific Pty. Limited,Warriewood, Australia) connected to a farinograph standard mixing bowl. Thisequipment has been designed to measure the resistance a dough offers tokneading under different conditions of temperature, mixing speed and mois-ture content. The dough is developed in the mixing bowl by the rotary actionof two sigma-arm mixing blades and its resistance to kneading as a torquevalue is obtained. The time it takes for a dough to reach the peak resistance wasreported as the hydration time. The total amount of mechanical energy appliedto each dough during the dough preparation is reported as total energy.

The data obtained from the doughLAB was transferred to a PC using aninterface and analyzed using a software called DoughMAP (Newport Scien-tific Pty. Limited) supplied by the manufacturer and the required parameterswere extracted. The resultant data were analyzed using the Design-Expert6.0.2 and the best models were obtained. All variables and their interactionswith a significant effect in each model were kept and any variable or interac-tion without a significant effect was removed as performed using the software.

RESULTS

Effect of Salt, Added Water and Temperature on Dough Consistency

Consistency of each dough was obtained from its corresponding farino-graph curve in farinograph units (FU). The consistency of a dough obtainedusing a farinograph is a good indication of viscosity. However, doughs with the


same consistency can have different viscosities and can behave differently increep tests and in sensory assessments (Launay 1979). The effect of water andtemperature on dough consistency at 20 min is presented in Fig. 1. As seen, anincrease in added water or temperature decreases the consistency of dough.Figure 2 shows the effect of salt and added water on dough consistency at20 min. Increase of added water from 50 to 74% and salt from 0 to 4% causeda considerable reduction in the consistency of dough under the conditionstested.

Model of the Effect of Salt, Water and Temperature on DoughConsistency at 20 Min

Equation (1) is the model obtained using the Design Expert software torelate salt, temperature and added water to consistency of the dough at 20C interms of actual factors. If the actual values of the three parameters are put inEq. (1), an estimate of the consistency of the dough can be obtained:

C S T AW T AW= + − ⋅ − ⋅ − ⋅ + ⋅ ⋅3 964 29 20 39 60 44 49 41 0 75, . . . . . (1)

where C = consistency (FU), S = salt (%), T = temperature (C) andAW = added water (%).

65

297.5

530

762.5

995

20

25

30

35

40

50

56

62

68

74 Temperature (C)

Added water (%)

Con

sist

ency

(F

U)

FIG. 1. THE EFFECT OF ADDED WATER AND TEMPERATURE ON WHEAT FLOURDOUGH CONSISTENCY (FARINOGRAPH UNIT, FU) AT 20 MIN

The contour plot shown at the bottom indicates combinations of temperature and added watervalues with the same consistency level on each line.


Equation (2) is the model obtained using the Design Expert software torelate salt, temperature and added water to the consistency of the dough at 20Cin terms of coded factors. For each parameter, we have five levels withdifferent codes (actual levels and codes for each variable are given in Table 1).If the coded values of the three parameters of each treatment are placed inEq. (2), the estimated consistency of the dough under those conditions can beobtained.

50

287.5

525

762.5

1000

50

56

62

68

74

0

1

2

3

4

Added water (%)

Salt (%)

Con

sist

ency

(F

U)

FIG. 2. THE EFFECT OF SALT AND ADDED WATER ON WHEAT FLOUR DOUGHCONSISTENCY (FARINOGRAPH UNIT, FU) AT 20 MIN

The contour plot shown at the bottom indicates combinations of salt level and added water valueswith the same consistency level on each line.

TABLE 1.CODED VALUES OF SALT, ADDED WATER

AND TEMPERATURE FOR EACH LEVEL IN WHEATFLOUR DOUGH

Variable level 1 2 3 4 5

Code -1 -0.5 3 0.5 1Salt (%) 0 1 2 3 4Added water (%) 50 56 62 68 74Temperature (C) 20 25 30 35 40


In brief, the increase of all variables (salt, temperature and water level)will cause a reduction in the consistency of dough. As a rough estimation (ifwe ignore the interaction effects) then:

If the salt effect equals X then the temperature effect will be 3.5 times thatof salt and the added water effect will be eight times that of salt:

C S T AW T AW= + − ⋅ − ⋅ − ⋅ + ⋅ ⋅436 67 40 77 141 06 323 91 86 69. . . . . (2)

where C = consistency (FU) at 20 min, S = salt (%), T = temperature (C) andAW = added water (%).

Effect of Salt, Water and Temperature on Hydration Time of Dough

On the farinograph graph (consistency curve) of each dough, the timetaken to reach the maximum consistency was used as an indication of hydra-tion (Bloksma and Bushuk 1988). At this point the water added to the flour hasbeen absorbed by the flour but the network of the dough has not yet developedproperly.

The effect of added water and temperature on hydration time is presentedin Fig. 3. It reveals that at lower limits of temperature and added water (20C

0.5

1.8

3.0

4.3

5.5

2025

3035

40

50

56

62

68

74

Added water (%)Added water (%)

0.5

1.8

3.0

4.3

5.5

2025

3035

40

50

56

62

68

74

0.5

1.8

3.0

4.3

5.5

2025

3035

40

50

56

62

68

74

Added water (%)

Temperature (C )

Peak

tim

e (h

ydra

tion

time)

(m

in)

FIG. 3. THE EFFECT OF ADDED WATER AND TEMPERATURE ON HYDRATION TIME(MIN) OF WHEAT FLOUR DOUGH

The contour plot shown at the bottom indicates combinations of temperature and added watervalues with the same peak time on each line.


and 50%) the effect of the variables is much greater than at the higher limits(74% and 40C). In general, increase in temperature and added water both hadnegative effect on hydration time. However, limited effect of salt level onhydration is seen in Fig. 4. For actual factors

HT S T AW S TS AW

= + ⋅ − ⋅ − ⋅ − ⋅ ⋅ ⋅−⋅ ⋅ + ⋅

21.11 1.83 0.52 0.27 0.020.02 0.0073 TT AW⋅

(3)

where HT = hydration time (peak time, min), S = salt (%), T = temperature (C)and AW = added water (%), and for coded factors

HT S T AW S TS AW T

= + + ⋅ − ⋅ − ⋅ − ⋅ ⋅ ⋅−⋅ ⋅ + ⋅ ⋅

2.16 0.11 1.01 1.16 0.340.49 0.88 AAW

(4)

where HT = hydration time (peak time, min), S = salt (%), T = temperature (C)and AW = added water (%).

In terms of the effect on hydration time, salt level showed a minor effectcompared with added water and temperature. The extent of the effect ofthe three variables is in the order of: water > temperature > salt. Water and

740.00

50

0.5

2.0

3.5

5.0

6.5

1.00

2.00

3.00

4.0056

62

68

Salt (%)

Peak

tim

e (h

ydra

tion

time)

(m

in)

Added water (%)

FIG. 4. THE EFFECT OF ADDED WATER AND SALT ON HYDRATION TIME DURINGDEVELOPMENT OF WHEAT FLOUR DOUGH

The contour plot shown at the bottom indicates combinations of salt level and added water valueswith the same peak time on each line.


temperature had positive but salt had negative effect. When more water ispresent in the system, the consistency of the dough reduces markedly and thiswill ease the process of mixing and absorption of water. The same reason canbe applied to higher temperatures plus higher mobility and greater diffusioncoefficients of molecules.

Effect of Salt, Temperature and Water on Total Energy

The model of the effect of added water, temperature and salt on totalenergy (Figs. 5 and 6) for actual factors is

TE S T AW S TS AW T

= + − ⋅ − ⋅ − ⋅ + ⋅ ⋅ +⋅ ⋅ + ⋅

251 53 8.56 3 45 3 25 0 020.10 0.04

. . . .⋅⋅ AW

(5)

where TE = total energy, S = salt (%), T = temperature (C) and AW = addedwater(%), and for coded factors

TE S T AW S TAW T

= + − ⋅ − ⋅ − ⋅ + ⋅ ⋅ +⋅ ⋅ + ⋅

24 08 3 12 7 21 20 91 0 432 46 5 21

. . . . .. .S ⋅⋅ AW

(6)

0

15

30

45

60

20

25

30

35

40

50

56

62

68

74

0

15

30

45

60

20

25

30

35

40

50

56

62

68

74

0

15

30

45

60

20

25

30

35

40

50

56

62

68

74

Temperature (C)

Tot

al e

nerg

y (W

/kg)

Added water (%)

FIG. 5. THE EFFECT OF ADDED WATER AND TEMPERATURE ON TOTAL ENERGY (W/kg)APPLIED FOR WHEAT FLOUR DOUGH DEVELOPMENT

The contour plot shown at the bottom indicates combinations of temperature and added watervalues with the same applied energy level on each line.


where TE = total energy, S = salt (%), T = temperature (C) and AW = addedwater (%).

Using the coded values in Table 1, the total energy of dough making canbe estimated by placing the coded values of each sample in the Eq. (6).

Increase of all variables (salt, temperature and water level) will cause adecrease in total energy of dough production as measured by the doughLAB ina farinograph bowl.

As a rough estimation, if salt effect is taken as X, then temperature effectwill be about 2.3 times that of X, and added water effect will be 6.7 times thatof X.

To test the models obtained in this study (using a strong wheat flour),doughs with known formulations and conditions in terms of added water andsalt level and temperature were prepared in a farinograph. The model was ableto predict the consistency, hydration time and total energy of the dough and thedifference between the predicted and actual values was less than 3%.

DISCUSSION

The effect of the three main parameters, i.e., temperature, added waterand salt level, on dough mixing and production were studied using a standard

0

12.5

25

37.5

50

01

23

4

50

56

62

68

74Salt (%)

Tot

al e

nerg

y (W

/kg)

Added water (%)

FIG. 6. THE EFFECT OF SALT AND ADDED WATER ON TOTAL ENERGY (W/kg) APPLIEDFOR WHEAT FLOUR DOUGH PRODUCTION IN FARINOGRAPH MIXING BOWL

The contour plot shown at the bottom indicates combinations of salt level and added water valueswith the same applied energy level on each line.


mixing bowl under controlled conditions. The data obtained were used tomodel the effects. The software used was able to show the nonlinearity inrelationships between the variables and consistency, hydration time and totalenergy if present. Temperature, added water and salt level all had significanteffects on consistency, hydration and total energy. The addition of salt causeda decrease in consistency and total energy but increased the hydration time inparticular at low water levels. The effect of salt on hydration can be related toits competition in absorption of water with the flour. The effect of added wateron consistency, hydration and total energy was negative. Added water softensthe dough and decreases the hydration time and the energy required formixing. Temperature increase had negative effect on consistency, hydrationtime and total energy.

The effect of salt is thought to be a result of the changes in glutenhydration and the actions that can free and bind water as reported by Galalet al. (1978). When salt is present in the system, it is thought to increase theamount of free and mobile water in the system by altering the gluten structurein a way that salt occupies the sites once occupied by the bound water.

CONCLUSION

Salt reduction affects the mixing process of the ingredient of doughformulation. In total, the effect of salt was low compared with temperature andadded water. It also affects the rheology of the final dough. Using the modelsobtained and reported in this research, the effect of dough can be compensatedby other parameters such as temperature and added water level. Little changein temperature and added water level can compensate for the effect of saltreduction on dough consistency. The models presented in this article enablethe reader to play with the parameters quantitatively.

REFERENCES

BLOKSMA, A.H. and BUSHUK, W. 1988. Rheology and chemistry of dough.In Wheat: Chemistry and Technology (Y. Pomeranz, ed.) pp. 131–216,American Association of Cereal Chemists, Inc., St. Paul, MN.

GALAL, A.M., VARRIANO-MARSTON, E., JOHNSON, J.A. andCHEMISTRY, C. 1978. Rheological dough properties as affected byorganic acids and salt. Cereal Chem. 55, 683–691.

HARINDER, K. and BAINS, G.S. 1990. High alpha-amylase flours – effect ofpH, acid, and salt on the rheological properties of dough. Cereal Chem.67, 588–594.


HRUSKOVA, M. and HAMPEL, J. 1982. Effect of sodium chloride on tech-nological properties of doughs. Food Feed Chem. 53, 163–190.

KENT, N.L. and EVERS, A.D. 1994. Technology of Cereals: An Introductionfor Students of Food Science and Agriculture. Pergamon Press, Oxford,U.K.

KOJIMA, M., TOGAWA, T., MURASE, M., TOTANI, S., SUGIMOTO, M.and KAISHI, N.S. 1995. Effects of addition of water and sodium chlorideon microstructure and rheological properties of noodles. Food FeedChem. 42, 899–906.

LARSSON, H. 2002. Effect of pH and sodium chloride on wheat flour doughproperties: Ultracentrifugation and rheological measurements. CerealChem. 79, 544–545.

LAUNAY, B. 1979. Proprietes rheologiques pates de farine quelques progresrecents. Ind. Alimnt. Agric. 96, 617–623.

SALOVAARA, H. 1982. Effect of partial sodium-chloride replacement byother salts on wheat dough rheology and breadmaking. Cereal Chem. 59,422–426.

TANAKA, K., FURUKAW, K., MATSUMOTO, H. and CHEMISTRY, C.1967. Effect of acid and salt on the farinogram and extensigram of dough.Cereal Chem. 44, 675–680.


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THE EFFECT OF SALT, WATER AND TEMPERATURE ON WHEAT DOUGH RHEOLOGY