Journal of Cereal Science 25

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Journal of Cereal Science 25 (1997) 289301

Effects of Wheat Variety and Processing Conditionsin Experimental Bread Baking Studied by Univariate

and Multivariate Analyses

E. M. Magnus, E. Brathen, S. Sahlstrom, E. Mosleth Frgestad andM. R. Ellekjr

MATFORSKNorwegian Food Research Institute, Osloveien 1, N-1430 As, Norway, andAgricultural University of Norway, Department of Food Science, P.O. Box 5036, N-1430 As,

Norway

Received 15 December 1995

ABSTRACT

The effects of variety, mixing conditions and fermentation time on bread loaf characteristics werestudied by univariate and multivariate statistical methods. Nearly all the measured bread loafcharacteristics were significantly affected by variety, fermentation time, and mixing conditions.Significant interactions were also found. Multivariate analysis (principal component analysis; PCA),was used to find the main variation among the bread samples and to identify the bread loaf

characteristics that contributed to describe this variation. The characteristics loaf volume and weightdescribed a large part of the main variation among the loaves and these characteristics were studiedin more detail by response surface methodology. The loaf volume and weight response surfaces for

variet ies, which by multivariate analysis were found to have common properties, followed similargeneral patterns. It was shown that the experimental design used provided information about thebaking performance of wheat flours over a wide range of experimental conditions and, thus, can bea useful supplement to standardised and optimised baking tests. 1997 Academic Press Limited

Keywords: experimental baking, processing variables, univariate analysis, multivariate analysis.

tests have been developed and are routinely usedINTRODUCTIONin industry and research. In general, baking tests

It is well documented that wheat varieties diff

er can be classified as standard baking tests13 orwidely in their end-use properties, which is com- optimised baking tests3,4. The test baking pro-monly assessed by baking tests. Various baking cedure can also be designed to determine the

response of the flours to variations in the processingparameters, i.e. by response surface methodology.This technique has been applied to baking ex-

: PC = principal component;periments to study the effects of formulation5,6.

PCA = principal component analysis; SAS = statisticalBaking formula, mixing conditions and fer-analysis system; ICC = International Association for

mentation time can be varied in test baking pro-Cereal Science and Technology; AACC = Americancedures and appropriate levels of these factorsAssociation of Cereal Chemists; GRL = Grain Re-must be selected. Insufficient dough mixing, assearch Laboratory; ISO = International Associationwell as overmixing, have been documented asfor Standardization.

Corresponding author. having detrimental effects on bread loaf char-

07335210/97/030289+13 $25.00/0/jc960094 1997 Academic Press Limited


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E. M. Magnus et al.290

acteristics4,7,8. T h e effects of work input during from the Norwegian Grain Corporation, were usedmixing have also been studied using the GRL-200 in the study.experimental mixer7,8. The wheat samples were cleaned and tempered

The effect of fermentation time on bread loaf before milling on a laboratory mill (Brabendercharacteristics was studied by El-Dash1. Using a Quadrumat Senior, Model-No. 8802, Duisburg,straight grade flour from 50% hard Canadian Germany). Water absorption was determined bywheat and 50% Brazilian wheat, the loaf volume the Farinograph according to ISO Method 5530was found to increase with increasing fermentation 110. Wheat protein content was determined bytime (from 60 to 135 min), whereas external and Kjeldahl N determination (ICC Standard no. 105).internal characteristics of the bread loaves reachedan optimum at 105 min fermentation when asingle-stage fermentation procedure was used. Experimental designPreston et al.9 compared the baking response of

For each flour the rotatable central compositeflours from 33 hard wheat varieties to relate flourdesign11 shown in Figure 1 was adapted to minimisequality parameters to protein fractions by em-

the number of baking trials. Levels for each of theploying four diff

erent experimental baking pro- variables are shown in Table I. The centre pointcedures. Even though bread loaf attributes, i.e. loaffor each flour was baked three times and used forvolume, obtained by different baking proceduresestimation of error.were correlated, the relationships between baking

and protein parameters varied among the bakingprocedures. The results from the study by Prestonet al.9 show that the choice of experimental baking Experimental bakingprocedure can affect compositionfunctionality re-

A straight-dough method was used to bake breadlationships. In baking experiments it has beenloaves from 100 g dough. The formula was flourcommon to vary one factor at the time. However,(200 g, dry matter basis), dry yeast (3.6 g; Redunless variability in the processing factors is studiedSaf-Instant, S.I.L. Lesaffre, France) rehydrated insimultaneously, the interactions of the processingwater (84 mL) before use, and NaCl (2 g). Novariables cannot be determined.ascorbic acid or other flour additives were used.The objective of the present study was to de-Water addition according to the Farinogram ab-scribe the variability in characteristics of breadsorption was used. It should be noted that to obtainloaves from flours from different wheat varietiesequal dough consistency of the doughs from eachwhen mixing speed, work input during doughof the flours, variable amounts of water weremixing, and fermentation time were varied byadded, resulting in varying dough yield (Table II).means of an experimental baking procedure byThe doughs were mixed on a GRL-200 ex-which such responses could be observed.perimental mixer12 at 27 C. The mixer measuresUsing a rotatable central composite design,the energy used by the motor and records the workeffects of several factors could be studied by ainput (kJ/kg dry matter) during dough mixing. Theminimum number of baking trials. Univariate anddoughs were placed in a fermentation cabinetmultivariate statistical analyses and response sur-(Lillnord A/S, Odder, Denmark) at 27C and 70%face methodology were used to study the re-

RH. Mixing and fermentation conditions werelationships between processing parameters and varied (Table I). After fermentation, each doughbread loaf characteristics.was scaled into three 100 g pieces, rounded on therounding table of an Extensigraph (Brabender,

EXPERIMENTAL Duisburg, Germany), and placed on perforatedbaking trays. The trays were placed in a proofing

Wheat samplescabinet (Lillnord A/S, Odder, Denmark) and thedoughs fermented at 37C and 70% RH for 45Five varieties of Norwegian grown spring wheatsmin. The loaves were baked in a rotating hearth(Bastian, Tjalve, Reno, T7043, T8020) obtainedoven equipped with a fan (Bago-Line Type BEXfrom Agricultural University of Norway, De-1.0, Fjellebroen A/S, Faaborg, Denmark) for 20partment of Crop Science, two hard red springmin at 230C. Live steam was injected during thewheat varieties (Grandin and Katepwa) and one

hard red winter wheat variety (Haven) obtained first 35 s of baking.


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Univariate and multivariate analyses in experimental baking 291

8

13 4

514

15 1

7

9

10

6

312

11 2

25 95

130

70

23.4

52.2

Work input(kJ/kg dry matter)

Mixing

speed (rev/min)

Fermentation time (min)

Figure 1 Rotatable central composite design used for each wheat variety.

Table I Rotatable central composite design for each variety Table II Farinograph absorption and dough yield for thewheat flours

Sample Fermentation Mixing speed Work input

time Absorption, % Dough yielda

Sample (14% moisture (g/kg flour at 14%min rev/min kJ/kg drymatter basis) moisture

basis)1 120 100 3782 95 130 522 Bastian 596 1621

Tjalve 580 16053 95 130 2344 95 70 522 T8020 594 1619

T7043 604 16295 95 70 2346 60 150 378 Reno 596 1621

Haven 607 16327 60 100 6308a 60 100 378 Katepwa 684 1709

Grandin 636 16619 60 100 12610 60 50 378

aAll ingred ients inclu ded.11 25 130 522

12 25 130 23413 25 70 52214 25 70 23415 0 100 378

determined 2 h after baking according to AACCApproved Method 74-092 using a TA.XT2 Tex-a Central point repeated three times.ture Analyser (Stable Micro Systems, Surrey, Eng-land) fitted with a 35 mm diameter aluminiumplunger. The small bread loaf size necessitatedAnalyses of bread loaf characteristicsmodifications in the sampling procedure for tex-ture analysis. The top of the bread loaves wasAfter cooling to room temperature for 1 h, the

loaves were weighed, loaf volumes measured by a sliced off 25 cm from the bottom and resistanceto compression was measured on the bottom partrapeseed displacement method2, and loaf height

and width were measured. Crumb firmness was of the loaves. Crust and crumb colour were de-


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Table III Wheat protein content, extraction rate andtermined by a ChromaMeter CR-200 (Minolta,Farinograph absorption for the wheat samplesOsaka, Japan) and L = lightness, a = redness,

and b = yellowness were recorded. For each Protein content Extraction rateSample (d.m. basis) %loaf, four readings were taken and mean values

reported. In addition, loaf grain was scored ac-Bastian 153 702

cording to Dallmanns pore table13. Tjalve 144 728T8020 144 720T7043 130 708

Statistical analyses Reno 141 712Haven 148 735

Univariate analyses Katepwa 166 758Data from the baking experiments were analysed Grandin 160 726by analysis of variance (ANOVA) using the Gen-eral Linear Procedure of the Statistical AnalysisSystem version 602 (SAS Institute, NC 1989).Mean values for the three loaves obtained from Variability in each of the bread loaf propertieseach dough were used in the statistical analyses. Generally, the standard errors were relativelyThe effects of wheat variety, the processing vari-

small. Standard errors were calculated from theables, and their interactions on bread loaf char-observations in the centre point of the design (threeacteristics were tested.replications). Significant effects of wheat varietyand the three processing variables (fermentationMultivariate analysestime, mixing speed, and work input) on nearly allThe data were also subjected to Principal Com-bread loaf characteristics were found (Table IV).ponent Analysis (PCA; Mardia et al.14) usingThe F-values indicated that the bread loaf char-UNSCRAMBLER (CAMO A/S, Trondheim,acteristics were more dependent on variety andNorway), to find the main structures in the data.fermentation time than mixing speed and energyThe variables were weighted to equal varianceinput. As shown in Table IV, significant second-,and the model evaluated by crossvalidation15. Thethird-, and fourth-order interactions for many ofscores from PCA were subjected to ANOVA andthe bread loaf attributes were also found. TheTukeys Multiple Comparison Test (=005) tolarge number of statistically significant interactionsdetermine significant differences among the vari-showed that effects of one variable are dependenteties when considering all bread loaf characteristicson the levels of other variables. The high levelssimultaneously.of significance also showed highly reproducibleresults from the experimental baking.Response surfaces

The ranges and standard errors for all char-The effects of the processing parameters wereacteristics of the bread loaves from the differentstudied for each variety separately by a responsevarieties are shown in Table V. The loaf volumessurface method16. Quadratically smoothed surfacesranged from 175 to 360 mL/100 g dough. Theare presented.largest range in loaf volume within one varietywas found for Katepwa, followed by Bastian and

RESULTS T8020. Loaf height varied from 32 to 55 mm.Within the wheat varieties, the difference betweenProtein content, extraction rate, and waterthe highest and the lowest loaf ranged from 8 toabsorption of wheat flours22 mm. Loaf width varied from 89 to 127 mm andfor each wheat variety, the difference in loaf widthWheat protein content on dry matter basis varied

between 130% (T7043) and 166% (Katepwa) between the least and most wide bread loaf wasbetween 16 and 30 mm. Loaf weight varied from(Table III). Flour extraction rates for the di fferent

varieties were between 702 (Bastian) and 758% 704 to 814 g/100 g dough. Crumb firmnessvaried from 14 to 71 N. Generally, crumb firm-(Katepwa). Flour water absorption varied between

580 (Tjalve) and 684% (Katepwa). In general, ness values of loaves from Grandin and Havenwere low and showed little variation. Pore sizethe Norwegian samples had lower extraction rate

and water absorption levels than the North Amer- ranged from 45 to 80. Within each variety, thepore size of the bread loaves varied by 23 points,ican samples.


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TableIV

Sign

ificant

F-values

(P C (Haven and Grandin) and PC2 scores. These varieties were denoted


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A2 [Fig. 2(a)]. The remaining varieties were all add any information to these variables. Principalcomponents 37 contributed largely to the ex-significantly different from each other and from

the varieties in A2. In the plot of PC1 vs PC3 planation of the variance in crumb and crust

colour. These results showed that the colour at-scores [Fig. 2(b)], the A2 varieties were locatedrelatively close together on the right-hand side of tributes were complex and difficult to interpret.

This was also the case for pore size. Since vari-the plot. The varieties Tjalve and T7043 werealso located relatively close together in the PC1 ability in loaf properties related to size were mainly

explained by the first three principal components,vs PC3 score plot, whereas Reno had similar meanPC1 score but lower PC3 score than Tjalve and such properties were studied in more detail by

response surface methodology. Since loaf height,T7043. Grandin was located on the left-hand sidein the plot, and Haven between Grandin and loaf weight, and pore size were located relatively

close together in the loading plot [Fig. 2(e)], theseTjalve, T7043, and Reno. The plot of PC1 vsPC3 scores for the different fermentation times variables appear to express a common phe-

nomenon. From the loading plot it also can be[Fig. 2(d)] contained information similar to theplot of PC1 vs PC2 [Fig. 2(c)]. The PC1 scores of seen that loaf height was negatively correlated

with loaf width. Among these four bread loafthe fermentation times 0 and 60 min did notdiffer [Fig. 2(c)], whereas the PC1 scores for the characteristics, only one, loaf weight, was selectedfor further studies. From the location in the loadingremaining fermentation times differed from each

other and from those of 0 and 60 min. The similar plot [Fig. 2(e)], it can be seen that loaf volume wasnot correlated with other characteristics related toPC1 scores observed for samples given 0 and 60

min fermentation and the order of the PC1 score loaf size. Thus, loaf volume was also subjected tofurther studies by response surface methodology.for the different fermentation times (25 min < 60

min = 0 min < 95 min < 120 min) indicate non- The variability in loaf weight was mainly explainedby PC1 and 2 (93%, Table VI), whereas 73% oflinearity in the overall response to variation in

fermentation time. The PC2 scores for loaves from the variability in loaf volume were explained byPC1 and 2.doughs fermented for 0 and 25 min did not differ

from each other but from the scores of thosefermented for 60 min. Loaves from doughs fer-

Response surfacesmented for 95 and 120 did not differ in theirPC2 scores, but differed from those obtained from Response surfaces of the dependent variables were

estimated for all wheat varieties separately on thedoughs given shorter fermentation time. Theseresults were in agreement with the results obtained basis of the samples in the central composite design

(see Fig. 1). These response surfaces made it pos-by analysis of variance on the original set ofvariables. sible to study the sensitivity of the different wheat

varieties to changes in the processing conditionsThe loading plot for the bread loaf char-acteristics is shown in Figure 2(e) for PC1 vs PC2. (fermentation time, mixing speed, and work input).

A rather flat response surface indicates that theLoaves from Grandin located on the left side ofthe plot were characterised by large width, high wheat variety can tolerate variation in the pro-

cessing conditions without the bread loaf char-volume, and low weight. Similarly, loaves fromHaven were indicated to have highest volume acteristics being seriously affected, whereas a very

pointed surface indicate that the bread loaf char-and loaves from T7043 lowest volume. The A2-varieties were characterised by high loaf weight acteristics would be sensitive to the processing

conditions used. The response surfaces are pre-and height, and small width. Comparison of resultspresented in Figure 2(c) and (e) indicated that sented in Figures 3 and 4, and significant co-

efficients (


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1

20

4

00

1

40

1

60

1

80

2

00

2

20

2

40

2

60

2

80

3

00

3

20

3

40

3

60

3

80

Loafvolume(ml/100gdough)

Fer

men

tation

time

(min)

Mixin

gsp

eed(re

v/min)

120

60

100

80

0

20

40

60

80

100

120

BASTIAN

120

400

140

160

180

200

220

240

260

280

300

320

340

360

380


Fer

men

tation

time

(min)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

100

120

TJALVE

120

400

140

160

180

200

220

240

260

280

300

320

340

360

380


Fer

men

tation

tim

e(min)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

100

120

T8020

120

400

140

160

180

200

220

240

260

280

300

320

340

360

380


Fer

men

tationtime

(min)

Mixin

gsp

eed(re

v/min)

120

60

100

80

0

20

40

60

80

100

120

T7043

120

400

140

160

180

200

220

240

260

280

300

320

340

360

380


Fer

men

tation

time

(min)

Mixing

speed(re

v/min)

120

60

100

80

0

20

40

60

80

100

120

RENO

120

400

140

160

180

200

220

240

260

280

300

320

340

360

380


Fer

men

tation

time

(min)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

100

120

HAVEN

120

400

140

160

180

200

220

240

260

280

300

320

340

360

380


Fer

men

tation

time

(min)

Mixin

gsp

eed(re

v/min)

120

60

100

80

0

20

40

60

80

100

120

KATEPWA

120

400

140

160

180

200

220

240

260

280

300

320

340

360

380


Fer

men

tation

time

(min)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

100

120

GRANDIN

Figure3

Loa

fvo

lumeresponsesurfaces

fortheeightw

heatvarieties.

Responsesurfacesareshown

forwor

kinputleve

l378

kJ/kg

drymatter.


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65

85

70

75

Weight(g/100gdough)

Fer

men

tation

time

(min)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

10012

0

BASTIAN

80

65

85

70

75

Weight(g/100gdough)

Fer

men

tation

time(

min)

Mixin

gsp

eed(re

v/min)

120

60

100

80

0

20

40

60

80

10

0120

TJALVE

80

65

85

70

75

Weight(g/100gdough)

Fer

men

tation

ti

me

(min)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

100

120

T8020

80

65

85

70

75

Weight(g/100gdough)

Fer

men

tatio

ntime

(min)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

100

120

T7043

80

65

85

70

75

Weight(g/100gdough)

Fer

men

tation

time

(min)

Mixing

speed(re

v/min)

120

60

100

80

0

20

40

60

80

100

120

RENO

80

65

85

70

75

Weight(g/100gdough)

Fer

men

tation

time

(min

)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

1001

20

HAVEN

80

65

85

70

75

Weight(g/100gdough)

Fer

men

tation

time

(min)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

100

120

KATEPWA

80

65

85

70

75

Weight(g/100gdough)

Fer

men

tationt

ime

(min)

Mixin

gspe

ed(rev/m

in)

120

60

100

80

0

20

40

60

80

100

120

GRANDIN

80

Figure4

Loa

fweightresponsesurfaces

fortheeightw

heatvarieties.

Responsesurfacesareshown

forwor

kinputleve

l378

kJ/kg

drymatter.


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Table VII Significant (P


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Table VIII Significant (P


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6 Mettler, E., and Seibel, W. Effects of emulsifiers andconditions but also that the effect of fermentationhydrocolloids on whole wheat bread quality: A responsetime was dependent on the mixing conditions.surface methodology study. Cereal Chemistry 70 (1993)

Differences in susceptibility to variations in the 373377.baking process among bread loaves from different 7 Kilborn, R.H. and Tipples, K.H. Factors affecting mech-

anical dough development. I. Effect of mixing intensitywheat varieties will be related to the chemicaland work input. Cereal Chemistry 49 (1972) 3447.composition and structure of the flour components.

8 Kilborn, R.H. and Tipples, K.H. Factors affecting mech-Such work is currently in progress in our laborat-anical dough development. II. Implications of mixing at

ory. It is also likely that the response to various constant rate of energy input. Cereal Chemistry 49 (1972)processing conditions, i.e. the similar responses 4853.

9 Preston, K.R., Lukow, O.M. and Morgan, B. Analysis ofobserved for the varieties Bastian, T8020, andrelationships between flour quality properties and proteinKatepwa in this experiment, could be used tofractions in a world wheat collection. Cereal Chemistry 69

study the structurefunctionality relationships of(1992) 560567.

wheat varieties. 10 ISO. International Standards: ISO-5530-1: WheatflourPhysical characteristics of doughsPart 1: De-termination of water absorption and rheological prop-erties using a farinograph. ISO, Geneve, Switzerland.

11 Cochran, W.G. and Cox, G.M. Experiment design, 2ndREFERENCESed. John Wiley and Sons, New York (1971).

1 El-Dash, A.A. Standardization of mixing and fer- 12 Voisey, P.W. and Kilborn, R.H. An electronic recordingmentation procedure for experimental baking tests. Cereal GRL mixer. Cereal Chemistry 51 (1974) 841848.Chemistry 55 (1981) 436446. 13 Dallmann, H. Porentabelle. Verlag Moritz Schafer,

2 Kilborn, R.H. and Tipples, K.H. Canadian test baking Detmold, Germany (1981).procedures. I. GRL remix method and variations. Cereal 14 Mardia, K.V., Kent, J.T. and Bibby, J.M. MultivariateFoods World 26 (1981) 624628. analysis. Academic Press, London (1979).

3 American Association of Cereal Chemists. Method 1009, 15 Stone, M. Cross-validatory choice and assessment of stat-approved September 1985; Method 10-10B, approved istical prediction. Journal of Statistic Society 36 (1974) 111

January 1983, revised Septemb er 1985. AACC, St Paul, 147.Minnesota (1983). 16 Montgomery, D.C. Response Surface Methodology. In

4 Finney, K.F. An optimized, straight-dough, breadmaking Design and Analysis of Experiments, Chap. 15, Johnmethod after 44 years. Cereal Chemistry 61 (1984) 2027. Wiley and Sons, New York (1984).

5 Maningat, J.I., Wu, J.Y., Hoseney, R.C. and Ponte, J.G. 17 Box, G.E.P. and Draper, N.R. Empirical model building

Short-time breadmaking systems. A continuous mix sys- and response surfaces. John Wiley and Sons, New York(1987).tem. Journal of Food Science 53 (1988) 546548, 554.

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