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Roll-in shortenings effects on Danish pastries sensory properties studied by principal component analysis
Lebensm.-Wiss. u.-Technol., 28, 72-77 (1995)
Roll-in Shortenings Effects on Danish Pastries Sensory Properties Studied by Principal Component Analysis Pernille Baardseth, Tormod Naes and Gjermund Vogt Norwegian Food Research Institute, MATFORSK, Osloveien 1, N-1430/ks (Norway) (Received March 29.1994: accepted August 17. 1994)
The effects of I1 different shortenings, either made of milk fat or vegetable oil. at three concentrations (350. 500 and 600 g/kg) opt sensoo' properties, and instrumental texture and colour of Danish pastries were investigated. Principal component analysis (PCA) revealed m,o dominating components for sensory properties; the first to shortening type and the second to shortening concentration. Results were verified by analysis of variance (ANO VA). Texture and colour were measured to verif3, the senso O, results and analysed by the same statistical methods using PCA and ANOVA. re.spectively.
Introduction Danish pastry is made from a rich yeast dough which has been layered with shortening by repeated folding and rolling steps in a process somewhat similar to that used for making puff pastry. The result is a silky tender crumb of characteristic appearance and a glossy flaky crust. The flakiness depends on the formation of thin films of gluten protein which trap water vapour and carbon dioxide from fermentation. Thus gluten films must be separated by continuous layers of fat in order not to form a three-dimensional structure. The sheets of fat act as a barrier preventing adjacent dough layers from fusing together while they are being reduced in thickness during the folding and rolling process. The main demands of Danish pastry roll-in shortening are therefore good spreadability and a plastic range extending to 10°C so that it does not become brittle when cooled and rupture the layering. Butter, margarine or specially fabricated vegetable oil shortenings can be used for the roll-in material (1, 2). Milk fat has to be fractionated to achieve these rheological properties (3). Sensory quality of a food commodity consists of several characteristics. Principal component analysis (PCA) is a useful technique for studying interdependencies and underlying dimensions of such characteristics. Baardseth et al. (4) used this technique to study the effects of dairy ingredients on the sensory properties of sausages. PCA revealed three dominating factors for sensory analysis. The results were verified by analysis of variance (ANOVA). The results of the sensory analysis were further verified by instrumental texture and colour analysis using PCA and ANOVA, respectively. These techniques prove to be useful in product development. The purpose of the present study was to demonstrate the usefulness of PCA to assess the influence of 11 roll-in shortenings made of milk fat or vegetable oil on important sensory characteristics of Danish pastries. For comparison, the data were also analysed by ANOVA. The 11 shortenings
were each used at three concentrations and the final products evaluated by descriptive sensory analysis. To verify the sensory results, colour and texture were determined instrumentally, the results being analysed by the same statistical methods.
Materials and Methods Dough preparation and processing
Wheat flour (570g/kg), water (213g/kg), fresh eggs ( 106 g/kg), sugar (43 g/kg), yeast (43 g/kg), skim-milk powder (21 g/kg) and salt (4g/kg) were used to make a dough batch. Eleven shortenings (Table 1), tempered at 18 °C for 7 d, were folded into the flat dough at three concentrations (350, 500 or 600 g/kg) to make a total of 33 doughs. The dough was kneaded with a Diosna kneading arm mixer (SP 40 D.U. S6hne, Osnabriick, Germany) for l l0s at 90rpm. The temperature of the water (2 °C), liquid mixture (6 °C), flour ( - 15 °C) and dough (6 °C) were recorded. The rolling and folding process occurred in four stages using a roller (Rollfix, A. Fritsch K.G. Markt Einersheim, Germany). The stages comprised sequential rollings to defined thicknesses, folding and one or more rollings followed by a rest period at 5 °C under plastic for 30 min (between stage I and 2 and stage 2 and 3) or 60min (between stage 3 and 4). Stage 1: roll to (mm) 30, 25, 20, 17.5, 15, 12.5; fold; roll to 30mm; rest 30min. Stage 2: roll to (mm) 25, 20, 17.5, 15, 12.5; fold; roll to 30 mm; rest 30 min. Stage 3: roll to (mm) 25, 20, 17.5, 15, 12.5, 10; fold; roll to (mm) 25, 20, 17.5, 15; rest 60 min. Stage 4: roll to (mm) 12.5, 10, 8.5, 7, 6, 5, 4, 3.5. The dough was cut into I0 x 10cm pieces, and stored uncovered at 5 °C until the next day. The dough pieces were proofed at 35 °C and 65% relative humidity for 65 min and baked in an oven (Bago-Line, Bex 1.0, Vester Aby, Denmark) at 220°C for 10.5min. The Danish pastries were cooled at room temperature (about 22°C) for l h before analysis. The productions were randomized.
0023-6438/95/010072 + 06 $08.00/0 (~) 1995 Academic Press Limited
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Table 1 Identification number and description of shortenings used in Danish pastries Shortening no.
10 I1
Shortening type Pure anhydrous Norwegian milk fat, plasticized, melting point 38 °C 800g/kg Norwegian milk fat fraction, plasticized, skim-milk powder, salt and lactic acid were added to the water phase, melting point 38 °C 980g/kg Norwegian milk fat fraction, plasticized, emulsifier and soya lecithin were added, melting point 38 °C 800g/kg Norwegian milk fat fraction, plasticized, skim milk powder, salt and lactic acid were added to the water phase, emulsifier and soya lecithin were added to the fat phase, melting point 38 °C Idun Rullemargarin. Luxuswiener; a commercial Norwegian roll-in shortening consisting of partially hydrogenated vegetable oil, water, salt, emulsifier and citric acid, melting point 37 °C Croissant, French milk fat fraction, plasticized, melting point 40°C MD-Foods, Danish milk fat fraction, plasticized, melting point 42 °C Veba Rullemargarin, a commercial Norwegian rollin shortening consisting of hydrogenated vegetable oil, vegetable oil, hydrogenated fish oil, water, skimmilk powder, salt, lecithin and emulsifier, melting point 39 °C Veba Puffmargarin. a commercial Norwegian roll-in shortening consisting of hydrogenated fish oil, vegetable oil, water, skim-milk powder, salt, lecithin and emulsifier, melting point 41 °C BBB-Wienervare, a commercial Norwegian roll-in shortening consisting of vegetable oil, water, salt, emulsifier and sodium citrate, melting point 39 °C Pals Wienervare, a commercial Norwegian roll-in shortening consisting of hydrogenated fish oil, vegetable oil, water, salt, emulsifier and lactic acid, melting point 39 °C
Sensory evaluation The sensory analysis was performed according to a descriptive sensory strategy. The sensory panel consisted of 10 trained panellists, and a continuous non-structured scale was used for evaluation. The left side of the scale, corresponding to the lowest intensity of each attribute, was given a value of 1.0 and the right side, corresponding to the highest intensity, was given a value of 9.0 (Senstec, Tecator, Htigan~is, Sweden). The properties evaluated were crust glossiness, whiteness, colour hue, colour strength, sponginess (vs. flakiness), butter odour, oil odour, butter taste, oil taste, saltiness, rancidity, crispness, juiciness, firmness, after-taste, mouth coating from fat. The paneilists were trained for the sensory characteristics of the product before the main trial, but they were not informed about the purpose of the experiment. Each panellist was given one Danish pastry at a time in random order and told to cut it into two with a knife to judge the flake structure and colour. No replicates were performed.
Instrumental textural analysis Firmness of the Danish pastries was determined by compression using a Kramer shear cell according to Blakeney (5), on an Instron Testing Instrument, model 4202 (Instron Ltd, High Wycombe, U.K.). The average of five replicates
for each dough was used in the statistical calculations. Samples (50 x 5 0 m m ) were cut from the middle of the Danish pastries. All tests were carried out at 23 °C. The loading cell was set at 5 N, the compression speed was 250mm/min, and the blades were adjusted to go 4 0 m m through the samples and out on the other side.
Colour analysis The colour of the crust of the Danish pastries was measured using a Minolta CR 200 Chroma Meter ( 8 m m head) (Minolta Camera Co. Ltd., Osaka, Japan) and expressed by CIE (1976) L* (whiteness), a* (redness) and b* (yellowness) values (6). Illuminant D65 was used for analysis. Five Danish pastries produced from each of the 33 doughs were measured at three different places on the crust (average of 15 used for each dough). The average standard deviations for L*, a* and b* were 2.6, 1.5, 1.4, respectively.
Statistical analysis Principal component analysis is a statistical technique which treats all variables simultaneously (7). The data are modelled in terms of a few significant factors, plus errors or residuals. The factors contain the main phenomena or systematic variability present in the data, the residuals represent the variability interpreted as noise. Prior to PCA, the parameters were scaled to have zero mean. For the sensory variables and the Instron textural measurements only mean subtraction was used. Explained variance for each PCA factor was also determined by leverage correction (8), a method which is an approximation to cross-validation (9). The sensory data were further subjected to analysis of variance (see e.g. Scheffe (10)) with each variable treated separately. A cross-classification model with only main effects for shortening type and concentration was applied. The colour measurements were analysed by an A N O V A main effect model.
Results and Discussion The mean and standard deviation for all attributes used for describing the Danish pastries were calculated and are reported in Table 2. As shown, the deviation is quite different for the different attributes, ranging from 0.2 for colour hue to 2.4 for butter odour and taste.
ANOVA fo~ sensory attributes A N O V A was performed using a model with only main effects for shortening type and shortening concentration. The results are reported as F-values in Table 3. Interaction between shortening type and shortening concentration cannot be a part of the model since there are no replicates in this experiment. This means that the significances should not be interpreted too rigidly. The ranking of the F-values is more important. As shown in Table 3, there are differences between the attributes. In addition, the attributes with the lowest standard deviations in Table 2 have the lowest F-values for both shortening type and shortening concentration. This indicates that the attributes with lowest standard deviation, namely
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Table 2
Mean (.~) and standard deviation (s x) of sensory attributes of Danish pastries Sensory attributes
.~*
Crust glossiness Whiteness Colour hue Co]our strength Sponginess Butter odour Oil odour Butter taste Oil taste Saltiness Rancidity Crispness Juiciness Firmness After-taste Mouth coating
2.6 5.4 2.5 4.3 4.7 4.4 3.4 4.4 3.4 3.3 1.4 5.7 5.4 3.4 3.9 3.3
sx ..... 0.5 1.0 0.2 1.7 1.7 2.4 1.6 2.4 1.6 0.5 0.3 1.0 0.6 0.5 0.4 0.9
* Scale 1 to 9. Table 3 F-values for the effects of type and concentration of shortening on sensory attributes of Danish pastries F-values for shortening Sensory attributes
Type
Concentration
Crust glossiness Whiteness Colour hue Colour strength Sponginess Butter odour Oil odour Butter taste Oil taste Saltiness Rancidity Crispness Juiciness Firmness After-taste Mouth coating
3.0 25.3 1.2 50. I 1.5 45.1 17.7 39.9 16.9 9.5 3.7 5.9 2.7 2.3 5.9 12.9
0.5 40.1 2.0 22.2 31.9 1.8 0.6 2.2 0.1 1.7 I. I 33.2 I1.5 10.7 1.8 1.4
The I% percentile for shortening type was 3.4, for shortening concentration 5.8.
crust glossiness, saltiness, rancidity, after-taste and colour hue contain mainly noise and cannot be used to distinguish between samples. Shortening type was significant for the attributes whiteness, colour strength, butter and oil odour and taste, and mouth coating; shortening concentration for the attributes whiteness. colour strength, sponginess and crispness. Thus, taste and odour were influenced by shortening type. texture by shortening concentration and colour by both type and concentration of shortening.
no influence on the results at all. The latter is consistent with the results (Table 3) above which indicated that these variables cannot be used to distinguish between the samp¿es. The first two principal components accounted for 63% and 17%, i.e. about 80% of the total variance. The presence of these two main factors was confirmed by leverage correction. A third principal component accounting for less than 10% of the variance was not included in the interpretations. The Ioadings and scores for the first two principal components are presented in Figs 1 and 2. In the scoreplot, all Danish pastries made with shortenings containing milk fat, i.e. no. 1, 2, 3, 4, 6 and 7 (Table 1) are oriented to the right, and all Danish pastries made with shortenings containing vegetable oil i.e. no. 5, 8, 9, 10 and 11 (Table 1) are oriented to the left of the average. This indicates that this component is mainly related to shortening type. On the other hand the second component is mainly related to shortening concentration, i.e. Danish pastries made with lower concentrations appear above the average, while Danish pastries made with higher concentrations are below the average. There is, however, also a certain relationship with which shortening type is used e.g. pastries with Croissant, French milk fat fraction (shortening no. 6) are lower down in the plot than pastries with pure anhydrous Norwegian milk fat (shortening no. 1) or 800g/kg Norwegian milk fat fraction (shortening no. 2). There is also a certain tendency to move from left to right in the plot when the shortening concentration increases. Loading plots are used to visualize the contributions of the various sensory attributes to the components. It is clear that component 1 is most strongly related to butter taste and odour with positive loadings and oil taste and odour with negative ]oadings. Colour strength and whiteness also play a small part of the interpretation of this component. Component 2 is mainly related to sponginess and whiteness above the average and colour strength and crispness below the average. From this we can conclude that Danish pastries made with shortenings no. 1, 2, 3, 4, 6 and 7 have more butter taste, butter odour and colour strength than the rest which have more by oil taste, oil odour and whiteness. When the concentration of all shortening types increases, the sponginess and whiteness decreases, while colour strength and crispness increases. Danish pastries with 350g/kg Croissant, French milk fat (no. 6) or MD-Foods, Danish milk fat (no. 7) are more crispy and flaky than pastries made of all four Norwegian milk fat shortenings (No. 1-4). Danish pastries made of all the margarine type shortenings at 350 g/kg level were spongy. All interpretations of PCA plots concerning the effect of the two components were in good agreement with the A N O V A results obtained above.
PCA for sensory attributes PCA was performed on the raw data, after mean subtraction, but without any standardizing to equal variance. This means that the variables with the largest standard deviation, for instance butter odour and taste, have the largest effect on the analysis, and the variables with the smallest standard deviation, for instance colour hue and rancidity, have practically
PCA for instrumental textural analysis The lnstron textural measurements were handled by the same PCA technique as used for the sensory data. Almost 95% of the variation was explained by the two first components. The loadings for the two components are presented in Fig. 3
74
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1st Principal component Fig. 2 Score plot for the two first factors obtained by PCA for sensory attributes of Danish pastries formulated with 11 different shortenings. For identification of sample numbers, see Table 1. The second number in the code corresponds to shortening concentration: 1 = 350 g/kg, 2 = 500 g/kg, 3 = 600 g/kg as a function of compression. Component 1 has approximately the same shape as the Instron curves themselves, and is related to whether the peak is high or low. This first component axis is therefore interpreted as a firmness axis. The second component axis is related to whether the peak is to the right or left of the average. This second component is therefore interpreted as related to elasticity. The score plot (Fig. 4) shows that samples with higher shortening concentrations were positioned to the left of the plot, samples with lower concentrations to the right. Bearing the interpretation above in mind, this means that as the shortening concentration increases, the firmness will
decrease. In addition, all samples prepared with MD-Foods, Danish milk fat fraction (no. 7) or pure anhydrous Norwegian milk fat (no. 1), were to the right of the average, indicating these samples to be firmer than the average. Furthermore, samples with 800g/kg Norwegian milk fat fraction (no. 4) are positioned to the left and are therefore less firm than the average. There was also an indication that samples with 800 g/kg Norwegian milk fat fraction (no. 2) were more elastic than the average, while samples containing Veba Rullemargarin (no. 8) and Veba Puffmargarin (no. 9) were less elastic than the average. Component 2 distinguishes the different shortening types, but the ingredients in
75
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Loadings for Instron texture curves for the factor 1 ( different shortenings Fig. 3
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1st Principal component P C A score plots of Instron texture curves for factor 1 vs, factor 2. For identification of sample numbers, see Table 1. The second number in the code corresponds to shortening concentration: 1 = 3 5 0 g / k g , 2 = 5 0 0 g / k g , 3 = 6 0 0 g / k g
Fig. 4
the shortenings that caused this difference were difficult to identify. The results from the textural measurements indicating that samples with higher shortening concentration were softer, were in good agreement with the results from the sensory analysis.
ANOVA for colour parameters The average and standard deviation for the colour parameter L* (whiteness), a* (redness) and b* (yellowness) were calculated (Table 4). A N O V A was performed on these averages using only the
main effects for shortening type and shortening concentration (Table 5). Significance was only apparent for the influence of shortening concentration on a* (redness). As for the sensory data, since interactions are not present in the model, the significances should not be interpreted too rigidly, only as an indication. We also tried PCA on the colour data, but the results were very difficult to interpret. The reason for so little structure in these data was the fact that the variation within samples was equal to or larger than the variation between samples (Table 4). In other words, the instrumental colour measurements of Danish pastries varied
76
Iwt/vol.28 (1995) No. 1
Table 4
Mean (.~) and standard deviation (s x) of colour parameters. L* (whiteness), a* (redness) and b* (yellowness) of Danish pastries. For identification of sample numbers, see Table 1 L*
a*
b*
Shortening and sample no.
.~-
sx
.~
sx
.i-
sx
I.I 1.2 1.3 2.1 2.2 2.3 3.1 3.2 3.3 4.1 4.2 4.3 5. I 5.2 5.3 6.1 6.2 6.3 7. I 7.2 7.3 8.1 8.2 8.3 9.1 9.2 9.3 10.1 10.2 10.3 I 1.1
52.1 49.2 5O.6 48.3 53.2 52.4 47.8 50.9 49.5 54.2 50.1 54.7 56.1 54.6 52.4 44.1 51.5 50.1 49.8 53.4 51.1 53.7 52.0 50.4 51.5 52.1 50.7 55.0 54.2 49.9 54.6
11.2
51.5
I 1.3 All 33 productions
48.3 51.5
2.9 4.3 3.3 2.7 3.3 2.6 4.2 1.8 7.1 4.3 2.9 2.5 2.4 2.4 3.5 3.2 2.1 3.0 4.5 2.9 4.2 4.4 3.6 3.0 1.8 2.8 3.5 3.1 2.8 3.3 3.3 2.0 2.8 2.6
8.6 7.6 7.1 10.1 7.3 7.0 9.7 8.4 7.7 7.5 7.3 5.1 7.8 6.1 6.8 12.2 6.9 6.7 9.8 8.0 8.4 8.4 7.0 7.3 10.1 6.0 7. I 8.5 5.3 5.8 7.3 8.0 7.5 7.7
1.5 1.3 1.6 1.6 1.6 1.6 2.8 0.6 .4 .3 .9 .1 .2 .4 .4 2.1 0.9 2.0 3.3 1.3 2.4 2.0 1.2 2.0 1.3 1.1 1.4 2.1 1.7 1.4 1.4 1.1 1.0 1.5
27.9 27.3 26.3 28.5 26.9 27.3 26.2 28.5 27.0 28.9 26.6 27.5 29.4 26.7 27.7 25.7 26.3 27.7 26.7 27.9 30.8 28.1 25.7 27.3 29.8 26.1 26.4 27.4 25.6 24.3 27.3 27.1 25.1 27.2
2.1 2. I 2.8 1.3 1.5 2.9 1.9 1.3 1.8 2.2 3.4 3.1 2.2 2.8 3.3 3.6 1.5 2.0 3.9 2.8 3.0 2.3 2.2 2.4 1.9 2.6 2.4 2.0 1.3 2.8 3.1 2.4 1.9 1.4
Table 5
F-values for the effect of shortening type and concentration on colour measurements of Danish pastries. The percentiles are the same as for Table 3 F-values for shortening Colour measurements
Type
Concentration
L* a* b*
1.47 1.81 0.95
0.6 I 15.97 1.80
more within one batch than between the Danish pastries made with different shortening types. Since sensory colour m e a s u r e m e n t s were quite good at discriminating b e t w e e n the different samples, this indicates that the large within sample variation o b s e r v e d for the instrumental data was averaged out by the sensory panel. In conclusion, the roll-in shortenings used in Danish pastries in this e x p e r i m e n t distinguish between shortening type and concentrations shown both by sensory analyses and instrumental texture analyses. The roll-in shortening type influenced the taste, odour and colour, and roll-in shortening concentration influenced the texture and colour.
Acknowledgements Technical assistance from A l f Nielsen is greatly appreciated. W e w o u l d also like to thank the N o r w e g i a n Dairy Association for financial support.
References 1 SULTAN, W. J. Practical Baking. Westport, CN: The Avi Publishing Company, Inc. (1965) 2 MATZ. S. A. Formulas and Processes for Bakers. Essex: Elsevier Science Publishers Ltd. (1989) 3 TOLBOE, O. Physical characteristics of butter fat and their influence on the quality of Danish pastry and cookies. Pro-
ceedings of the Scandinavian Forum for Lipid Research and Technology. Fats (lipids) in Baking and Extrusion. Gcteborg, Sweden, April 1983, p. 97 (1984) 4 BAARDSETH, P., N/ES, T., MIELNIK, J., SKREDE, G., HOELAND, S. AND EtDE, O. Dairy ingredient effects on sausage sensory properties studied by principal component analysis. Journal of Food Science, 5% 822 (1992) 5 BLAKENEY, A. B. Instron measurement of cooked-rice texture.
Proceedings of the Workshop on Chemical Aspects of Rice Grain Quali~. International Rice Grain Institute Oct 1978, 1979 edn. p. 343 (1979) 6 HUNTER, R. S. AND HAROLD, R. W. The Measurement of Appearance. New York: John Wiley & Sons (1987) 7 MARDtA, K. V., KEt~T, J. T. AND BtBBY, J. M. Multivariate Analysis. London: Academic Press (1980) 8 MARTENS, H. AND N~s, T. Multivariate Calibration. Chichester, UK: John Wiley and Sons (1989) 9 STONE, M. Cross-validatory choice and assessment of statistical prediction. Journal of the Royal Statistic" Society, B, 36, 111 (1974) 10 SCHEFFE, H. The Analysis of Variance. London: John Wiley and Sons (1959)
77
Roll-in Shortenings Effects on Danish Pastries Sensory Properties Studied by Principal Component Analysis Pernille Baardseth, Tormod Naes and Gjermund Vogt Norwegian Food Research Institute, MATFORSK, Osloveien 1, N-1430/ks (Norway) (Received March 29.1994: accepted August 17. 1994)
The effects of I1 different shortenings, either made of milk fat or vegetable oil. at three concentrations (350. 500 and 600 g/kg) opt sensoo' properties, and instrumental texture and colour of Danish pastries were investigated. Principal component analysis (PCA) revealed m,o dominating components for sensory properties; the first to shortening type and the second to shortening concentration. Results were verified by analysis of variance (ANO VA). Texture and colour were measured to verif3, the senso O, results and analysed by the same statistical methods using PCA and ANOVA. re.spectively.
Introduction Danish pastry is made from a rich yeast dough which has been layered with shortening by repeated folding and rolling steps in a process somewhat similar to that used for making puff pastry. The result is a silky tender crumb of characteristic appearance and a glossy flaky crust. The flakiness depends on the formation of thin films of gluten protein which trap water vapour and carbon dioxide from fermentation. Thus gluten films must be separated by continuous layers of fat in order not to form a three-dimensional structure. The sheets of fat act as a barrier preventing adjacent dough layers from fusing together while they are being reduced in thickness during the folding and rolling process. The main demands of Danish pastry roll-in shortening are therefore good spreadability and a plastic range extending to 10°C so that it does not become brittle when cooled and rupture the layering. Butter, margarine or specially fabricated vegetable oil shortenings can be used for the roll-in material (1, 2). Milk fat has to be fractionated to achieve these rheological properties (3). Sensory quality of a food commodity consists of several characteristics. Principal component analysis (PCA) is a useful technique for studying interdependencies and underlying dimensions of such characteristics. Baardseth et al. (4) used this technique to study the effects of dairy ingredients on the sensory properties of sausages. PCA revealed three dominating factors for sensory analysis. The results were verified by analysis of variance (ANOVA). The results of the sensory analysis were further verified by instrumental texture and colour analysis using PCA and ANOVA, respectively. These techniques prove to be useful in product development. The purpose of the present study was to demonstrate the usefulness of PCA to assess the influence of 11 roll-in shortenings made of milk fat or vegetable oil on important sensory characteristics of Danish pastries. For comparison, the data were also analysed by ANOVA. The 11 shortenings
were each used at three concentrations and the final products evaluated by descriptive sensory analysis. To verify the sensory results, colour and texture were determined instrumentally, the results being analysed by the same statistical methods.
Materials and Methods Dough preparation and processing
Wheat flour (570g/kg), water (213g/kg), fresh eggs ( 106 g/kg), sugar (43 g/kg), yeast (43 g/kg), skim-milk powder (21 g/kg) and salt (4g/kg) were used to make a dough batch. Eleven shortenings (Table 1), tempered at 18 °C for 7 d, were folded into the flat dough at three concentrations (350, 500 or 600 g/kg) to make a total of 33 doughs. The dough was kneaded with a Diosna kneading arm mixer (SP 40 D.U. S6hne, Osnabriick, Germany) for l l0s at 90rpm. The temperature of the water (2 °C), liquid mixture (6 °C), flour ( - 15 °C) and dough (6 °C) were recorded. The rolling and folding process occurred in four stages using a roller (Rollfix, A. Fritsch K.G. Markt Einersheim, Germany). The stages comprised sequential rollings to defined thicknesses, folding and one or more rollings followed by a rest period at 5 °C under plastic for 30 min (between stage I and 2 and stage 2 and 3) or 60min (between stage 3 and 4). Stage 1: roll to (mm) 30, 25, 20, 17.5, 15, 12.5; fold; roll to 30mm; rest 30min. Stage 2: roll to (mm) 25, 20, 17.5, 15, 12.5; fold; roll to 30 mm; rest 30 min. Stage 3: roll to (mm) 25, 20, 17.5, 15, 12.5, 10; fold; roll to (mm) 25, 20, 17.5, 15; rest 60 min. Stage 4: roll to (mm) 12.5, 10, 8.5, 7, 6, 5, 4, 3.5. The dough was cut into I0 x 10cm pieces, and stored uncovered at 5 °C until the next day. The dough pieces were proofed at 35 °C and 65% relative humidity for 65 min and baked in an oven (Bago-Line, Bex 1.0, Vester Aby, Denmark) at 220°C for 10.5min. The Danish pastries were cooled at room temperature (about 22°C) for l h before analysis. The productions were randomized.
0023-6438/95/010072 + 06 $08.00/0 (~) 1995 Academic Press Limited
72
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Table 1 Identification number and description of shortenings used in Danish pastries Shortening no.
10 I1
Shortening type Pure anhydrous Norwegian milk fat, plasticized, melting point 38 °C 800g/kg Norwegian milk fat fraction, plasticized, skim-milk powder, salt and lactic acid were added to the water phase, melting point 38 °C 980g/kg Norwegian milk fat fraction, plasticized, emulsifier and soya lecithin were added, melting point 38 °C 800g/kg Norwegian milk fat fraction, plasticized, skim milk powder, salt and lactic acid were added to the water phase, emulsifier and soya lecithin were added to the fat phase, melting point 38 °C Idun Rullemargarin. Luxuswiener; a commercial Norwegian roll-in shortening consisting of partially hydrogenated vegetable oil, water, salt, emulsifier and citric acid, melting point 37 °C Croissant, French milk fat fraction, plasticized, melting point 40°C MD-Foods, Danish milk fat fraction, plasticized, melting point 42 °C Veba Rullemargarin, a commercial Norwegian rollin shortening consisting of hydrogenated vegetable oil, vegetable oil, hydrogenated fish oil, water, skimmilk powder, salt, lecithin and emulsifier, melting point 39 °C Veba Puffmargarin. a commercial Norwegian roll-in shortening consisting of hydrogenated fish oil, vegetable oil, water, skim-milk powder, salt, lecithin and emulsifier, melting point 41 °C BBB-Wienervare, a commercial Norwegian roll-in shortening consisting of vegetable oil, water, salt, emulsifier and sodium citrate, melting point 39 °C Pals Wienervare, a commercial Norwegian roll-in shortening consisting of hydrogenated fish oil, vegetable oil, water, salt, emulsifier and lactic acid, melting point 39 °C
Sensory evaluation The sensory analysis was performed according to a descriptive sensory strategy. The sensory panel consisted of 10 trained panellists, and a continuous non-structured scale was used for evaluation. The left side of the scale, corresponding to the lowest intensity of each attribute, was given a value of 1.0 and the right side, corresponding to the highest intensity, was given a value of 9.0 (Senstec, Tecator, Htigan~is, Sweden). The properties evaluated were crust glossiness, whiteness, colour hue, colour strength, sponginess (vs. flakiness), butter odour, oil odour, butter taste, oil taste, saltiness, rancidity, crispness, juiciness, firmness, after-taste, mouth coating from fat. The paneilists were trained for the sensory characteristics of the product before the main trial, but they were not informed about the purpose of the experiment. Each panellist was given one Danish pastry at a time in random order and told to cut it into two with a knife to judge the flake structure and colour. No replicates were performed.
Instrumental textural analysis Firmness of the Danish pastries was determined by compression using a Kramer shear cell according to Blakeney (5), on an Instron Testing Instrument, model 4202 (Instron Ltd, High Wycombe, U.K.). The average of five replicates
for each dough was used in the statistical calculations. Samples (50 x 5 0 m m ) were cut from the middle of the Danish pastries. All tests were carried out at 23 °C. The loading cell was set at 5 N, the compression speed was 250mm/min, and the blades were adjusted to go 4 0 m m through the samples and out on the other side.
Colour analysis The colour of the crust of the Danish pastries was measured using a Minolta CR 200 Chroma Meter ( 8 m m head) (Minolta Camera Co. Ltd., Osaka, Japan) and expressed by CIE (1976) L* (whiteness), a* (redness) and b* (yellowness) values (6). Illuminant D65 was used for analysis. Five Danish pastries produced from each of the 33 doughs were measured at three different places on the crust (average of 15 used for each dough). The average standard deviations for L*, a* and b* were 2.6, 1.5, 1.4, respectively.
Statistical analysis Principal component analysis is a statistical technique which treats all variables simultaneously (7). The data are modelled in terms of a few significant factors, plus errors or residuals. The factors contain the main phenomena or systematic variability present in the data, the residuals represent the variability interpreted as noise. Prior to PCA, the parameters were scaled to have zero mean. For the sensory variables and the Instron textural measurements only mean subtraction was used. Explained variance for each PCA factor was also determined by leverage correction (8), a method which is an approximation to cross-validation (9). The sensory data were further subjected to analysis of variance (see e.g. Scheffe (10)) with each variable treated separately. A cross-classification model with only main effects for shortening type and concentration was applied. The colour measurements were analysed by an A N O V A main effect model.
Results and Discussion The mean and standard deviation for all attributes used for describing the Danish pastries were calculated and are reported in Table 2. As shown, the deviation is quite different for the different attributes, ranging from 0.2 for colour hue to 2.4 for butter odour and taste.
ANOVA fo~ sensory attributes A N O V A was performed using a model with only main effects for shortening type and shortening concentration. The results are reported as F-values in Table 3. Interaction between shortening type and shortening concentration cannot be a part of the model since there are no replicates in this experiment. This means that the significances should not be interpreted too rigidly. The ranking of the F-values is more important. As shown in Table 3, there are differences between the attributes. In addition, the attributes with the lowest standard deviations in Table 2 have the lowest F-values for both shortening type and shortening concentration. This indicates that the attributes with lowest standard deviation, namely
73
lwt/vol. 28 (1995) No. 1
Table 2
Mean (.~) and standard deviation (s x) of sensory attributes of Danish pastries Sensory attributes
.~*
Crust glossiness Whiteness Colour hue Co]our strength Sponginess Butter odour Oil odour Butter taste Oil taste Saltiness Rancidity Crispness Juiciness Firmness After-taste Mouth coating
2.6 5.4 2.5 4.3 4.7 4.4 3.4 4.4 3.4 3.3 1.4 5.7 5.4 3.4 3.9 3.3
sx ..... 0.5 1.0 0.2 1.7 1.7 2.4 1.6 2.4 1.6 0.5 0.3 1.0 0.6 0.5 0.4 0.9
* Scale 1 to 9. Table 3 F-values for the effects of type and concentration of shortening on sensory attributes of Danish pastries F-values for shortening Sensory attributes
Type
Concentration
Crust glossiness Whiteness Colour hue Colour strength Sponginess Butter odour Oil odour Butter taste Oil taste Saltiness Rancidity Crispness Juiciness Firmness After-taste Mouth coating
3.0 25.3 1.2 50. I 1.5 45.1 17.7 39.9 16.9 9.5 3.7 5.9 2.7 2.3 5.9 12.9
0.5 40.1 2.0 22.2 31.9 1.8 0.6 2.2 0.1 1.7 I. I 33.2 I1.5 10.7 1.8 1.4
The I% percentile for shortening type was 3.4, for shortening concentration 5.8.
crust glossiness, saltiness, rancidity, after-taste and colour hue contain mainly noise and cannot be used to distinguish between samples. Shortening type was significant for the attributes whiteness, colour strength, butter and oil odour and taste, and mouth coating; shortening concentration for the attributes whiteness. colour strength, sponginess and crispness. Thus, taste and odour were influenced by shortening type. texture by shortening concentration and colour by both type and concentration of shortening.
no influence on the results at all. The latter is consistent with the results (Table 3) above which indicated that these variables cannot be used to distinguish between the samp¿es. The first two principal components accounted for 63% and 17%, i.e. about 80% of the total variance. The presence of these two main factors was confirmed by leverage correction. A third principal component accounting for less than 10% of the variance was not included in the interpretations. The Ioadings and scores for the first two principal components are presented in Figs 1 and 2. In the scoreplot, all Danish pastries made with shortenings containing milk fat, i.e. no. 1, 2, 3, 4, 6 and 7 (Table 1) are oriented to the right, and all Danish pastries made with shortenings containing vegetable oil i.e. no. 5, 8, 9, 10 and 11 (Table 1) are oriented to the left of the average. This indicates that this component is mainly related to shortening type. On the other hand the second component is mainly related to shortening concentration, i.e. Danish pastries made with lower concentrations appear above the average, while Danish pastries made with higher concentrations are below the average. There is, however, also a certain relationship with which shortening type is used e.g. pastries with Croissant, French milk fat fraction (shortening no. 6) are lower down in the plot than pastries with pure anhydrous Norwegian milk fat (shortening no. 1) or 800g/kg Norwegian milk fat fraction (shortening no. 2). There is also a certain tendency to move from left to right in the plot when the shortening concentration increases. Loading plots are used to visualize the contributions of the various sensory attributes to the components. It is clear that component 1 is most strongly related to butter taste and odour with positive loadings and oil taste and odour with negative ]oadings. Colour strength and whiteness also play a small part of the interpretation of this component. Component 2 is mainly related to sponginess and whiteness above the average and colour strength and crispness below the average. From this we can conclude that Danish pastries made with shortenings no. 1, 2, 3, 4, 6 and 7 have more butter taste, butter odour and colour strength than the rest which have more by oil taste, oil odour and whiteness. When the concentration of all shortening types increases, the sponginess and whiteness decreases, while colour strength and crispness increases. Danish pastries with 350g/kg Croissant, French milk fat (no. 6) or MD-Foods, Danish milk fat (no. 7) are more crispy and flaky than pastries made of all four Norwegian milk fat shortenings (No. 1-4). Danish pastries made of all the margarine type shortenings at 350 g/kg level were spongy. All interpretations of PCA plots concerning the effect of the two components were in good agreement with the A N O V A results obtained above.
PCA for sensory attributes PCA was performed on the raw data, after mean subtraction, but without any standardizing to equal variance. This means that the variables with the largest standard deviation, for instance butter odour and taste, have the largest effect on the analysis, and the variables with the smallest standard deviation, for instance colour hue and rancidity, have practically
PCA for instrumental textural analysis The lnstron textural measurements were handled by the same PCA technique as used for the sensory data. Almost 95% of the variation was explained by the two first components. The loadings for the two components are presented in Fig. 3
74
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1st Principal component Fig. 2 Score plot for the two first factors obtained by PCA for sensory attributes of Danish pastries formulated with 11 different shortenings. For identification of sample numbers, see Table 1. The second number in the code corresponds to shortening concentration: 1 = 350 g/kg, 2 = 500 g/kg, 3 = 600 g/kg as a function of compression. Component 1 has approximately the same shape as the Instron curves themselves, and is related to whether the peak is high or low. This first component axis is therefore interpreted as a firmness axis. The second component axis is related to whether the peak is to the right or left of the average. This second component is therefore interpreted as related to elasticity. The score plot (Fig. 4) shows that samples with higher shortening concentrations were positioned to the left of the plot, samples with lower concentrations to the right. Bearing the interpretation above in mind, this means that as the shortening concentration increases, the firmness will
decrease. In addition, all samples prepared with MD-Foods, Danish milk fat fraction (no. 7) or pure anhydrous Norwegian milk fat (no. 1), were to the right of the average, indicating these samples to be firmer than the average. Furthermore, samples with 800g/kg Norwegian milk fat fraction (no. 4) are positioned to the left and are therefore less firm than the average. There was also an indication that samples with 800 g/kg Norwegian milk fat fraction (no. 2) were more elastic than the average, while samples containing Veba Rullemargarin (no. 8) and Veba Puffmargarin (no. 9) were less elastic than the average. Component 2 distinguishes the different shortening types, but the ingredients in
75
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Loadings for Instron texture curves for the factor 1 ( different shortenings Fig. 3
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Fig. 4
the shortenings that caused this difference were difficult to identify. The results from the textural measurements indicating that samples with higher shortening concentration were softer, were in good agreement with the results from the sensory analysis.
ANOVA for colour parameters The average and standard deviation for the colour parameter L* (whiteness), a* (redness) and b* (yellowness) were calculated (Table 4). A N O V A was performed on these averages using only the
main effects for shortening type and shortening concentration (Table 5). Significance was only apparent for the influence of shortening concentration on a* (redness). As for the sensory data, since interactions are not present in the model, the significances should not be interpreted too rigidly, only as an indication. We also tried PCA on the colour data, but the results were very difficult to interpret. The reason for so little structure in these data was the fact that the variation within samples was equal to or larger than the variation between samples (Table 4). In other words, the instrumental colour measurements of Danish pastries varied
76
Iwt/vol.28 (1995) No. 1
Table 4
Mean (.~) and standard deviation (s x) of colour parameters. L* (whiteness), a* (redness) and b* (yellowness) of Danish pastries. For identification of sample numbers, see Table 1 L*
a*
b*
Shortening and sample no.
.~-
sx
.~
sx
.i-
sx
I.I 1.2 1.3 2.1 2.2 2.3 3.1 3.2 3.3 4.1 4.2 4.3 5. I 5.2 5.3 6.1 6.2 6.3 7. I 7.2 7.3 8.1 8.2 8.3 9.1 9.2 9.3 10.1 10.2 10.3 I 1.1
52.1 49.2 5O.6 48.3 53.2 52.4 47.8 50.9 49.5 54.2 50.1 54.7 56.1 54.6 52.4 44.1 51.5 50.1 49.8 53.4 51.1 53.7 52.0 50.4 51.5 52.1 50.7 55.0 54.2 49.9 54.6
11.2
51.5
I 1.3 All 33 productions
48.3 51.5
2.9 4.3 3.3 2.7 3.3 2.6 4.2 1.8 7.1 4.3 2.9 2.5 2.4 2.4 3.5 3.2 2.1 3.0 4.5 2.9 4.2 4.4 3.6 3.0 1.8 2.8 3.5 3.1 2.8 3.3 3.3 2.0 2.8 2.6
8.6 7.6 7.1 10.1 7.3 7.0 9.7 8.4 7.7 7.5 7.3 5.1 7.8 6.1 6.8 12.2 6.9 6.7 9.8 8.0 8.4 8.4 7.0 7.3 10.1 6.0 7. I 8.5 5.3 5.8 7.3 8.0 7.5 7.7
1.5 1.3 1.6 1.6 1.6 1.6 2.8 0.6 .4 .3 .9 .1 .2 .4 .4 2.1 0.9 2.0 3.3 1.3 2.4 2.0 1.2 2.0 1.3 1.1 1.4 2.1 1.7 1.4 1.4 1.1 1.0 1.5
27.9 27.3 26.3 28.5 26.9 27.3 26.2 28.5 27.0 28.9 26.6 27.5 29.4 26.7 27.7 25.7 26.3 27.7 26.7 27.9 30.8 28.1 25.7 27.3 29.8 26.1 26.4 27.4 25.6 24.3 27.3 27.1 25.1 27.2
2.1 2. I 2.8 1.3 1.5 2.9 1.9 1.3 1.8 2.2 3.4 3.1 2.2 2.8 3.3 3.6 1.5 2.0 3.9 2.8 3.0 2.3 2.2 2.4 1.9 2.6 2.4 2.0 1.3 2.8 3.1 2.4 1.9 1.4
Table 5
F-values for the effect of shortening type and concentration on colour measurements of Danish pastries. The percentiles are the same as for Table 3 F-values for shortening Colour measurements
Type
Concentration
L* a* b*
1.47 1.81 0.95
0.6 I 15.97 1.80
more within one batch than between the Danish pastries made with different shortening types. Since sensory colour m e a s u r e m e n t s were quite good at discriminating b e t w e e n the different samples, this indicates that the large within sample variation o b s e r v e d for the instrumental data was averaged out by the sensory panel. In conclusion, the roll-in shortenings used in Danish pastries in this e x p e r i m e n t distinguish between shortening type and concentrations shown both by sensory analyses and instrumental texture analyses. The roll-in shortening type influenced the taste, odour and colour, and roll-in shortening concentration influenced the texture and colour.
Acknowledgements Technical assistance from A l f Nielsen is greatly appreciated. W e w o u l d also like to thank the N o r w e g i a n Dairy Association for financial support.
References 1 SULTAN, W. J. Practical Baking. Westport, CN: The Avi Publishing Company, Inc. (1965) 2 MATZ. S. A. Formulas and Processes for Bakers. Essex: Elsevier Science Publishers Ltd. (1989) 3 TOLBOE, O. Physical characteristics of butter fat and their influence on the quality of Danish pastry and cookies. Pro-
ceedings of the Scandinavian Forum for Lipid Research and Technology. Fats (lipids) in Baking and Extrusion. Gcteborg, Sweden, April 1983, p. 97 (1984) 4 BAARDSETH, P., N/ES, T., MIELNIK, J., SKREDE, G., HOELAND, S. AND EtDE, O. Dairy ingredient effects on sausage sensory properties studied by principal component analysis. Journal of Food Science, 5% 822 (1992) 5 BLAKENEY, A. B. Instron measurement of cooked-rice texture.
Proceedings of the Workshop on Chemical Aspects of Rice Grain Quali~. International Rice Grain Institute Oct 1978, 1979 edn. p. 343 (1979) 6 HUNTER, R. S. AND HAROLD, R. W. The Measurement of Appearance. New York: John Wiley & Sons (1987) 7 MARDtA, K. V., KEt~T, J. T. AND BtBBY, J. M. Multivariate Analysis. London: Academic Press (1980) 8 MARTENS, H. AND N~s, T. Multivariate Calibration. Chichester, UK: John Wiley and Sons (1989) 9 STONE, M. Cross-validatory choice and assessment of statistical prediction. Journal of the Royal Statistic" Society, B, 36, 111 (1974) 10 SCHEFFE, H. The Analysis of Variance. London: John Wiley and Sons (1959)
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