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The effect of the type and quantity of sugar-beet fibers on bread characteristics
Journal of Food Engineering 78 (2007) 1047–1053 www.elsevier.com/locate/jfoodeng
The effect of the type and quantity of sugar-beet fibers on bread characteristics Nada Filipovic *, Mirjana Djuric, Julianna Gyura Faculty of Technology, Carbohydrate Food Technology, Bul. Cara Lazara 1, 2100 Novi Sad, Serbia and Montenegro Received 23 June 2005; accepted 19 December 2005 Available online 28 February 2006
Abstract The application of fibers from various sources in food production is increasing due to their beneficial effects on human health. The aim of this paper is to investigate the effects of non-modified and modified sugar-beet fibers on dough and bread yield, bread volume and bread crumb quality. Dry sugar-beet fibers were ground, sieved through a laboratory sieve and a fraction with particles less than 95 lm was used for further treatment. It was hydrated for 24 h and pressed for removing excess water. In such a way, hydrated but non-modified fibers were obtained. Part of the non-modified fibers was exposed to a further treatment with H2O2, at the pH values: 3.5, 7 and 11 for the additional 24 h. Treated blends were neutralised, washed with tap and distilled water, pressed and blended to a homogenous mass with fine particles. In such a way modified fibers were obtained. Dough and bread were made from white flour, powdered vital gluten, salt and yeast (as it is used in regular bread production), without fibers, with non-modified fibers and with modified fibers. Experiments were planned so that the quantity of the applied fibers in the blends varied from 0% to 15%, while gluten quantity varied from 0% to 5%. Controlling characteristics of the product were: yield of dough and bread, volume, crumb quality. By applying the regression analysis method on the measured data, mathematical models for both fibers application were defined. Based on the experimental results as well as on the mathematical considerations following conclusions were drawn: increase of content of both fibers (non-modified and modified) increases yield of dough and bread but decreases volume of bread and bread crumb quality. On the other hand, increase of gluten quantity increases the volume of bread at small amounts of fibers; when fibers quantity increases, gluten proved ineffective. By the comparison of non-modified and modified fibers, the advantage is given to the non-modified fibers. An enrichment of bread with less than 10% of non-modified fibers, accompanied with a few percents of gluten, is highly recommended. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Bread; Sugar-beet fibers; Mathematical modelling
1. Introduction Products enriched with fibers from various sources can be considered as functional food, satisfying claims cited by Berghofer (2000), particularly when made of natural substances and when consumed every day. Such products contribute to specific metabolic pathways in an organism
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Corresponding author. Tel.: +381 21 6350 122; fax: +381 21 450 413. E-mail address: nfi[email protected] (N. Filipovic).
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(Seibel, 1998), causing positive effects to human health. Consumption of food rich in fibers can weaken or even prevent some diseases. Many years ago, a decrease of risk of colon cancer with an increase of intake of fibers-rich food was noticed (Whitehead, 1986). Also, diabetes incidences and hart-related problems can be reduced (Wang, Rosell, & Benedito de Barber, 2002). This must be related to the beneficial effects of fibers on the reduction of cholesterol level (Anderson, 1991). It is very well known that fibers possess dietary character. Not enzymatically degraded within the human digestive tract, fibers can have dietary role and can help in solving some digestive problems
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(Guillon, Auffret, Robertson, Thibault, & Barry, 1998; Wang et al., 2002). Food with high content of fibers causes hunger alleviating effect and, at the same time, does not cause binding minerals like calcium, magnesium and zinc (Stauffer, 1993; Westenhoefer, 2001). The recommendations for dietary fibers intake range from 25 to 30 g day1 (Asp, 2004, Chapter 1; USDA, 2002). On the other hand, bakery products, particularly bread, take a significant share in the food guide pyramid for daily food choices recommended by US Department of Health and Human Services. Therefore, the development of enriched bread with higher fibers content is one of the efficient ways to increasing the fibers intake (Goesaert et al., 2005; Sangnark & Noomhorm, 2004; Wang et al., 2002). The main source of fibrous materials, which can be incorporated into bakery products, is cereal bran, particularly wheat bran (Lai, Hoseney, & Davis, 1989; Ranhotra, Gelroth, Astroth, & Posner, 1990; Sidhu, Al-Hooti, & Al-Saqer, 1999) but also rice bran (AbdulHamid & Siew Luan, 2000). However, bran has a low water retention capacity and is adversely affecting crumb colour. So, investigations need to be directed toward other possible sources, including sugar-beet. In sugar-beet technology, pulp is remaining after sugar extraction as a waste product. Favourable sensory, physical and chemical characteristics, as well as microbiology, qualify this material as a valuable source of dietary fibers (Basman & Ko¨ksel, 1999; Persson, 1986). In comparison with cereal bran, sugar-beet fibers are characterized: (i) by low phytate, which is of particular concern to nutritionists because of its possible adverse effects on mineral absorption (Graf, 1986) and (ii) by better water binding and retention capacity, which is of particular interest for the baking industry (Stauffer, 1993). A wide range of research activities is related with the adjustment of fibers characteristics, by grinding (Auffret, Ralet, Guillon, Barry, & Thibault, 1994), by chemical treatment (Jasberg, Gould, Warner, & Navickis, 1989; Renard, Cre´peau, & Thibault, 1994) and by other methods. Very often, adjustments are undertaken in order to meet consumers’ preferences for white or light coloured bread. The aim of this investigation is to recommend optimal quality and quantity of sugar-beet fibers, which will guarantee satisfactory yield of dough, yield of bread, bread volume and crumb quality.
2.2. Methods Chemical composition (dry matter, proteins, mineral matters) of fibers was determined according methods specified by Reinefeld and Schneider (1983). 2.2.1. Water holding capacity of dietary fibers 2.5 g of dried ground fibers were suspended in 30 cm3 of distilled water at 30 °C in a centrifuge glass tube of 50 cm3 and thermostated for 30 min at 30 °C. Every 10 min the suspension was homogenized by stirring. The suspension was centrifuged at 5000g for 5 min and the swollen fibers particles were separated from the supernatant and weighed. The water holding capacity of the fibers was calculated from the difference between the hydrated (swollen) and dried sample (Stauffer, 1993). 2.2.2. Non-modified fibers The fibers after 60 min extraction of sugar-beet cossettes with sulphurous acid at 75 °C and pH = 5.7 are considered to be non-modified fibers. After drying at 80 °C fibers were ground in a Falling Number laboratory mill, type 3100, sieved through a laboratory sieve and a fraction with particles less than 95 lm were used for further treatment. Prior dough mixing, these types of fibers were hydrated for 24 h (ratio fibers to water = 1:4) at room temperature. 2.2.3. Modified fibers Prior to grinding non-modified fibers were hydrated for 24 h (ratio fibers to water = 1:9) at room temperature, then pressed in a laboratory press to remove excess water. After pressing they were treated with H2O2 up to blend concentration of 20 g L1 H2O2 and pH = 3.5. For treatments at neutral and alkaline media pH from 3.5 was adjusted to 7 and 11 with 10 M NaOH. After this 24 h chemical treatment, blends were neutralised with cc HCl until the pH reached the value 6–7 in all cases. Chlorine ions were washed with tap and distilled water to reach negative reaction to Cl ions. Modifies fibers were pressed to remove the excess water and blended to a homogenous mass with fine particles in a Braun blender.
2.1. Materials
2.2.4. Fibers determination Non-soluble fibers were determined according to AOAC Official Method 991.42 Insoluble Dietary Fibers in Foods and Food products Final Action 1994. Soluble fibers were determined according to AOAC Official Method 993.19 Soluble Dietary Fibers in Foods and Food products Final Action 1996.
Sugar-beet cossettes, safe product concerning heavy metals and microbiology (Gyura, Filipovic´, Sˇkrbic´, Sˇeresˇ, ˇ upic´, 2003), were used. &C White flour (ash and protein content 0.53 and 11.2% d.m. basis, respectively), powdered vital gluten (protein content 76% d.m. basis), salt and yeast were of commercial grade, as it is used in regular bread production.
2.2.5. Baking procedure Bread was baked according to the AACC method. Dough constituents were: flour (100–85%), sugar-beet fibers (0–15%), salt (2%), yeast (2.5%) and gluten powder (0–5%). Bread was baked approximately 15 min in a Chopin laboratory oven at 260 °C, until the mass of baked bread ranged between 135 and 137 g. The quality of bread
2. Materials and methods
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was characterised by dough yield, bread yield, bread volume and crumb quality. 3. Results and discussion 3.1. Results obtained by measurements The composition of fibers is presented in Table 1. The fibers modification by hydrogen peroxide contributes to significant increase in water holding capacity and favourable ratio of soluble to insoluble fibers. Treatment by hydrogen peroxide diminished fibers offcolour which is illustrated in Fig. 1. This decolourization effect enables fibers supplementation into white flour bread without adverse contribution to crumb and crust colour. Characteristics of bread made without fibers as well as with non-modified and modified fibers are given in Table 2. Each value represents mean of not less than 5 and not greater than 10 replicates and could be assumed reliable. It is obvious that the quantity of the applied fibers in the blends varied from 0% to 15%, while gluten quantity varied from 0% to 5%. Experiments proved that the quantity of fibers should not exceed 15%, due to extreme decrease of dough and bread characteristics with the increase of fibers content, while quantity of gluten should not exceed 5%, for the highest level of gluten causes poor mouth-feel of bread. A comparison between characteristics of non-fibers product and products with non-modified and modified fibers (in Table 2) shows that yields of dough and bread tend to increase with the increase of fibers quantity while, at the same time, volume of bread as well as crumb quality tend to decrease with the increase of fibers quantity. The
Table 1 Composition of non-modified and modified fibers Parameters
Non-modified fibers
Modified fibers
Dry matter content, % Water holding capacity, % Total fibers, % d.m. basis Insoluble fibers, % d.m. basis Soluble fibers, % d.m. basis Proteins, % d.m. basis Mineral matters, % d.m. basis
91.8 620 70.00 57.80 12.20 12.30 2.50
97.6 1596 94.33 61.12 33.21 4.16 9.42
Fig. 1. The colour of sugar-beet fibers: non-modified, modified, modified and fine mashed (from left to right).
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last conclusion might be explained by a weakening of gluten matrix, which is losing the ability to retain gases created during fermentation in the presence of fibers. Insufficient formation of gluten network influence dough handling that can be improved by adding gluten enhancing material like here applied vital gluten. However, gas retention is affected by the incorporated fibers quantity. As for the difference between effects of non-modified fibers and modified fibers on product characteristics, it seems that non-modified fibers should be given an advantage, if taking both volume of bread and crumb quality as the objectives and if analysing blends with gluten as improver. The comparison of the modified fibers, among themselves, from the same point of view, shows negligible difference between the fibers modified at pH = 3.5 and pH = 11, particularly in the case when the quantity of fibers does not exceed 10%. The fibers treated at pH = 7 proved acceptable when added at higher quantities, having in mind bread volume. However, their influence on crumb quality is improper. The relationship between fibers type’s, fibers quantity and gluten quantity, on one hand, and the product characteristics, on the other, became more evident after a graphical presentation of the results from Table 2. In the case of non-modified fibers application, 3-D diagrams of the important product characteristics (bread volume, and crumb quality) were presented in Fig. 2. An analysis shows that an increase of fibers content decreases volume of bread. On the other hand, the increase of gluten quantity increases volume of bread at small amounts of fibers; when fibers quantity increases, gluten proved ineffective. Similar conclusions can be drawn when crumb quality is analysed. In the case when modified fibers are applied, 3-D diagrams in Fig. 3 show that all three systems obey the same type of function and that the differences among fibers effects the bread volume almost negligibly. Quite contrary, when crumb quality is analysed (Fig. 4), great differences among fibers are found; the best are fibers treated at pH = 3.5, followed by fibers processed at pH = 11, while fibers obtained at pH = 7 decrease crumb quality by an unacceptable value. 3.2. Results obtained by mathematical modelling In order to obtain statistical approval of the conclusions above, the results from Table 2 were used in the regression analysis procedure and two mathematical models, for each particular characteristic, were derived: (i) the first one covers the case of enrichment with non-modified fibers and (ii) the second one deals with the case of modified fibers. In both cases a polynomial was chosen as a type of the regression, in accordance with the applied plan of experiments (Table 2). So, when non-modified fibers are applied a mathematical model, which proved the best, is given by Eq. (1): y ¼ b1 þ b2 x1 þ b3 x2 þ b4 x1 x2 þ b5 x21
ð1Þ
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Table 2 Measured values of dough and bread characteristics No
Fibers quantity, %
Gluten, %
Fibers modification, pH value
Dough yield, g
Bread yield, g
Bread volume, ml
Bread crumb quality, min = 0; max = 7
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
0 5 10 15 5 10 15 5 10 15 5 10 15 5 10 15 5 10 15 5 10 15 5 10 15
0 0 0 0 5 5 5 0 0 0 5 5 5 0 0 0 5 5 5 0 0 0 5 5 5
– – – – – – – 3.5 3.5 3.5 3.5 3.5 3.5 7 7 7 7 7 7 11 11 11 11 11 11
167.3 170.4 170.9 173.9 170.6 173.6 176.6 176.3 179.4 182.4 179.1 182.1 185.1 168.3 171.2 172.3 170.9 176.9 179.9 172.3 172.6 175.6 172.3 175.3 172.6
140.7 143.4 143.9 147.6 145.0 148.4 151.6 151.3 155.5 159.6 155.2 159.3 163.8 143.1 146.2 147.5 143.8 151.5 155.9 147.5 147.9 150.1 147.5 149.9 147.9
290 280 220 180 305 260 210 270 210 160 290 220 170 240 200 175 260 235 190 270 235 205 290 235 180
4.5 3.2 1.2 0.0 4.6 2.8 3.0 4.2 3.5 2.4 4.6 3.7 2.9 2.0 1.0 0.5 2.8 2.0 0.7 3.9 2.5 0.5 4.0 3.0 2.5
5
5 29 2
4
4. 5
22 2
30 6
Crumb quality Non-mod. fibers
4
23 6
2. 4
Gluten, %
Gluten, %
25 0 3
26 4 2
3
2. 9
2 3. 4
27 8
Volume, mL
1
20 8
4. 0
1
Non-mod. fibers
1. 9
19 4
0 .8 0 1. 3
0
0 0
2
4
6
8
10
12
14
16
0
2
4
6
Fibers, %
8
10
12
14
16
Fibers, %
Fig. 2. Bread volume and crumb quality as the functions of non-modified fibers and gluten quantity.
In the model (1), b’s are parameters, x1 signifies fibers quantity and x2 is gluten quantity while y denotes product characteristic. Parameter b1 corresponds to y in the case when x1 = x2 = 0, which means that b1 represents corresponding characteristic of dough and bread made from flour without other ingredients. The second and third terms represent the impact of single variable (fibers quantity and gluten quantity) on the product characteristics, the fourth term introduces a coupled effect of fibers and gluten while the last, the fifth term expresses quadratic effects of fibers quantity, giving highly non-linear character to the relationship (1).
Alternatively, the enrichment with modified fibers is modelled by Eq. (2): y ¼ b1 þ b2 x1 þ b3 x2 þ b4 x3 þ b5 x1 x2 þ b6 x1 x3 þ b7 x2 x3 þ b8 x21 þ b9 x23
ð2Þ
In the case when fibers are chemically treated, an additional variable (denoted as x3) should be introduced in the model. Through this variable, the influence of pH value of the chemical treatment on the product quality has been taken into account. Polynomial (2) contains also the parameter b1 the meaning of which is the same as in the
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5 304 4
208 28 8
Gluten, %
224 3
240 2 256
1 92
Volume, mL Modified fibers, pH=7
1 2 72 0 0
2
4
6
8
10
12
14
16
Fibers, %
5
5 192
4
30 4
208 4
208
306
222 236
G lut en, %
Gluten, %
224 3 240 256 2
Volume, mL
272
3 250 264 2 292
Volume, mL
Modified fibers, pH=3.5
1
194
278
1
Modified fibers,pH=11
17 6
288 0
0 0
2
4
6
8
10
12
14
16
Fibers, %
0
2
4
6
8
10
12
14
16
Fibers, %
Fig. 3. Bread volume as a function of modified fibers and gluten quantity.
previous case. The second, third and fourth terms, at the right hand side of the polynomial (2), represent the impact of single variable (fibers quantity, gluten quantity and pH value) on the product characteristics. The fifth, sixth and seventh terms are related to the interaction of: fibers and gluten, fibers and pH value as well as gluten and pH value, representing coupled impact of two variables on the product characteristics. Finally, the eight and ninth terms introduce quadratic effects of a single fibers and single pH value. Applying the regression analysis method to adequate series of data (Table 2), b-parameters were determined (for both mathematical models) and their t-factors were obtained in the same procedure. Each t-factor represents statistical measure of significance of each parameter in the mathematical models. They are presented in Tables 3 and 4 as fractions of 100% for every characteristic of the product. The significances are given twice; in the first part of each Table a difference between the significance of flour, on one hand, and significance of all the other components, on the other hand, is expressed, while in the second part the significances of other components are compared among themselves. In Table 3 significances for the system with non-modified fibers are shown. From the first part of Table 3, it can be concluded that both yields (dough and bread) depend at a level higher than 90% on flour characteristics. Bread volume is affected by flour quality at a level of 84%,
while the remaining 16% is associated with the influence of other ingredients (fibers and gluten). Crumb quality value depends at a level of 61.5% on the quality of flour while 38.5% of influences are related with the added components. Analysis of values from the second part of Table 3, leads to the conclusion that both yields (dough and bread) are linear functions of added components quantities. The yield of dough highly depends on fibers (74%) as well as on fibers interaction with gluten (25.5%); the yield of bread depends on fibers (63%), gluten (13.5%) and their interaction (23.5). The volume of bread and crumb quality are quadratic functions with double effect of fibers, linear and quadratic. Analysis of significances (from Table 2) shows that the fibers’ linear influence (20%) and quadratic influence (37%) on bread volume prevails compared to the influence of gluten (39%). In the case of crumb quality the linear effect of fibers (46%) dominates their interaction with gluten (43%). In Table 4 significances for the system with modified fibers are given. In this case, the yield of dough, the yield of bread and the volume of bread depend on flour characteristics at following levels: 84%, 75% and 68.5%, respectively. Crumb quality value is affected by flour quality at a level of 35.5%; much more influenced are other ingredients, fibers and gluten as well as pH value during chemical treatment of fibers.
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N. Filipovic et al. / Journal of Food Engineering 78 (2007) 1047–1053 5 0 .9 5 4
4. 1
1. 4
Gluten, %
1. 9 3
2. 3 2 2. 7
Crumb quality Modified fibers, pH=7
3. 2
1 3. 7 0 0
2
4
6
8
10
12
14
16
Fibers, %
5
5 3. 1
4
3. 4
Crumb quality Modified fibers, pH=11
2. 7
3. 6
Gluten, %
4. 6
Gluten, %
4. 5 4
3 3. 8 4. 1 2
3. 2
2
Crumb quality Modified fibers, pH=3.5
4. 3
1
3
3. 7 4. 1
1
1. 9
2. 9
2. 3
0
1. 4
0 0
2
4
6
8
10
12
14
16
0
2
4
6
Fibers, %
8
10
12
14
16
Fibers, %
Fig. 4. Bread crumb quality as a function of modified fibers and gluten quantity.
Table 3 Significance of parameters in the model (1) for non-modified fibers
Table 4 Significances of parameters in the model (2) for modified fibers
Significance, %
Significance, %
Flour Other ingredients Total
Dough yield
Bread yield
97.0 3.0
96 4
84 16
100
100
100
Bread volume
Bread crumb 61.5 38.5 100
Other ingredients Linear single factor Fibers Gluten
74 0.5
63 13.5
20 39
46 7
Interaction of factors Fibers and gluten
25.5
23.5
4
43
37
4
100
100
Quadratic single factor Fibers
–
–
Total
100
100
However, when the ingredients (added to the flour) are compared, following conclusions can be drawn. Both yields are very similar in functions with fibers and gluten. On the contrary, the influence of the pH value is much greater in the case of bread yield (14% + 17% = 31%) than in the case of dough yield (18% + 2% = 20%). The volume of bread depends significantly on gluten quantity (24%) and its interaction with fibers (15%) and pH value of fibers treat-
Bread yield
Bread volume
Bread crumb
84 16
75 25
68.5 31.5
35.5 64.5
100
100
100
100
Other ingredients Linear single factor Fibers Gluten pH
26 13 18
22 9 14
18 24 8
13 3 27
Interaction of factors Fibers and gluten Fibers and pH Gluten and pH
1 16.5 10
1 17 9
15 9 12
0.5 14 1.5
Quadratic single factor Fibers pH
13.5 2.0
11 17
4 10
12 29
100
100
100
Flour Other ingredients Total
Total
Dough yield
100
ment (12%). The quantity of fibers themselves shows its affect at a level of 18% + 4% = 22%. Finally, it seems that crumb quality depends almost only on pH value of chemical process (27% + 29% = 56%). Also, fibers (13%) and fibers interaction with pH value (14%) are important.
N. Filipovic et al. / Journal of Food Engineering 78 (2007) 1047–1053
4. Conclusion The aim of this investigation was to determine the effect of non-modified and modified fibers from sugar-beet pulp on yield of dough and bread, bread volume and crumb quality, by experimental work and mathematical considerations. Based on the obtained results following conclusions can be drawn. Chemical composition of flour, used as a raw material in bread production, has a great influence on all product characteristics. According to mathematical model, both yields are highly affected by flour quality, many times higher than by other ingredients. However, this conclusion drastically changes when the modified fibers have been applied. The enrichment of the product with non-modified fibers increases yield of dough and bread and decreases bread volume and crumb quality. From the statistical point of view, the most significant independent variable proved to be the quantity of fibers. Gluten affects positively all the investigated characteristics. When modified fibers are applied, trends in changes of product characteristics do not change. Namely, the yield of dough and bread increases, while volume and crumb quality decreases, with the increase of fibers quantity. In a majority of analysed cases, the most significant independent variable proved to be the quantity of fibers. The volume of bread depends significantly on the quantity of gluten and its interaction with fibers. However, an introduction of a new variable (pH value during chemical treatment of fibers) introduces new effects and their consequences to product characteristics. This became particularly evident in the case of crumb quality the value of which depends almost only on pH value of chemical process. The comparison between non-modified and modified fibers gives the advantage to the non-modified fibers from two aspects: (i) decrease of product quality is less in the case of non-modified fibers and (ii) non-modified fibers are not exposed to any chemical treatment, which must be less expensive. Therefore, the enrichment of bread with less than 10% of non-modified fibers, accompanied with a few percents of gluten, is highly recommended. Acknowledgements The authors thank the Ministry of Science and Technology, Republic of Serbia for the support. References Abdul-Hamid, A., & Siew Luan, Y. (2000). Functional properties of dietary fibers prepared from defatted rice bran. Food Chemistry, 68, 15–19. Anderson, J. W. (1991). Lipid responses of hypercholesterolemic men to oat-bran intake. American Journal of Clinical Nutrition, 54, 678–683. Asp, N.-G. (2004). Definition and analysis of dietary fibers in context of food carbohydrates. In J. W. van Kamp, N.-G. Asp, J. Miller Jones, & G. Schaafsma (Eds.), Dietary fibers bio-active carbohydrates for food
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The effect of the type and quantity of sugar-beet fibers on bread characteristics Nada Filipovic *, Mirjana Djuric, Julianna Gyura Faculty of Technology, Carbohydrate Food Technology, Bul. Cara Lazara 1, 2100 Novi Sad, Serbia and Montenegro Received 23 June 2005; accepted 19 December 2005 Available online 28 February 2006
Abstract The application of fibers from various sources in food production is increasing due to their beneficial effects on human health. The aim of this paper is to investigate the effects of non-modified and modified sugar-beet fibers on dough and bread yield, bread volume and bread crumb quality. Dry sugar-beet fibers were ground, sieved through a laboratory sieve and a fraction with particles less than 95 lm was used for further treatment. It was hydrated for 24 h and pressed for removing excess water. In such a way, hydrated but non-modified fibers were obtained. Part of the non-modified fibers was exposed to a further treatment with H2O2, at the pH values: 3.5, 7 and 11 for the additional 24 h. Treated blends were neutralised, washed with tap and distilled water, pressed and blended to a homogenous mass with fine particles. In such a way modified fibers were obtained. Dough and bread were made from white flour, powdered vital gluten, salt and yeast (as it is used in regular bread production), without fibers, with non-modified fibers and with modified fibers. Experiments were planned so that the quantity of the applied fibers in the blends varied from 0% to 15%, while gluten quantity varied from 0% to 5%. Controlling characteristics of the product were: yield of dough and bread, volume, crumb quality. By applying the regression analysis method on the measured data, mathematical models for both fibers application were defined. Based on the experimental results as well as on the mathematical considerations following conclusions were drawn: increase of content of both fibers (non-modified and modified) increases yield of dough and bread but decreases volume of bread and bread crumb quality. On the other hand, increase of gluten quantity increases the volume of bread at small amounts of fibers; when fibers quantity increases, gluten proved ineffective. By the comparison of non-modified and modified fibers, the advantage is given to the non-modified fibers. An enrichment of bread with less than 10% of non-modified fibers, accompanied with a few percents of gluten, is highly recommended. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Bread; Sugar-beet fibers; Mathematical modelling
1. Introduction Products enriched with fibers from various sources can be considered as functional food, satisfying claims cited by Berghofer (2000), particularly when made of natural substances and when consumed every day. Such products contribute to specific metabolic pathways in an organism
*
Corresponding author. Tel.: +381 21 6350 122; fax: +381 21 450 413. E-mail address: nfi[email protected] (N. Filipovic).
0260-8774/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2005.12.050
(Seibel, 1998), causing positive effects to human health. Consumption of food rich in fibers can weaken or even prevent some diseases. Many years ago, a decrease of risk of colon cancer with an increase of intake of fibers-rich food was noticed (Whitehead, 1986). Also, diabetes incidences and hart-related problems can be reduced (Wang, Rosell, & Benedito de Barber, 2002). This must be related to the beneficial effects of fibers on the reduction of cholesterol level (Anderson, 1991). It is very well known that fibers possess dietary character. Not enzymatically degraded within the human digestive tract, fibers can have dietary role and can help in solving some digestive problems
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(Guillon, Auffret, Robertson, Thibault, & Barry, 1998; Wang et al., 2002). Food with high content of fibers causes hunger alleviating effect and, at the same time, does not cause binding minerals like calcium, magnesium and zinc (Stauffer, 1993; Westenhoefer, 2001). The recommendations for dietary fibers intake range from 25 to 30 g day1 (Asp, 2004, Chapter 1; USDA, 2002). On the other hand, bakery products, particularly bread, take a significant share in the food guide pyramid for daily food choices recommended by US Department of Health and Human Services. Therefore, the development of enriched bread with higher fibers content is one of the efficient ways to increasing the fibers intake (Goesaert et al., 2005; Sangnark & Noomhorm, 2004; Wang et al., 2002). The main source of fibrous materials, which can be incorporated into bakery products, is cereal bran, particularly wheat bran (Lai, Hoseney, & Davis, 1989; Ranhotra, Gelroth, Astroth, & Posner, 1990; Sidhu, Al-Hooti, & Al-Saqer, 1999) but also rice bran (AbdulHamid & Siew Luan, 2000). However, bran has a low water retention capacity and is adversely affecting crumb colour. So, investigations need to be directed toward other possible sources, including sugar-beet. In sugar-beet technology, pulp is remaining after sugar extraction as a waste product. Favourable sensory, physical and chemical characteristics, as well as microbiology, qualify this material as a valuable source of dietary fibers (Basman & Ko¨ksel, 1999; Persson, 1986). In comparison with cereal bran, sugar-beet fibers are characterized: (i) by low phytate, which is of particular concern to nutritionists because of its possible adverse effects on mineral absorption (Graf, 1986) and (ii) by better water binding and retention capacity, which is of particular interest for the baking industry (Stauffer, 1993). A wide range of research activities is related with the adjustment of fibers characteristics, by grinding (Auffret, Ralet, Guillon, Barry, & Thibault, 1994), by chemical treatment (Jasberg, Gould, Warner, & Navickis, 1989; Renard, Cre´peau, & Thibault, 1994) and by other methods. Very often, adjustments are undertaken in order to meet consumers’ preferences for white or light coloured bread. The aim of this investigation is to recommend optimal quality and quantity of sugar-beet fibers, which will guarantee satisfactory yield of dough, yield of bread, bread volume and crumb quality.
2.2. Methods Chemical composition (dry matter, proteins, mineral matters) of fibers was determined according methods specified by Reinefeld and Schneider (1983). 2.2.1. Water holding capacity of dietary fibers 2.5 g of dried ground fibers were suspended in 30 cm3 of distilled water at 30 °C in a centrifuge glass tube of 50 cm3 and thermostated for 30 min at 30 °C. Every 10 min the suspension was homogenized by stirring. The suspension was centrifuged at 5000g for 5 min and the swollen fibers particles were separated from the supernatant and weighed. The water holding capacity of the fibers was calculated from the difference between the hydrated (swollen) and dried sample (Stauffer, 1993). 2.2.2. Non-modified fibers The fibers after 60 min extraction of sugar-beet cossettes with sulphurous acid at 75 °C and pH = 5.7 are considered to be non-modified fibers. After drying at 80 °C fibers were ground in a Falling Number laboratory mill, type 3100, sieved through a laboratory sieve and a fraction with particles less than 95 lm were used for further treatment. Prior dough mixing, these types of fibers were hydrated for 24 h (ratio fibers to water = 1:4) at room temperature. 2.2.3. Modified fibers Prior to grinding non-modified fibers were hydrated for 24 h (ratio fibers to water = 1:9) at room temperature, then pressed in a laboratory press to remove excess water. After pressing they were treated with H2O2 up to blend concentration of 20 g L1 H2O2 and pH = 3.5. For treatments at neutral and alkaline media pH from 3.5 was adjusted to 7 and 11 with 10 M NaOH. After this 24 h chemical treatment, blends were neutralised with cc HCl until the pH reached the value 6–7 in all cases. Chlorine ions were washed with tap and distilled water to reach negative reaction to Cl ions. Modifies fibers were pressed to remove the excess water and blended to a homogenous mass with fine particles in a Braun blender.
2.1. Materials
2.2.4. Fibers determination Non-soluble fibers were determined according to AOAC Official Method 991.42 Insoluble Dietary Fibers in Foods and Food products Final Action 1994. Soluble fibers were determined according to AOAC Official Method 993.19 Soluble Dietary Fibers in Foods and Food products Final Action 1996.
Sugar-beet cossettes, safe product concerning heavy metals and microbiology (Gyura, Filipovic´, Sˇkrbic´, Sˇeresˇ, ˇ upic´, 2003), were used. &C White flour (ash and protein content 0.53 and 11.2% d.m. basis, respectively), powdered vital gluten (protein content 76% d.m. basis), salt and yeast were of commercial grade, as it is used in regular bread production.
2.2.5. Baking procedure Bread was baked according to the AACC method. Dough constituents were: flour (100–85%), sugar-beet fibers (0–15%), salt (2%), yeast (2.5%) and gluten powder (0–5%). Bread was baked approximately 15 min in a Chopin laboratory oven at 260 °C, until the mass of baked bread ranged between 135 and 137 g. The quality of bread
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was characterised by dough yield, bread yield, bread volume and crumb quality. 3. Results and discussion 3.1. Results obtained by measurements The composition of fibers is presented in Table 1. The fibers modification by hydrogen peroxide contributes to significant increase in water holding capacity and favourable ratio of soluble to insoluble fibers. Treatment by hydrogen peroxide diminished fibers offcolour which is illustrated in Fig. 1. This decolourization effect enables fibers supplementation into white flour bread without adverse contribution to crumb and crust colour. Characteristics of bread made without fibers as well as with non-modified and modified fibers are given in Table 2. Each value represents mean of not less than 5 and not greater than 10 replicates and could be assumed reliable. It is obvious that the quantity of the applied fibers in the blends varied from 0% to 15%, while gluten quantity varied from 0% to 5%. Experiments proved that the quantity of fibers should not exceed 15%, due to extreme decrease of dough and bread characteristics with the increase of fibers content, while quantity of gluten should not exceed 5%, for the highest level of gluten causes poor mouth-feel of bread. A comparison between characteristics of non-fibers product and products with non-modified and modified fibers (in Table 2) shows that yields of dough and bread tend to increase with the increase of fibers quantity while, at the same time, volume of bread as well as crumb quality tend to decrease with the increase of fibers quantity. The
Table 1 Composition of non-modified and modified fibers Parameters
Non-modified fibers
Modified fibers
Dry matter content, % Water holding capacity, % Total fibers, % d.m. basis Insoluble fibers, % d.m. basis Soluble fibers, % d.m. basis Proteins, % d.m. basis Mineral matters, % d.m. basis
91.8 620 70.00 57.80 12.20 12.30 2.50
97.6 1596 94.33 61.12 33.21 4.16 9.42
Fig. 1. The colour of sugar-beet fibers: non-modified, modified, modified and fine mashed (from left to right).
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last conclusion might be explained by a weakening of gluten matrix, which is losing the ability to retain gases created during fermentation in the presence of fibers. Insufficient formation of gluten network influence dough handling that can be improved by adding gluten enhancing material like here applied vital gluten. However, gas retention is affected by the incorporated fibers quantity. As for the difference between effects of non-modified fibers and modified fibers on product characteristics, it seems that non-modified fibers should be given an advantage, if taking both volume of bread and crumb quality as the objectives and if analysing blends with gluten as improver. The comparison of the modified fibers, among themselves, from the same point of view, shows negligible difference between the fibers modified at pH = 3.5 and pH = 11, particularly in the case when the quantity of fibers does not exceed 10%. The fibers treated at pH = 7 proved acceptable when added at higher quantities, having in mind bread volume. However, their influence on crumb quality is improper. The relationship between fibers type’s, fibers quantity and gluten quantity, on one hand, and the product characteristics, on the other, became more evident after a graphical presentation of the results from Table 2. In the case of non-modified fibers application, 3-D diagrams of the important product characteristics (bread volume, and crumb quality) were presented in Fig. 2. An analysis shows that an increase of fibers content decreases volume of bread. On the other hand, the increase of gluten quantity increases volume of bread at small amounts of fibers; when fibers quantity increases, gluten proved ineffective. Similar conclusions can be drawn when crumb quality is analysed. In the case when modified fibers are applied, 3-D diagrams in Fig. 3 show that all three systems obey the same type of function and that the differences among fibers effects the bread volume almost negligibly. Quite contrary, when crumb quality is analysed (Fig. 4), great differences among fibers are found; the best are fibers treated at pH = 3.5, followed by fibers processed at pH = 11, while fibers obtained at pH = 7 decrease crumb quality by an unacceptable value. 3.2. Results obtained by mathematical modelling In order to obtain statistical approval of the conclusions above, the results from Table 2 were used in the regression analysis procedure and two mathematical models, for each particular characteristic, were derived: (i) the first one covers the case of enrichment with non-modified fibers and (ii) the second one deals with the case of modified fibers. In both cases a polynomial was chosen as a type of the regression, in accordance with the applied plan of experiments (Table 2). So, when non-modified fibers are applied a mathematical model, which proved the best, is given by Eq. (1): y ¼ b1 þ b2 x1 þ b3 x2 þ b4 x1 x2 þ b5 x21
ð1Þ
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Table 2 Measured values of dough and bread characteristics No
Fibers quantity, %
Gluten, %
Fibers modification, pH value
Dough yield, g
Bread yield, g
Bread volume, ml
Bread crumb quality, min = 0; max = 7
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
0 5 10 15 5 10 15 5 10 15 5 10 15 5 10 15 5 10 15 5 10 15 5 10 15
0 0 0 0 5 5 5 0 0 0 5 5 5 0 0 0 5 5 5 0 0 0 5 5 5
– – – – – – – 3.5 3.5 3.5 3.5 3.5 3.5 7 7 7 7 7 7 11 11 11 11 11 11
167.3 170.4 170.9 173.9 170.6 173.6 176.6 176.3 179.4 182.4 179.1 182.1 185.1 168.3 171.2 172.3 170.9 176.9 179.9 172.3 172.6 175.6 172.3 175.3 172.6
140.7 143.4 143.9 147.6 145.0 148.4 151.6 151.3 155.5 159.6 155.2 159.3 163.8 143.1 146.2 147.5 143.8 151.5 155.9 147.5 147.9 150.1 147.5 149.9 147.9
290 280 220 180 305 260 210 270 210 160 290 220 170 240 200 175 260 235 190 270 235 205 290 235 180
4.5 3.2 1.2 0.0 4.6 2.8 3.0 4.2 3.5 2.4 4.6 3.7 2.9 2.0 1.0 0.5 2.8 2.0 0.7 3.9 2.5 0.5 4.0 3.0 2.5
5
5 29 2
4
4. 5
22 2
30 6
Crumb quality Non-mod. fibers
4
23 6
2. 4
Gluten, %
Gluten, %
25 0 3
26 4 2
3
2. 9
2 3. 4
27 8
Volume, mL
1
20 8
4. 0
1
Non-mod. fibers
1. 9
19 4
0 .8 0 1. 3
0
0 0
2
4
6
8
10
12
14
16
0
2
4
6
Fibers, %
8
10
12
14
16
Fibers, %
Fig. 2. Bread volume and crumb quality as the functions of non-modified fibers and gluten quantity.
In the model (1), b’s are parameters, x1 signifies fibers quantity and x2 is gluten quantity while y denotes product characteristic. Parameter b1 corresponds to y in the case when x1 = x2 = 0, which means that b1 represents corresponding characteristic of dough and bread made from flour without other ingredients. The second and third terms represent the impact of single variable (fibers quantity and gluten quantity) on the product characteristics, the fourth term introduces a coupled effect of fibers and gluten while the last, the fifth term expresses quadratic effects of fibers quantity, giving highly non-linear character to the relationship (1).
Alternatively, the enrichment with modified fibers is modelled by Eq. (2): y ¼ b1 þ b2 x1 þ b3 x2 þ b4 x3 þ b5 x1 x2 þ b6 x1 x3 þ b7 x2 x3 þ b8 x21 þ b9 x23
ð2Þ
In the case when fibers are chemically treated, an additional variable (denoted as x3) should be introduced in the model. Through this variable, the influence of pH value of the chemical treatment on the product quality has been taken into account. Polynomial (2) contains also the parameter b1 the meaning of which is the same as in the
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5 304 4
208 28 8
Gluten, %
224 3
240 2 256
1 92
Volume, mL Modified fibers, pH=7
1 2 72 0 0
2
4
6
8
10
12
14
16
Fibers, %
5
5 192
4
30 4
208 4
208
306
222 236
G lut en, %
Gluten, %
224 3 240 256 2
Volume, mL
272
3 250 264 2 292
Volume, mL
Modified fibers, pH=3.5
1
194
278
1
Modified fibers,pH=11
17 6
288 0
0 0
2
4
6
8
10
12
14
16
Fibers, %
0
2
4
6
8
10
12
14
16
Fibers, %
Fig. 3. Bread volume as a function of modified fibers and gluten quantity.
previous case. The second, third and fourth terms, at the right hand side of the polynomial (2), represent the impact of single variable (fibers quantity, gluten quantity and pH value) on the product characteristics. The fifth, sixth and seventh terms are related to the interaction of: fibers and gluten, fibers and pH value as well as gluten and pH value, representing coupled impact of two variables on the product characteristics. Finally, the eight and ninth terms introduce quadratic effects of a single fibers and single pH value. Applying the regression analysis method to adequate series of data (Table 2), b-parameters were determined (for both mathematical models) and their t-factors were obtained in the same procedure. Each t-factor represents statistical measure of significance of each parameter in the mathematical models. They are presented in Tables 3 and 4 as fractions of 100% for every characteristic of the product. The significances are given twice; in the first part of each Table a difference between the significance of flour, on one hand, and significance of all the other components, on the other hand, is expressed, while in the second part the significances of other components are compared among themselves. In Table 3 significances for the system with non-modified fibers are shown. From the first part of Table 3, it can be concluded that both yields (dough and bread) depend at a level higher than 90% on flour characteristics. Bread volume is affected by flour quality at a level of 84%,
while the remaining 16% is associated with the influence of other ingredients (fibers and gluten). Crumb quality value depends at a level of 61.5% on the quality of flour while 38.5% of influences are related with the added components. Analysis of values from the second part of Table 3, leads to the conclusion that both yields (dough and bread) are linear functions of added components quantities. The yield of dough highly depends on fibers (74%) as well as on fibers interaction with gluten (25.5%); the yield of bread depends on fibers (63%), gluten (13.5%) and their interaction (23.5). The volume of bread and crumb quality are quadratic functions with double effect of fibers, linear and quadratic. Analysis of significances (from Table 2) shows that the fibers’ linear influence (20%) and quadratic influence (37%) on bread volume prevails compared to the influence of gluten (39%). In the case of crumb quality the linear effect of fibers (46%) dominates their interaction with gluten (43%). In Table 4 significances for the system with modified fibers are given. In this case, the yield of dough, the yield of bread and the volume of bread depend on flour characteristics at following levels: 84%, 75% and 68.5%, respectively. Crumb quality value is affected by flour quality at a level of 35.5%; much more influenced are other ingredients, fibers and gluten as well as pH value during chemical treatment of fibers.
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N. Filipovic et al. / Journal of Food Engineering 78 (2007) 1047–1053 5 0 .9 5 4
4. 1
1. 4
Gluten, %
1. 9 3
2. 3 2 2. 7
Crumb quality Modified fibers, pH=7
3. 2
1 3. 7 0 0
2
4
6
8
10
12
14
16
Fibers, %
5
5 3. 1
4
3. 4
Crumb quality Modified fibers, pH=11
2. 7
3. 6
Gluten, %
4. 6
Gluten, %
4. 5 4
3 3. 8 4. 1 2
3. 2
2
Crumb quality Modified fibers, pH=3.5
4. 3
1
3
3. 7 4. 1
1
1. 9
2. 9
2. 3
0
1. 4
0 0
2
4
6
8
10
12
14
16
0
2
4
6
Fibers, %
8
10
12
14
16
Fibers, %
Fig. 4. Bread crumb quality as a function of modified fibers and gluten quantity.
Table 3 Significance of parameters in the model (1) for non-modified fibers
Table 4 Significances of parameters in the model (2) for modified fibers
Significance, %
Significance, %
Flour Other ingredients Total
Dough yield
Bread yield
97.0 3.0
96 4
84 16
100
100
100
Bread volume
Bread crumb 61.5 38.5 100
Other ingredients Linear single factor Fibers Gluten
74 0.5
63 13.5
20 39
46 7
Interaction of factors Fibers and gluten
25.5
23.5
4
43
37
4
100
100
Quadratic single factor Fibers
–
–
Total
100
100
However, when the ingredients (added to the flour) are compared, following conclusions can be drawn. Both yields are very similar in functions with fibers and gluten. On the contrary, the influence of the pH value is much greater in the case of bread yield (14% + 17% = 31%) than in the case of dough yield (18% + 2% = 20%). The volume of bread depends significantly on gluten quantity (24%) and its interaction with fibers (15%) and pH value of fibers treat-
Bread yield
Bread volume
Bread crumb
84 16
75 25
68.5 31.5
35.5 64.5
100
100
100
100
Other ingredients Linear single factor Fibers Gluten pH
26 13 18
22 9 14
18 24 8
13 3 27
Interaction of factors Fibers and gluten Fibers and pH Gluten and pH
1 16.5 10
1 17 9
15 9 12
0.5 14 1.5
Quadratic single factor Fibers pH
13.5 2.0
11 17
4 10
12 29
100
100
100
Flour Other ingredients Total
Total
Dough yield
100
ment (12%). The quantity of fibers themselves shows its affect at a level of 18% + 4% = 22%. Finally, it seems that crumb quality depends almost only on pH value of chemical process (27% + 29% = 56%). Also, fibers (13%) and fibers interaction with pH value (14%) are important.
N. Filipovic et al. / Journal of Food Engineering 78 (2007) 1047–1053
4. Conclusion The aim of this investigation was to determine the effect of non-modified and modified fibers from sugar-beet pulp on yield of dough and bread, bread volume and crumb quality, by experimental work and mathematical considerations. Based on the obtained results following conclusions can be drawn. Chemical composition of flour, used as a raw material in bread production, has a great influence on all product characteristics. According to mathematical model, both yields are highly affected by flour quality, many times higher than by other ingredients. However, this conclusion drastically changes when the modified fibers have been applied. The enrichment of the product with non-modified fibers increases yield of dough and bread and decreases bread volume and crumb quality. From the statistical point of view, the most significant independent variable proved to be the quantity of fibers. Gluten affects positively all the investigated characteristics. When modified fibers are applied, trends in changes of product characteristics do not change. Namely, the yield of dough and bread increases, while volume and crumb quality decreases, with the increase of fibers quantity. In a majority of analysed cases, the most significant independent variable proved to be the quantity of fibers. The volume of bread depends significantly on the quantity of gluten and its interaction with fibers. However, an introduction of a new variable (pH value during chemical treatment of fibers) introduces new effects and their consequences to product characteristics. This became particularly evident in the case of crumb quality the value of which depends almost only on pH value of chemical process. The comparison between non-modified and modified fibers gives the advantage to the non-modified fibers from two aspects: (i) decrease of product quality is less in the case of non-modified fibers and (ii) non-modified fibers are not exposed to any chemical treatment, which must be less expensive. Therefore, the enrichment of bread with less than 10% of non-modified fibers, accompanied with a few percents of gluten, is highly recommended. Acknowledgements The authors thank the Ministry of Science and Technology, Republic of Serbia for the support. References Abdul-Hamid, A., & Siew Luan, Y. (2000). Functional properties of dietary fibers prepared from defatted rice bran. Food Chemistry, 68, 15–19. Anderson, J. W. (1991). Lipid responses of hypercholesterolemic men to oat-bran intake. American Journal of Clinical Nutrition, 54, 678–683. Asp, N.-G. (2004). Definition and analysis of dietary fibers in context of food carbohydrates. In J. W. van Kamp, N.-G. Asp, J. Miller Jones, & G. Schaafsma (Eds.), Dietary fibers bio-active carbohydrates for food
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