RHEOLOGICAL AND TEXTURAL PROPERTIES OF CRACKER DOUGH WITH ADDITION OF PEA DIETARY FIBER INTRODUCTION

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1 RHEOLOGICAL AND TEXTURAL PROPERTIES OF CRACKER DOUGH WITH ADDITION OF PEA DIETARY FIBER Ljubica Dokić 1 *, Biljana Pajin 1, Aleksandar Fišteš 1, Zita Šereš 1, Drаgana Šoronja Simović 1 and Velјko Krstonošić 2 1 University of Novi Sad, Faculty of Technology, Bulevar cara Lazara 1, Novi Sad, Serbia 2 University of Novi Sad, Faculty of Medicine, Hajduk Veljkova 11, Novi Sad, Serbia Consumers are becoming aware of health benefits of dietary fiber intake. In past years, the development of products containing different fiber is increasing. The aim of this research was to look into the effect of addition pea fiber to dough for crackers. Rheological and textural properties were evaluated. In order to develop dough in which wheat flour was partly substituted with pea fiber, it was necessary to increase water content. The addition of 5% and 10% of pea fiber affected intramolecular linkages of gluten and lowered elastic properties of the dough. Dough with addition of 30% of fiber was brittle, grainy and impossible to process. KEY WORDS: dietary fiber, rheology, texture, dough INTRODUCTION Dietary fibers relate to a heterogeneous group of components with different functional properties. The fibers swell in aqueous media of intestinal juices, absorb water and small molecules. Between the fibers and the molecules that surround them, different types of bonds are formed, such as ionic, hydrogen, weak hydrophobic bonds and dispersion forces, which may influence the absorption of minerals and steroids (1,2). Numerous studies show that the consumption of fibers protect against heart disease and cancer, normalize the lipid content in the blood, affect the glucose level and insulin secretion, prevent the constipation and digestive tract diseases (3,4). The enrichment of food with dietary fibers aims to increase the dietary fibers intake. It is mainly done in case if bakery products, cookies, crackers, and other products that may contain cereals have been done. However, as a source of fibers, different by products of milling of wheat, maize, sorghum and other cereals can be used, as well as the products obtained by wet milling of corn and wheat. There are many other potential sources of fibers, such as fruits, vegetables, and infrequently used grains (5,6). Soluble dietary fibers, including pectin and hydrocolloids are found in fruits, nuts, vegetables, legumes (7). Insoluble fibers, including cellulose and hemicelluloses, may be found in whole grain cereals. Dietary fibers from cereals include 50% of all sources, % is obtained from vegetables, * Corresponding author: Ljubica P. Dokić, University of Novi Sad, Faculty of Technology, Bulevar cara Lazara 1, Novi Sad, Serbia, ldbaucal@tf.uns.ac.rs 29

2 about 16% are of the fruit, and the remaining 3% is from other sources of dietary fibers (8). The important technological characteristics of dietary fiber that determine the possibilities for their application are water holding capacity, capacity of fat binding, viscosity, gel forming ability, chelating capacity, and the influence on food texture. The water holding capacity is associated with the length and density of the fibers. Also, the ph of the environment affects the water retention capacity. Capacity of fat binding is more dependent on the porosity of the fibers, than the molecular affinity. Fibers such as pectin, gums and β-glucan form solutions with large viscosity, and they are commonly used as thickeners (9). Viscosity of insoluble and some soluble fibers, such as inulin, is minimal. The ability to form a gel is the most important feature in using fibers as a fat replacer. This ability is provided by cross-linking of polymeric units and by retention of water or other solvents in the gel structure. This characteristic depends on a number of factors, such as concentration, temperature, the presence of certain ions, and the ph of the environment. The objective of this study was to determine the rheological and textural properties of dough for crackers with addition of pea dietary fibers. EXPERIMENTAL Materials Materials used in cracker formulation were wheat flour (type T-500, Danubius, Novi Sad, Serbia) pea dietary fiber (EF150, J. Rettenmaier & Son, Rosenberg, Germany), vegetable fat (Dijamant, Zrenjanin, Serbia), yeast, leavening agent NaHCO 3, NaCl and water. Methods Alkaline water retention capacity (AWRC) of wheat flour and wheat flour-pea fiber mixtures was determined according to AACC method (10). Dough preparation: The control sample contained only wheat flour. The wheat flour was substituted at the levels of 5, 10 and 30% by pea dietary fibers, to produce dietary fibers containing samples. The dough for crackers was prepared according to the long fermentation process. The process includes two phases: mixing of the sour dough and mixing of dough in the vertical spindle mixer. The dough for cracker is of soft consistency, with 30% of moisture. The sour dough contained wheat flour (70% of total amount of flour), yeast (0.4%) and water (30%). The mixing time was 10 min at 27 o C, and the fermentation process was 18 h at relative humidity of 80-90%. The dough contained wheat flour (30% of total amount of flour), vegetable fat (11%), NaCl (1.5%) and NaHCO 3 (1.0%). The ingredients for the dough were added to sour dough and mixed for 5 min. The second fermentation process was 5 h at o C and relative humidity of 80-90%. After the second fermentation, rheological and textural measurements were performed. 30

3 Rheological properties: Rheological properties of cracker dough were determined using a rotational viscometer HAAKE RheoStress RS600 (Thermo Electron Corporation, Karlsruhe, Germany) with plate plate sensor PP60 Ti (plate diameter was 60 mm and gap 1 mm). The measurements were done at 27±0.1 o C. Viscoelastic properties of the dough, defined by storage modulus (G') and loss modulus (G"), were determined by dynamic oscillatory measurements in the range of linear viscoelastic regime (LVE). The moduli were observed during increased frequency from 1 to 10 Hz, and at constant shear stress of 10 Pa. The results were expressed as value tan δ = G"/G'. Viscoelastic response of the samples at a constant stress, as well as the sample behavior after removing the stress, were determined by creep and recovery test. The test was performed in the LVE regime in which the deformation amplitude was proportional to the applied stress amplitude. The creep time with constant stress (σ=10 Pa) was 150 s, and the recovery period after removing the stress was 300 s. The creep data were analyzed by the Burger's model [1]. J(t) = J 0 + J 1 (1-exp(-t/λ)) + t/η 0 [1] For the recovery phase, the equation of the Burger's model is [2]. J(t) = J max J 0 J 1 (1-exp(-t/λ)) [2] The value J 0 is the instantaneous compliance, J 1 is the retarded (viscoelastic) compliance, J max is the maximum compliance, λ is the mean retardation time, and η 0 is the Newtonian viscosity. Also, the relative elastic part J e /J max and relative viscous part J v /J max of the maximum creep compliance were determined from creep and recovery curves. Textural properties: Textural properties of the dough for crackers were determined on a Texture Analyzer TA.HD Plus (Stable Micro Systems, Godalming, U.K.). Hardness of the dough was determined by penetration test using the cylindrical element (P/6) 6 mm in diameter. Extensibility was determined by the method specified by the device producer, Extensibility of dough and measure of gluten quality. The load cell of 5 kg was used. RESULTS AND DISCUSSION Alkaline water retention capacity is a parameter by which quantity of water needed to obtain optimal consistency of dough is calculated. For the control dough, 30.59g of water was added. The AWRC values for the examined samples are given in Table 1. Since pea flour is a typical hydrocolloid macromolecule its water retention capacity is high, and increases the AWRC values of flour mixtures compared to wheat flour. Due to this effect, the increase in water content in order to develop dough was necessary. Water quantities added to flour mixtures were 45.51g, 50.44g and 73.47g for the mixtures containing 5%, 10% and 30% of pea dietary fiber, respectively. Even though water quantity was increased when wheat flour was replaced with 30% of pea fiber, the presence of fiber resulted in so high colloidal bonding of water that the obtained dough was brittle, grainy and un- 31

4 able to stretch, so that measurements were not possible to perform. Hence, the measurements were done and rheological and textural properties determined only for the samples containing 5% and 10% of pea fiber. Table 1. AWRC of wheat flour, pea dietary fiber and flour-pea dietary fiber mixtures Sample Wheat Mixture Mixture Mixture PF flour 5%PF 10%PF 30%PF AWRC (%) PF-pea dietary fiber The viscoelastic properties are presented in Figure 1. As expected, the elastic modulus is higher than the viscous one, since the dough is a highly viscoelastic system. Due to the hydrocolloid nature of the pea fiber and water bonding, the elastic modulus of the dough with 5% of pea fiber was higher than of the control. On the contrary, the dough with 10% of pea fiber had lower value compared to the control sample. Replacement of wheat flour with pea fiber in the dough formulation resulted in a lower gluten content, which was replaced with non-stretchable cellulose as the main component of the pea fiber G', G'' (Pa) f (Hz) G' control G'' control G' 5% PF G'' 5% PF G' 10% PF G'' 10% PF 32 Figure 1. Elastic (G`) and viscous (G``) moduli of dough The calculated values of the tanδ were 0.432, and for the control, 5% PF and 10% PF, respectively. Such values of tanδ are characteristic for amorphous polymer systems. The creep and recovery tests were performed, and the parameters are given in Tables 2 and 3. Under the constant stress, applied in the linear viscoelastic region, which does not disrupt sample structure intermolecular bonds, are starched and deformed. The resulting

5 value of J 0 (instantaneous compliance) is the result of elastic deformations, while retarded compliance J 1 is a result of viscoelastic deformations. The control sample in which gluten content was the highest had the highest elastic instantaneous compliance, i.e. elastic deformation. The intramolecular disulfide bonds between the gluten molecules are highly stretchable. Replacement of protein molecules with rigid cellulose ones resulted in a significant decrease in J 0. When flour is replaced with pea fiber, the decrease in J max implies that the obtained material possesses greater resistance to deformation than the control. The flour upon the addition of fiber becomes stronger. But, increased addition of water to the dough with dietary fiber increased the viscous component η 0. Table 2. Creep phase parameters Creep phase Sample J 0 J 1 η 0 λ 1 J max r (x10 5 ) [Pa -1 ] (x10 4 ) [Pa -1 ] (x10-5 ) [Pas] [s] ( x10 5 ) [Pa -1 ] Control % PF %PF After the removal of the stress, in the recovery phase, one part of deformation remains to represent the viscous part (J v ) of the maximum compliance, whereas the recovery represents the total elastic component (J e ) of the maximum compliance. The values of the relative elastic part J e /J max and relative viscous part J v /J max of the sample maximum compliance were calculated from the recovery curve. The elastic recovery reflects the extent of bonding between the structural elements of dough. The increase in the elasticity means less deformation of the components network in the presence of the fiber, as noticed by other authors with different fiber (11). Table 3. Recovery phase parameters Recovery phase Sample J 0 J 1 η 0 λ 1 r Ј e /Ј max (x10 5 ) [Pa -1 ] (x10 5 ) [Pa -1 ] (x10-6 ) [Pas] [s] Control % PF %PF Texture analysis was performed in order to determine the behavior of the dough in case of large deformations. These tests are useful in getting information on the behavior in processing under the real production conditions. The results are given in Table 4. The values of the hardness, resistance to extension and extensibility, decreased with the addition of pea fiber. Such behavior was also reported by other authors (12). Increased addition of water did not improve the dough ability to stretch, since the excessive water was tightly bonded to cellulose fibers. Such dough should be harder to laminate into thin dough sheets in creacker production. This is the reason why the dough with 30% of pea fiber was unable to produce. 33

6 Table 4. Penetration and extensibility parameters Sample Hardness (g) Resistance to extension (g) Extensibility (mm) Fmax sr ±SD F sr ± SD X sr ± SD Control ± ± ±0.74 5% PF ± ± ± %PF ± ± ±1.17 CONCLUSION Substitution of wheat flour with pea dietary fiber is possible, but dynamic oscillatory parameters, creep recovery test and textural properties showed that the addition of pea fiber increased the stiffness, resistance to deformation, flowability and elasticity of the dough. Acknowledgement This research is conducted within the project Cookies and crackers with functional characteristics aimed for consumers with special dietary needs, supported by the Provincial Secretariat for Science and Technological Development of Vojvodina. REFERENCES 1. Kay R. M. Dietary fiber, J. Lipid Res. 1982, 23, Borderias, A.J; Sanchez-Alonso, I; Perez-Mateos, M. New Applications of Fibres in Foods: Addition to Fishery products, T. Food Sci. Tehn. 2005, 16 (10), Marllet, J.A; McBurney, M.I; Slavin, J.L. Health implications of dietary fiber, J. Am. Diet. Assoc. 2002, 102 (7), Slavin, J.L. Dietary fiber and body weight, Nutrit. 2005, 21, McKee, L.H; Latner, T.A. Underutilized sources of dietary fiber: A review, Plant Foods Hum. Nutr. 2000, 55, Masoodi, F.A; Sharma, M; Chauhan, G.S. Use of apple pomace as a source of dietary in cakes, Plant Foods Hum. Nutr. 2002, 55, Grigelmo-Miguel, N; Gorinstein, S; Marton-Belloso, O. Characterisation of peach dietary fibre concentrate as a food ingredient, Food Chem. 1999, 65, Mezger, T. The Rheology Handbook: For users of rotational and oscillation rheometers", VincentzVerlag., Hannover, 2002, pp Lazaridou, A; Duta, D; Papageorgiou, M; Belc, N; Biliaderis, C.G. Effects of hydrocolloids on dough rheology and bread quality parameters in gluten-free formulations. J. Food Eng. 2007, AACC, Approved methods of the AACC (10 th ed), American Association of Cereal Chemists, st. Paul,MN,

7 11. Skendi, A; Papageorgiou, M; Biliaderis, C.G. Effects of barley β-glucan molecular size and lavel on wheat dough rheological properties. J. Food Eng. 2009, Rouille, J; Della Valle, G; Lefebvre, J; Sliwinski, E; van Vliet, T. Shear and extensional properties of bread dough affected by their minor components. J. Cereal Sci. 2005, РЕОЛОШКЕ И ТЕКСТУРАЛНЕ ОСОБИНЕ ТЕСТА ЗА КРЕКЕРЕ СА ДОДАТКОМ ВЛАКАНА ГРАШКА Љубица Докић 1, Биљана Пајин 1, Александар Фиштеш 1, Зита Шереш 1, Драгана Шороња Симовић 1, Вељко Крстоношић 2 1 Универзитет у Новом Саду, Технолошки факултет, Булевар цара Лазара 1, Нови Сад, Србија 2 Универзитет у Новом Саду, Медицински факултет, Хајдук Вељкова 11, Нови Сад, Србија У скорије време, свест потрошача о корисном здравственом дејству прехрамбених влака расте. Из тог разлога све већи број производа на тржишту који у свом саставу имају повећан садржај влакана. Последњих година, почела је производња прехрамбених влакана из мање познатих сировима, као што су махунарке. У овом раду испитиван је утицај додатка прехрамбених влакана грашка на реолошке и текстуралне карактеристике теста за производњу крекера. Пшенично брашно у формулацији за крекере је замењено са 5%, 10% и 30% влакана грашка. Да би се могло формирати тесто, на основу одређене моћи задржавања воде дефинисана је количина воде коју је потребно додати у замес. Додатком влакана потребно је повећати количину воде у односу на контролни узорак. На основу реолошких и текстуралних мерења утврђено је да се еластичност теста са додатком влакава смањила. Тесто са 30% влакана се лако кидало и било ситнозрнасто, тако да се није могло развући те ова количина влакана није погодна за производњу крекера. Кључне речи: прехрамбена влакна, реологија, текстура, тесто Received: 15 June Accepted: 23 September

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