Sugar Beet Fiber and Guar Gum Impact Dough Rheological Properties

Hamza Ceylan, Merve Arıbaş, PhD, Özen Özboy Özbaş, Prof.Dr., Aksaray University

Sugar beet fiber (SBF) has been used in food technology as a source of dietary fiber (DF). The incorporation of SBF into cookie, bread, spaghetti, extrusion product, Frankfurter, Turkish-type salami, tarhana has been studied because of its excellent functional and physiological properties.

In food industry, guar gum (GG) is also used as a novel food additive in various food products for food stabilization and as DF source. However, there is limited information available in literatüre on the reological behaviours of SBF and GG in wheat flour-dough systems.

So, the present preliminary study was planned to study the effects of incorporation of SBF and GG on rheological properties of wheat flour.

For rheological analysis, commercial white wheat flour from a local industrial mill (moisture, ash and protein contents were 13.2, 0.72 and 10.5 % d.d., respectively), guar gum and salt were used. Fibrex (F) was a commercial fiber product (including 67% of DF) originnating from sugar-beet (Sweden). Sample of flour and flour blended with F (3%, 6%, 9%) and flour blended with GG (0.5 %, 1%, 1.5 %) were analyzed for rheological characteristics of dough by using Absograph 500 and Resistograph 500 equipments (Bastak Instruments, Ankara, Türkiye). Water absorption (WA, %), development time (DT, min), stability (ST, min) and FQN (farinograph quality number) were determined from the Absograph 500 curves. The parameters obtained from the Resistograph 500 curves were extensibility (Ex, rupture, mm), energy (A, cm²), tensile resistance (Rs, BU), maximum tensile resistance (Rm, BU), ratio of resistance to extensibility (Rs/Ex) and ratio of maximum tensile resistance to extensibility (Rm/Ex) of dough were summarized at 135 min. The Absograph 500 and Resistograph 500 tests were made in duplicate and the mean values are presented in Table 1.

From the Absograph 500, the dough sample where the flour had not been substituted by F and GG had low WA, DT, and FQN with values 63.6%, 0.9 min, and 23, respectively. These parameters varied from 64.7 to 67.5%, 1.0 to 7.8 min, 28 to 110, respectively, and for ST from 2.0 to 8.0 min for the dough samples with F substitution. For the dough samples with GG addition, these values varied from 65.9 to 69.9%, 1.1 to 1.2 min, and 22 to 29, respectively. High WA values for blends of flour and F and GG have also been reported earlier. The substitution of flour with F and GG, independent of the concentration, decreased the ST of dough, while the DT increased with increasing F content when compared to the control and the GG substituted samples. The sample with 6% of F had the highest FQN when compared to the other samples.

From the Resistograph 500 data, dough made with unsubstituted flour (no F or GG) showed characteristics of a weak-medium dough, with resistance to extension at constant deformation (Rs) and extensibility (Ex) of 349 BU and 92 mm, respectively, at the final rest time (135 min). Rs and Ex values ranged from 706 to 742 BU and from 112 to 79 mm, respectively, for the dough samples substituted with F. The values for the same parameters (Rs and Ex) for the dough samples with GG were between 576 to 520 BU and 120 to 124 mm, respectively. The rest time was important for the

Table 1. Rheological parametes1 of wheat flour-F and wheat flour-GG dough

¹ F: Fibrex, GG: Guar Gum, WA: Water Absorption, DT: Development Time, ST: Stability,

  FQN: Farinograph Quality Number, Ex: Extensibility, A: Energy, Rs: Tensile Resistance,

  Rm: Maximum Tensile Resistance, Rs/Ex: Ratio of Resistance to Extensibility,

  Rm/Ex: Ratio of Maximum Tensile Resistance to Extensibility.

higher addition of both F and GG substituted samples, which needed the highest rest time (135 min) in order to reach maximum resistance. The addition of F and GG to wheat flour brought some changes in the dough mixing behaviour as measured by Absograph 500 and Resistograph 500 and these absographic and resistographic characteristics of flour supplemented with F indicate that F supplemented flour can be used for making good quality bread. Results also indicate that incorporation of GG to the wheat flour increased the Ex value.

However, further researches are needed in order to determine the effects of incorporation of different levels of Fibrex and guar gum along with Fibrex on absographic and resistographic characteristics and to understand if Fibrex can be utilized with guar gum for value addition.

Acknowledgements

The authors wish to thank Bastak Instruments (Ankara, Türkiye) for making facilities available for this study. 867 words