Tamara Dapčević Hadnađev

Influence of Buckwheat Flour and Carboxymethyl Cellulose on Rheological Behaviour and Baking Performance of Gluten-Free Cookie Dough

In the present study, the influence of buckwheat flour and carboxymethyl cellulose (CMC) on the production of sheetable gluten-free cookie dough of acceptable rheological properties and subsequently their effect on the quality of gluten-free cookies was studied. The buckwheat flour was used to replace 10, 20 and 30 % of rice flour in gluten-free formulations. Cookie doughs of 100 % rice flour and 100 % wheat flour served as control samples. The impact of CMC addition was examined on formulation containing 20 % of buckwheat flour. Oscillatory and creep measurements were applied to test the effect of buckwheat flour and CMC on the viscoelasticity of gluten-free cookie dough. Frequency sweep results showed that all samples had solid elastic-like characteristics. An increase in the buckwheat flour addition led to a decrease in storage modulus and zero shear viscosity and an increase in tan δ and maximum creep compliance, while the addition of CMC led to an increase in dough tenacity and resistance to deformation. Cookie dough containing 30 % of buckwheat flour expressed the highest viscous properties, as revealed by relative viscous compliance value. The gluten-free dough containing CMC and buckwheat flour between 20 and 30 % replacement level showed similar strength and extensibility as wheat cookie dough. The results of the physical and sensory evaluation of gluten-free cookies showed that buckwheat addition led to a decrease in cookie hardness and fracturability and an increase in eccentricity (deformation from regular shape) as well as the overall acceptability, as evaluated by untrained panellists.

Characterization of Byproducts Originating from Hemp Oil Processing

Valorization of hemp seed meal, a byproduct of hemp oil processing, was performed by measuring the distribution of nutritional and antinutritional compounds in different hemp seed meal fractions. According to chemical composition, two cotyledon-containing fractions (>180 and <180 μm) were significantly richer in protein (p < 0.05) (41.2% ± 0.04% and 44.4% ± 0.02%, respectively), lipid (15.1% ± 0.02% and 18.6% ± 0.04%, respectively), and sugar content (4.96% ± 0.11% and 3.46% ± 0.08%, respectively) in comparison to the hull-containing fractions (>350 and >250 μm), which were significantly richer in crude fiber content (29.5% ± 0.04% and 21.3% ± 0.03%, respectively). The free radical scavenging capacity (IC50) of fraction extracts increased (p < 0.05) with increasing mean particle size (from 17.18 ± 0.59 to 5.29 ± 0.30 mg/mL). Cannabisin B and N-trans-caffeoyltyramine were the most abundant phenolic compounds in the hull fractions (from 267 ± 15.9 to 287 ± 23.1 mg/kg), while cotyledon fractions had higher content of catechin (from 313 ± 12.4 to 744 ± 22.2 mg/kg) and p-hydroxybenzoic acid (from 124 ± 6.47 to 129 ± 8.56 mg/kg (P < 0.05). Well-balanced ω-6 to ω-3 fatty acid ratio (3:1) was determined in all fractions. Antinutrients (trypsin inhibitors, phytic acid, glucosinolates, and condensed tannins) were mostly located in the cotyledon fractions. These findings indicate that the separation of hemp seed meal into different fractions could be used to concentrate valuable target compounds and consequently facilitate their recovery.

The Role of Empirical Rheology in Flour Quality Control

Rheology, as a branch of physics, studies the deformation and flow of matter in response to an applied stress or strain. According to the materials’ behaviour, they can be classified as Newtonian or non-Newtonian (Steffe, 1996; Schramm, 2004). The most of the foodstuffs exhibit properties of non-Newtonian viscoelastic systems (Abang Zaidel et al., 2010). Among them, the dough can be considered as the most unique system from the point of material science. It is viscoelastic system which exhibits shear-thinning and thixotropic behaviour (Weipert, 1990). This behaviour is the consequence of dough complex structure in which starch granules (75-80%) are surrounded by three-dimensional protein (20-25%) network (Bloksma, 1990, as cited in Weipert, 2006). Wheat proteins are consisted of gluten proteins (80-85% of total wheat protein) which comprise of prolamins (in wheat gliadins) and glutelins (in wheat glutenins) and non gluten proteins (15-20% of the total wheat proteins) such as albumins and globulins (Veraverbeke & Delcour, 2002). Gluten complex is a viscoelastic protein responsible for dough structure formation. Among the cereal technologists, rheology is widely recognized as a valuable tool in quality assessment of flour. Hence, in the cereal scientific community, rheological measurements are generally employed throughout the whole processing chain in order to monitor the mechanical properties, molecular structure and composition of the material, to imitate materials’ behaviour during processing and to anticipate the quality of the final product (Dobraszczyk & Morgenstern, 2003). Rheology is particularly important technique in revealing the influence of flour constituents and additives on dough behaviour during breadmaking. There are many test methods available to measure rheological properties, which are commonly divided into empirical (descriptive, imitative) and fundamental (basic) (Scott Blair, 1958 as cited in Weipert, 1990). Although being criticized due to their shortcomings concerning inflexibility in defining the level of deforming force, usage of strong deformation forces, interpretation of results in relative non-SI units, large sample requirements and its impossibility to define rheological parameters such as stress, strain, modulus or viscosity (Weipert, 1990; Dobraszczyk & Morgenstern, 2003), empirical rheological measurements are still indispensable in the cereal quality laboratories. According to the empirical rheological parameters it is possible to determine the optimal flour quality for a particular purpose. The empirical techniques used for dough quality

Gelatinization properties of wheat flour as determined by empirical and fundamental rheometric method

Certain empirical rheological methods are in extensive use in wheat and/or flour research to assess starch gelatinization and pasting behavior primarily due to easy performance and good correlation with final product quality. However, their applications are often associated with specific drawbacks that could be limiting factors for certain applications, such as poor definition of the measured parameters, time-consuming nature, difficulties in interpretation of results, large sample sizes, etc. The listed shortcomings can be overcome by application of fundamental rheological methods that are based on well-defined rheological parameters such as stress, strain, viscosity and modulus. The objective of this study was to optimize the fundamental rheological method for determination of the gelatinization properties of wheat flour that correspondents to the standard widely accepted empirical rheological method—Amylograph method and to compare them in order to determine whether they can be interchangeable depending on different analytical needs. The obtained results have shown that the application of fundamental rheometric procedure for determination of pasting properties of wheat flour provides reliable determination of the gelatinization properties of wheat flour. Moreover, substantial advantages of fundamental rheometric method over the empirical one were identified including smaller sample size, ability to set the desirable heating and shear rate, shorter test duration and better precision.

Content of free amino groups during postharvest wheat and flour maturation in relation to gluten quality

The objective of this study was to monitor the changes in the content of free amino groups during postharvest wheat and flour maturation. The content of free amino groups of wheat flour was analysed immediately after wheat harvest, after 50 days of wheat storage and after 14 days of flour storage varying by wet gluten samples incubation temperatures and incubation times (0, 90 or 135 min at 30°C and after that 180 min at 37°C). The results were observed in relation to wheat-bug damaged kernels content, gluten index values, proteolytic activity and electrophoretic properties of gliadins and glutenins. The content of free amino groups increased during postharvest wheat and flour maturation periods. Proteolytic activity values were the highest 50 days after the wheat storage. The electrophoretic determination indicated a macromolecular redistribution of the gluten proteins from the moment of the wheat harvest until the moment of flour stabilisation.

Changes in the rheological properties of wheat dough during short‐term storage of wheat

BACKGROUND The aim of the present study was to investigate the ability of the small- and large-deformation fundamental rheological tests to monitor the changes during short-term post-harvest storage of wheat. RESULTS At the end of wheat storage period, wet gluten quantity decreased, while gluten index increased in comparison to those of freshly harvested samples. The rheological properties of dough changed over the pre-defined period of storage in terms of becoming more elastic and less extensible in comparison to that of freshly harvested wheat. Visco-elastic properties of weaker flour samples changed more markedly during storage than those of stronger flours, indicating that the intensity of dough rheological changes during wheat storage might be dependent on gluten quality and were the characteristic of wheat variety. CONCLUSION It was shown that small deformation dynamic oscillation and large deformation creep-recovery tests can be successfully employed to monitor the changes in flour quality during wheat storage and that required storage period after wheat harvesting has to be defined according to wheat variety initial rheological properties and its gluten quality.

Predicting rheological behavior and baking quality of wheat flour using a GlutoPeak test

The purpose of this research was to gain an insight into the ability of the GlutoPeak instrument to predict flour functionality for bread making, as well as to determine which of the GlutoPeak parameters show the best potential in predicting dough rheological behavior and baking performance. Obtained results showed that GlutoPeak parameters correlated better with the indices of extensional rheological tests which consider constant dough hydration than with those which were performed at constant dough consistency. The GlutoPeak test showed that it is suitable for discriminating wheat varieties of good quality from those of poor quality, while the most discriminating index was maximum torque (MT). Moreover, MT value of 50 BU and aggregation energy value of 1,300 GPU were set as limits of wheat flour quality. The backward stepwise regression analysis revealed that a high-level prediction of indices which are highly affected by protein content (gluten content, flour water absorption, and dough tenacity) was achieved by using the GlutoPeak indices. Concerning bread quality, a moderate prediction of specific loaf volume and an intense level prediction of breadcrumb textural properties were accomplished by using the GlutoPeak parameters. The presented results indicated that the application of this quick test in wheat transformation chain for the assessment of baking quality would be useful. PRACTICAL APPLICATIONS Baking test is considered as the most reliable method for assessing wheat-baking quality. However, baking test requires trained stuff, time, and large sample amount. These disadvantages have led to a growing demand to develop new rapid tests which would enable prediction of baked product quality with a limited flour size. Therefore, we tested the possibility of using a GlutoPeak tester to predict loaf volume and breadcrumb textural properties. Discrimination of wheat varieties according to quality with a restricted flour amount was also examined. Furthermore, we proposed the limit values of GlutoPeak parameters which would be highly beneficial for millers and bakers when determine suitability of flour for end-use.