Dough Mixing Research Articles

GLUTEN PRODUCTION : Analysed In Terms Of Volume Expansion, Extensibility And Rheological Characterisation

Gluten is the protein in flour that gives the viscoelastic properties of dough. There are still inadequate understandings of the knowledge concerning gluten during the dough mixing and the unique properties that gluten posses. Gluten production was examined in terms of quantity and quality of gluten. Quantity of gluten was measured in terms of wet and dry gluten content. Wet gluten content was determined by weighing the gluten obtained from the dough washed under running tap water. The wet gluten was dried using air oven drying method to obtain dry gluten content. In terms of quality, the gluten was analysed in terms of volume expansion, extensibility and rheological characterisation. The volume expansionanalysis was performed by frying the wet gluten in hot oil at 170oC in deep fryer for15 minutes. The volume of fried gluten was measured using mustard seed displacement method and the difference between the volume of fried gluten and the volume of wet gluten is measured as volume expansion of gluten.Key word : Gluten, rheological, wheat

Phytate negatively influences wheat dough and bread characteristics by interfering with cross-linking of glutenin molecules

The influence of added phytate on dough properties and bread baking quality was studied to determine the role of phytate in the impaired functional properties of whole grain wheat flour for baking bread. Phytate addition to refined flour at a 1% level substantially increased mixograph mixing time, generally increased mixograph water absorption, and reduced the SDS-unextractable protein content of dough before and after fermentation as well as the loaf volume of bread. The added phytate also shifted unextractable glutenins toward a lower molecular weight form and increased the iron-chelating activity of dough. It appears that phytate negatively affects gluten development and loaf volume by chelating iron and/or binding glutenins, and consequently interfering with the oxidative cross-linking of glutenin molecules during dough mixing. Phytate could be at least partially responsible for the weak gluten network and decreased loaf volume of whole wheat flour bread as compared to refined flour bread.

Research into the impact of enzyme preparations on the processes of grain dough fermentation and bread quality

The important issue of improvement in the technology of grain bread is the development of measures to improve the rheological properties of dough and bread. With this aim we proposed the use of cellulases, hemicellulases ans oxidoreductases at the stage of dough mixing. It is shown that the application of the studied enzymes for grain emmer and wheat dough contributes to the intensification of non-starch polysaccharides hydrolysis, namely reduction of the content of cellulose by 11 %, hemicelluloses – by 14.3 and 13.0 %, and increase in the content of water-soluble fraction of hemicelluloses.Additionally, the presence of enzyme preparations in the grain dough promotes slowing down of the processes of gluten proteolysis and improvement of its rheological properties that predetermines increase of gas-retaining capacity of the studied system. It was discovered that adding the studied enzyme preparations to grain dough contributes to the intensification of acid and gas generation in it. The resulting effect of biochemical and microbiological changes in grain dough under the influence of enzyme preparations of cellulase, xylanase and glucose oxidase is the improvement in the quality of grain bread compared to the samples without their addition.

Effects of Hofmeister salt series on gluten network formation: Part II. Anion series

Different anion salts from the Hofmeister series were used to investigate their effects on gluten network formation. The effects of these anion salts on the mixing properties of the dough and the rheological and chemical properties of gluten samples extracted from the dough with these respective salts were compared. The aim of this work was to determine how different anion salts influence the formation of the gluten structure during dough mixing. It was found that the Hofmeister anion salts affected the gluten network formation by interacting directly with specific amino acid residues that resulted in changes in gluten protein composition, specifically the percentage of the unextractable polymeric protein fractions (%UPP). These changes consequently led to remarkable differences in the mixing profiles and microstructural features of the dough, small deformation rheological properties of the gluten and a strain hardening behaviour of both dough and gluten samples.

Effects of Hofmeister salt series on gluten network formation: Part I. Cation series

Different cationic salts were used to investigate the effects of the Hofmeister salt series on gluten network formation. The effects of cationic salts on wheat flour dough mixing properties, the rheological and the chemical properties of the gluten extracted from the dough with different respective salts, were investigated. The specific influence of different cationic salts on the gluten structure formation during dough mixing, compared to the sodium ion, were determined. The effects of different cations on dough and gluten of different flours mostly followed the Hofmeister series (NH4+, K+, Na+, Mg2+ and Ca2+). The impacts of cations on gluten structure and dough rheology at levels tested were relatively small. Therefore, the replacement of sodium from a technological standpoint is possible, particularly by monovalent cations such as NH4+, or K+. However the levels of replacement need to take into account sensory attributes of the cationic salts.

Influence of Vacuum Mixing on Structural Characteristics and Physical Properties of Noodle Dough

The effects of vacuum mixing on the structural characteristics and physical properties of noodle dough were investigated using three leading Chinese wheat cultivars. Texture profile analysis showed that vacuum mixed doughs when sheeted all gave significantly higher levels of adhesiveness, elasticity, and chewiness than doughs from nonvacuum mixing. The cross section of sheeted dough mixed at 0.06 MPa had a more continuous and compact microstructure with fewer holes and gaps, as well as more even protein distribution at the surface, as evidenced by scanning electron microscopy and Fourier transform infrared microimaging. However, a higher degree of vacuum was detrimental to the developed network for weak dough. Dough mixed at 0.06 MPa had higher glutenin macropolymer content and lower free thiol group concentration compared with nonvacuum mixed doughs, which may largely relate to the improvement of dough texture. The development of the gluten network for weak gluten flour was more sensitive to the degree of vacuum.

A new standard water absorption criteria based on solvent retention capacity (SRC) to determine dough mixing properties, viscoelasticity, and bread-making quality

Water is necessary for the development of gluten viscoelastic properties and plays an important role in all types of chemical reactions that occur during mixing and baking. Therefore, understanding the nature of all chemical constituents and paying attention to their effects in determining water absorption is crucial for reliable evaluation of the flour bread-making properties and its bread-making performance. In this study, a new standard water absorption criteria (UNIFABS) for Mixograph, Alveograph and bread-making was developed based on the solvent retention capacity of four different solvents: water, lactic acid, sodium carbonate and sucrose. The UNIFABS was developed in order to have a common water absorption criteria for the three methods that satisfies the water absorption capacity as influenced concomitantly by proteins and polysaccharides. The UNIFABS improves the assessment of dough mixing and viscoelastic parameters, and the value of both, Mixograph and Alveograph, in predicting and selecting for bread-making quality in breeding programs.

Effect of Whole Grain Wheat Flour on the Mixing Properties, Oil Uptake, and In Vitro Starch Digestibility of Instant Fried Noodles

The effects of whole grain wheat (WGW) flour on the quality attributes of instant fried noodles were characterized in terms of mixing and oil‐resisting properties as well as in vitro starch digestibility. Higher water absorption and shorter kneading time were required to obtain the optimally mixed dough from WGW flour, and the presence of nonstarch components in the WGW flour lowered the thermal conductivity of the noodles. The use of WGW flour produced instant fried noodles with oil uptake reduced by 30%, which could be correlated with the less porous structure confirmed by the surface and cross‐sectional scanning electron microscope images. When the instant fried noodles were subjected to in vitro starch digestion, the use of WGW flour was effective in suppressing the hydrolysis of starch in the noodles, and the predicted glycemic index of the WGW noodles (80.6) was significantly lower than that of the white wheat noodles (83.3).

Image analysis of dough development: Impact of mixing parameters and wheat cultivar on the gluten phase distribution

Dough mixing is a key step in the wheat gluten-starch separation process promoting gluten agglomeration. The impact of the water/flour ratio (W/F), mixing speed (N), and wheat cultivar (Orvantis, Caphorn, Isengrain) on the protein phase distribution during mixing was studied by macroscopic image analysis. During dough mixing gluten agglomerates grew steadily and finally turned into a filamentous network at optimal dough development (tpeak). Prior to tpeak, neither W/F nor N impacted the average gluten lump diameter at a fixed stage of mixing. For Orvantis significantly larger gluten agglomerates (up to 272 μM) were observed as compared to Caphorn and Isengrain (up to 222 and 144 μM, respectively). Wheat flour cultivar was shown to have an important impact on gluten lump diameter, while mixing parameters (N and W/F) have no direct effect. Mixing parameters merely modulate the absolute gluten lump growth rate, just as they impact the optimal dough development time.

Changes in Semolina Yellow Pigment Content and Carotenoid Composition During Pasta Processing

Changes in total yellow pigment (TYP) content and carotenoid composition were examined at different stages of pasta processing. Semolina samples were milled from durum genotypes with and without the Lpx‐B1.1 gene deletion and then processed into dry pasta. Significant pigment loss (12.8–15.3%) based on TYP content was observed from semolina to dough in genotypes without the gene deletion. Such loss remained low (2.0–2.8%) for genotypes with the Lpx‐B1.1 gene deletion. Extrusion and drying processes did not result in substantial pigment loss. The overall pigment loss (from semolina to dried pasta) of genotypes with the gene deletion was 9.1–12.8%, in comparison with 19.0–21.7% in genotypes without the deletion. Changes in carotenoids examined by ultra‐performance liquid chromatography showed that lutein decreased gradually from representing 80% of total carotenoids to 70% of total carotenoids during pasta processing. The reduction of lutein was mostly during dough mixing, with a decrease of 16.7% in genotypes with the Lpx‐B1.1 deletion and 27.8% in genotypes without the deletion. Minor carotenoids increased during pasta drying, possibly at the expense of lutein. Results of this study showed that although breeding for elevated yellow pigments is the key, pasta color can be further improved by reducing pigment losses at different stages of pasta processing through selection of genotypes with Lpx‐B1.1 deletion and applying a vacuum during mixing and extrusion processes.

Structural characterization of proteins in wheat flour doughs enriched with intermediate wheatgrass (Thinopyrum intermedium) flour

The high protein and fiber content of intermediate wheatgrass (IWG) – together with its interesting agronomic traits and environment-related benefits – make this perennial crop attractive also for human consumption. Structural characteristics of the proteins in IWG/hard wheat flour (HWF) doughs (at IWG:HWF ratios of 0:100, 50:50, 75:25 and 100:0) – including aggregate formation, thiols availability, and secondary structure changes during dough mixing – were investigated. Proteins in IWG-doughs had higher solubility and thiol content – as function of IWG content – suggesting that protein network was mostly based on non-covalent interactions. While 50% IWG-enrichment gave an increase in random structures, enrichment at ⩾75% resulted in a decrease in β-sheets with an increase in random structures, indicating a decrease in structural order. The observed differences in protein molecular configuration and interactions in HWF compared to IWG doughs necessitate further investigation to establish their impact on the quality of IWG-enriched bread.

Effect of Mixing Time and Speed on Experimental Baking and Dough Testing with a 200 g Pin Mixer

Undermixing or overmixing the dough results in varied experimental loaf volumes. Bread preparation requires a trained baker to evaluate dough development and determine the stop points of the mixer. Instrumentation and electronic control of the dough mixer would allow for automatic mixing. This study used a 200 g mixer that provided an output signal during dough mixing to evaluate potential mixing stop points. The effect of varied mixing time on the baked loaf volume was tested by using three flours with protein contents of 10.6, 12.4, and 13.8%. Dough samples were undermixed, mixed to peak, and overmixed. Overmixing by 0.6 min reduced the loaf volume in all flours tested, by 16–50 cm3 at 90 rpm and by 29–68 cm3 at 118 rpm. When the high‐protein flour sample was undermixed, the largest baked loaves were produced, with an average volume of 922 cm3. A second objective studied the similarities and differences between a 200 g mixer and a 35 g mixograph. The same flours were mixed on both units. The mixing peaks for the 200 g mixer were normalized with the 35 g mixograph peaks. When flour and water were used, the mixing times for the 200 g mixer averaged 0.7, 1.2, and 1.6 min shorter than the 35 g mixograph, at 90, 104, and 118 rpm, respectively. Although both the 200 g mixer and the 35 g mixograph system look mechanically similar, they both have unique mechanical motion, speeds, and sample sizes. Their results may show similar trends, but their measured values are usually different. However, when other baking ingredients were included in the 200 g mixer at 90 rpm, the mixing times were within 0.2 min of the 35 g mixograph times for three of four flours.

Arabinoxylan content and characterisation throughout the bread‐baking process

SummaryEnd‐use quality of wheat (Triticum aestivum L.) is influenced in a variety of ways by nonstarch polysaccharides, especially arabinoxylan (AX). The objective of this study was to track total and water‐extractable AX (TAX and WEAX, respectively) throughout the bread‐baking process, using wholemeal and refined flour. The TAX and WEAX content and the ratio of arabinose: xylose were assessed in flour, mixed dough, proofed dough and the bread loaf, which was separated into crumb, upper crust and bottom crust. Changes in TAX during the baking process differed between the refined flour and wholemeal samples, suggesting a change in the TAX availability which we ascribe to molecular interactions and heat treatment. WEAX content dramatically decreased during baking, suggesting that oxidative cross‐linkages rendered it unextractable. Higher levels of WEAX and lower levels of arabinose substitution were correlated with higher loaf volumes for refined flour among the hard wheat varieties. Having a better understanding of the importance of both WEAX content and arabinose substitution allows for directed breeding efforts towards improved hard wheat varieties for optimum bread baking.

Effect of mixing time on the structural characteristics of noodle dough under vacuum

The structural characteristics of noodle dough under different vacuum mixing times were investigated using three flour samples by texture profile analysis (TPA), SEM, FTIR micro-imaging, and by measuring the glutenin macropolymer and free –SH content. The sheeted dough mixed for 8min presented better textural properties and a more compact and even microstructure. Insufficient mixing resulted in an uneven distribution and an inadequately developed gluten network, especially for weak-gluten flour (Jimai 22). Excessive mixing was detrimental to the developed dough network and decreased the uniformity of component spatial distribution. Furthermore, excessive mixing led to a decrease in GMP content as well as the increase in free –SH content. Flours with different protein characteristics behaved differently. The TPA, microstructure and free –SH content of dough of Zhengmai 366 was less affected by mixing time than that of Jimai 22, suggesting that strong-gluten flour has better noodle dough mixing tolerance.

The influence ofFusariuminfection on wheat (Triticum aestivumL.) proteins distribution and baking quality

Under artificial Fusarium infection the total glutenin content determined by chromatographic (RP-HPLC) method was significantly reduced in comparison to gliadins which were increased. Among protein types, α-GLI and HMW-GS were the highest affected. Artificial Fusarium infection significantly increased GLI/GLU ratio when compared with the natural infected samples. Artificial Fusarium infection dramatically decreased the dough mixing tolerance and had a considerable negative effect on dough energy, maximum resistance, and resistance/extensibility ratio. Disturbed GLI/GLU ratio and an increased amount of mycotoxin DON under artificial Fusarium infection showed a strong negative impact on affected functional properties of dough and bread. Total and γ-GLI as well as GLI/GLU ratio were significantly positively affected by mycotoxin DON in contrast to total GLU, HMW-GS and LMW-GS which were negatively affected. Results indicated that the stability of baking quality parameters of cultivars more tolerance to the Fusarium infection can be well define by lower accumulation of mycotoxin DON.

Interaction of Sorghum Tannins with Wheat Proteins and Effect on in Vitro Starch and Protein Digestibility in a Baked Product Matrix.

Carbohydrates contribute the most dietary calories, which makes starchy foods a logical target for modifying calorie intake. This study investigated the interaction of sorghum bran proanthocyanidins (PA) with proteins during wheat flour tortilla processing and impact on in vitro starch digestibility. Brans from wheat, white (low in phenols), brown (high PA), and black (high monomeric flavonoids) sorghum were used. Changes in phenolic profile, starch, and proteins were evaluated. Dough mixing drastically decreased extractable PA (61-72%) but not monomeric phenolics; higher MW PA decreased the most. The high PA bran dough produced the highest insoluble proteins (460 vs 330 mg/g protein for other sorghum brans) at 25% baker's substitution. The high PA bran tortillas also had higher slow digesting starch and lower rapidly digesting starch than all other bran treatments. Significant sorghum PA-gluten interactions occur during dough mixing that may slow starch digestibility in the baked products.

Genetics of End‐Use Quality Differences between a Modern and Historical Spring Wheat

ABSTRACTThe goal of this project was to determine the genetic basis for quality differences between a modern semidwarf spring wheat (Triticum aestivum L.) cultivar McNeal and a historically important standard height cultivar Thatcher. McNeal is higher yielding with lower grain protein than Thatcher, yet has stronger gluten properties important in bread making. Grain from a total of 160 recombinant inbred lines including 80 semidwarf and 80 standard‐height lines grown in three environments was tested for bread‐making quality. A genetic map of 609 markers was used to identify bread‐making quality quantitative trait loci (QTL) influencing flour protein, dough mixing, and baking properties. The McNeal allele for semidwarf habit at Rht‐D1 had the largest impact on end‐use quality parameters, including flour protein and loaf volume. The primarily negative impact of this allele on quality in McNeal was mitigated by alleles for increased dough strength at other QTL. The allele with the greatest effect on strength was at Gli‐B1. Other alleles for increased end‐use quality, especially alleles impacting flour protein, tended to be negatively associated with previously identified alleles for grain yield and its components. In sum, this paper shows that the introduction of the Rht alleles for semidwarf habit have presented a challenge to the maintenance of superior end‐use quality in modern hard red spring wheat cultivars.

Predicting the quality of wheat flour dough at mixing using an expert system

Modelling the links between the mixing process conditions of wheat flour dough and the properties of the dough is a challenge. This paper presents a systematic modelling approach based on qualitative algebra to represent human expertise in this domain. Qualitative models of wheat dough mixing have been implemented as an expert system, called Ascopain. The relations between the process conditions – flour specifications and kneading conditions – and the dough sensory properties, have been formalised by means of qualitative functions. An extensive evaluation of Ascopain is provided by comparing the simulation results, first to experts' predictions, and second, to experimental results of sensory evaluation of mixed dough properties. The good matching level proves the accuracy and the robustness of the expert-system and, overall, its ability to implement a reasoning on the influences of process conditions to predict actual dough properties, starting from ingredient characteristics.

Flour quality and disproportionation of bubbles in bread doughs

The bread making process transforms wheat flour doughs into highly porous breads. Bread has been shown (Wang, Austin and Bell, 2011) to be a single, open cell that is massively interconnected giving it a maze-like structure that encompasses the entire volume. The solid strands are also porous and contain closed cells. How the bubbles in dough mix partition into these open and closed cells in bread is not known. This study was undertaken to track changes in bubbles in doughs using 3-D X-ray microtomography techniques as doughs proofed and were baked. The mechanical properties of doughs were measured to establish how dough rheology impacted bubble growth. The doughs were made with ‘medium strong’ Canadian flour (CWRS) and ‘weak’ Australian flours (Wylk). Both doughs had similar protein amounts and strain-hardening characteristics; however the CWRS dough was more elastic. The scans identified formation of clusters of partially-coalesced bubbles from which one cluster grew to form a massively interconnected, single, closed cell in doughs as doughs proofed. Microscopy studies confirmed that the open cell in breads was made of partially-coalesced bubbles. Compared to the dough made with the Australian flours, the dough made from Canadian flour had a thicker dough layer separating bubbles, smaller size bubbles and a slower rate of formation of the continuous structure. This study highlights the critical role of dough elasticity and the disproportionation phenomena of bubble growth in controlling the quality of cell structures in dough and baked products.

The effects of bread‐making process factors on Australian sweet lupin‐wheat bread quality characteristics

SummaryFactorial experimental design was used to investigate the effects of: sponge proofing time (min), sponge and dough mixing time (min), final proofing time (min), final proofing temperature (°C) and baking time (min) on Australian sweet lupin‐wheat bread physical attributes. Factorial models show that bread specific volume was positively associated with sponge and dough mixing time (P = 0.01) and baking time (P = 0.02). Crumb area was positively associated (P = 0.01) with sponge and dough mixing time. Final proofing time positively influenced cell wall thickness (P < 0.01) and cell diameter (P < 0.01) but negatively affected number of cells (P < 0.01). Cell diameter was positively associated with baking time (P = 0.04), whilst number of cells was negatively influenced by sponge and dough mixing time (P = 0.01). Instrumental springiness was positively associated with sponge and dough mixing time (P = 0.02). Sponge and dough mixing and baking times were the two most significant process parameters affecting the bread physical quality and hence should be optimised.