Competition for Oxygen Among Oxidative Systems During Bread Dough Mixing: Consequences of Addition of Glucose Oxidase and Lipoxygenase on Yeasted Dough Rheology

The effect on O₂ uptake during the mixing of yeasted dough, either unsupplemented or supplemented with glucose oxidase (GOX), horsebean flour (HB), soybean flour (SB), or combinations thereof, was studied using an airtight mixer. Two wheat flours with a low (flour A) and a high (flour B) content of free polyunsaturated fatty acids were used. Addition of HB or SB provokes a similar increase of O₂ uptake for both wheat flours, whereas addition of GOX causes a larger increase for flour A than for flour B. When the wheat flours were supplemented with HB or SB, addition of GOX caused a small but significant increase of O₂ uptake for flour A. This increase was not observed for flour B. The mixing tolerance of dough A, determined with the Chopin Consistograph, is increased by GOX addition. However, this effect is less pronounced when flour A is supplemented with HB or SB. Similarly, the relaxation index of dough B is decreased by GOX addition, but the decrease is less distinct in the presence of HB or SB. These results can be explained by a competition among yeast, GOX, and lipoxygenases (present in wheat, HB, and SB flours) for the O₂ uptake by dough, which likely decreases the amount of hydrogen peroxide produced by GOX during dough mixing. This competition for O₂ consequently also modifies the rheological properties of dough.     

Glucose Oxidase Effects on Gluten and Water Solubles

Hydrogen peroxide was responsible for the improving the effect of glucose oxidase in breadmaking. The mechanism by which H₂O₂ has its effect is not known. The objective of this study was to determine whether the H₂O₂ produced by glucose oxidase affected the gluten proteins or the water-soluble fraction of flour. Glucose oxidase had no effect on gluten protein as measured by protein solubility or the relative viscosity of soluble protein (solubilized using 1.5% w/v SDS). However, glucose oxidase did affect the water-soluble fraction. The sulfhydryl content of the water-soluble fraction extracted from flour or dough decreased in the presence of glucose oxidase. Glucose oxidase also caused oxidative gelation of the water-soluble fraction extracted from flour. However, the viscosity of the water-soluble fraction extracted from fermented doughs containing glucose oxidase decreased when higher levels of glucose oxidase were used (≥5.0 units of glucose oxidase). Glucose oxidase appeared to have the same oxidizing action independent of whether the water-soluble fraction was boiled or not.     

Metabolite Analysis Allows Insight into the Differences in Functionality of 25 Saccharomyces cerevisiae Strains in Bread Dough Fermentation

During dough fermentation, yeast (Saccharomyces cerevisiae) changes the physical properties of the dough matrix. In this study, we investigate if different yeast strains have an impact on dough rheology and on the gas holding capacity of fermenting dough. Furthermore, we analyze whether observed differences are linked to the metabolite profiles of the yeast strains. More specifically, the impact of 25 yeast strains on dough spread, dough fermentation properties, and dough metabolite profile was analyzed. Our results demonstrate large differences in the fermentation ability and metabolite profile of the 25 strains. Analysis of metabolites in fermented dough confirmed that acetic acid and succinic acid are likely responsible for the lowering of dough pH during fermentation and that the onset of CO₂ release from dough is related to dough pH rather than to the volume of CO₂ within the dough. Our results further suggest that the spread test is an inadequate tool to quantify rheological differences observed for strains with different fermentation profiles.     

Pyranose Oxidase from Trametes multicolor Impacts Dough and Bread Microstructure

Pyranose oxidase (P₂O) improves wheat flour dough stability and bread quality. We related its effect on dough spread behavior to that on dough and bread crumb structure. Increasing P₂O addition levels gradually reduced dough flow. High P₂O addition levels further increased dough strength, significantly increased dough cell wall thickness, and decreased bread loaf volume. Taken together, affecting dough spread behavior impacts dough and bread (crumb) structure, and dough structure largely determines bread crumb structure.     

Effects of Salt,Polyethylene Glycol,and Water Content on Dough Rheology for Two Red Spring Wheat Varieties

In this research, the relationship between dough rheology and water behavior was investigated in response to two osmotic regulators, salt (NaCl) and polyethylene glycol (PEG), using two Canadian Western Red Spring (CWRS) wheat varieties (Harvest and Pembina). The effects of NaCl (0.5, 1.0, and 1.5 g/100 g of flour) and PEG 400 (2.5, 5.0, and 7.5 g/100 g of flour) on dough rheology (oscillatory and creep) were estimated by using a central composite design. Variation of NaCl showed a significant effect on the phase angle δ, indicating that increasing the NaCl resulted in a more elastic dough. The opposite trend was observed with the addition of PEG. PEG 400 exerted a softening effect owing to plasticization, so that a more compliant liquid‐like dough was produced. The effects of water content (±10% of farinograph absorption) and PEG molar mass on dough rheology and freezable water content were estimated by using a full factorial design. PEGs with different molar mass (400, ≈1,600, and 3,350 g/mol) were added at a concentration of 1 g/100 g of flour. The water content significantly affected all dough rheological attributes, whereas PEG molar mass had no effect. The complex shear modulus (G* ) decreased with increasing water content, and dough creep compliance (J _max) increased. The elastic response of dough, determined as the relative elastic part (J _el) decreased with increasing water content. A high correlation was found between the freezable water content and dough rheological attributes.     

Glucose Oxidase in Breadmaking Systems

The mechanism of glucose oxidase action in breadmaking was investigated by studying the baking performance of glucose oxidase, the active ingredient that it produced, and its effect on the rheological properties of dough. Glucose oxidase improved the loaf volume of bread made by 45-, 70-, and 90-min fermentation processes. Although the increase in loaf volume was significant, it was less than that obtained with an optimum level of KBrO₃. With the 90-min fermentation process, the crumb grain of bread was similar for loaves oxidized with optimum levels of glucose oxidase or KBrO₃. The rheological properties of doughs containing glucose oxidase and doughs containing no oxidant were compared. Doughs made with glucose oxidase had higher G′ and G″ and lower tan δ values than doughs made without an oxidant. Hydrogen peroxide was responsible for a drying effect in doughs. This drying effect of glucose oxidase was reduced significantly by incorporation of free radical scavengers into the dough.     

Association of Glutenin Subunit Composition and Dough Rheological Characteristics with Cookie Baking Properties of Soft Wheat Cultivars

The effect of flour type and dough rheology on cookie development during baking was investigated using seven different soft winter wheat cultivars. Electrophoresis was used to determine the hydrolyzing effects of a commercial protease enzyme on gluten protein and to evaluate the relationships between protein composition and baking characteristics. The SDS‐PAGE technique differentiated flour cultivars based on the glutenin subunits pattern. Electrophoresis result showed that the protease degraded the glutenin subunits of flour gluten. Extensional viscosities of cookie dough at all three crosshead speeds were able to discriminate flour cultivar and correlated strongly and negatively to baking performance (P < 0.0001). The cookie doughs exhibited extensional strain hardening behavior and those values significantly correlated to baking characteristics. Of all rheological measurements calculated, dough consistency index exhibited the strongest correlation coefficient with baking parameters. The degradation effects of the protease enzyme resulted in more pronounced improvements on baking characteristics compared with dough rheological properties. Stepwise multiple regression showed that the dough consistency index, the presence or absence of the fourth (44 kDa) subunit in LMW‐GS and the fifth subunit (71 kDa) subunit in HMW‐GS were predominant parameters in predicting cookie baking properties.     

Effects of Oxido-Reductants on Rheological Properties of Wheat Flour Dough and Comparison with Some Characteristics of Extruded Noodles

The effects of oxido-reductants on the rheological properties of wheat flour dough were evaluated by using a capillary rheometer and an oscillatory rheometer at three temperatures. The oxidants potassium iodate (KIO₃) and l -ascorbic acid (l -AA) significantly increased the apparent viscosity and G′ and decreased loss tangent at low temperatures of 30 and 60°C due to enhanced formation of disulfide bonds. The reductant glutathione (GSH) had the opposite effect. Heating caused the gelatinization of starch, which diminished the effects of the oxido-reductants and produced doughs with similar rheological properties at 80°C. The correlation between dough rheology and characteristics of extruded noodles was also studied.     

Modified Dough Preparation for Alveograph Analysis with Limited Flour Sample Size

Dough rheological characteristics obtained by alveograph testing, such as extensibility and resistance to extension, are important traits for determination of wheat and flour quality. A challenging issue that faces wheat breeding programs and some wheat research projects is the relatively large flour sample size of 250 g required for the standard alveograph method (AACCI Approved Method 54‐30.02). A modified dough preparation procedure for a small flour sample size was developed for the alveograph test method. A dough was prepared by mixing 80 g of flour with 60% water absorption (2.5% salt solution) for 4 min in a 100 g pin mixer; it was then sheeted and cut into three patties of defined thickness. Data generated by the modified dough preparation method were significantly correlated with the results from the approved alveograph method. The correlation coefficients (r) for each of six alveograph dough characteristics of 40 different advanced breeding lines and wheat varieties were 0.92 for P (mm H₂O), 0.73 for L (mm), 0.83 for W (10^–4 J), 0.90 for P/L, 0.90 for le (%), and 0.76 for G. The modified dough preparation was easier and more convenient than the approved method, and test time for the modified dough preparation was shorter by 20–25 min. This modified dough preparation procedure for the alveograph may be useful for wheat breeding programs as well as an alternative to the approved alveograph method for milling and baking industries and wheat quality research.     

The Combination of Rhizopus chinensis Lipase and Transglutaminase Affects the Rheology and Glutenin Macropolymer Properties of Frozen Dough

The combination of Rhizopus chinensis lipase (RCL) and transglutaminase (TG) was previously reported to improve the quality of frozen dough bread. In this study, the effects of RCL, TG, and their combination on the modification of glutenin macropolymer (GMP) and rheological properties of dough during frozen storage were investigated. Frozen storage changed both GMP and rheology properties of dough. TG treatment significantly decreased the ratio of high‐molecular‐weight glutenin subunits to low‐molecular‐weight glutenin subunits and GMP content in fresh dough, and GMP particle size increased. The effect of RCL on GMP properties was not significant, but its combination with TG dramatically increased the proportion of the larger particles and weighted average volume (D_4.3) in GMP. The treatment with the enzyme combination could have inhibited the depolymerization of GMP, which slowed down the decrease rate of some parameters such as GMP content, proportion of larger particles, D_4.3, and release of free amino and thiol groups during frozen storage. The modification of GMP properties by enzyme treatment weakened the effect of the freezing process on rheological properties of dough, especially TG treatment and its combination with RCL. Correlation between GMP particle size and dough properties (dough tensile force and elastic modulus) after freezing and enzyme treatment were confirmed.     

Comparison of Small and Large Deformation Measurements of Whole Meal Rye Doughs

The rheological properties of rye flour-water-salt doughs prepared from different flour types (different falling number and coarseness) at different water levels were studied after mixing and after 90 min of incubation (30°C and 80% rh). Both the effect of water and the coarseness of the flour had significant effects on storage modulus (G′) measured by oscillatory test in the linear viscoelastic region and on compressional force measured at large deformation. The results of the two rheological methods correlated very well with each other (correlation coefficients varied in the different doughs at r = 0.975–0.999). Dough rheological measurements suggested that falling number did not have a statistically significant effect on dough rheology after mixing or incubation. Although the two rheological methods correlated well, the responses for incubation were different. In the small deformation method, the storage modulus of all doughs, independent of the falling number, decreased during incubation, whereas in the large deformation method, only the hardness of doughs made from flours with lower falling number decreased during incubation. The rheological measurements of doughs after mixing and the viscosity measurements of flourwater suspension at 30 and 40°C did not correlate with each other. Total pentosans have great effect on viscosity measurements of flour-water suspensions, whereas flour particle size and soluble pentosans correlated more with rheological properties of doughs (r = 0.851 between G′ and soluble pentosans).     

Evaluation of a New Viscometer Performance in Predicting the Technological Quality of Soft Wheat Flour

Gluten aggregation properties were investigated by means of the GlutoPeak device, a viscometer recently proposed as a rapid and sensitive test for measurement of wheat flour technological performance. In this study, 62 soft wheat flour samples of different quality and end use were utilized to evaluate if the GlutoPeak parameters could adequately predict chemical and rheological characteristics of soft wheat flour dough, that is, protein content measured by the Kjeldahl method, dough strength measured by a Chopin alveograph, and dough stability and water absorption measured by a Brabender farinograph. Linear correlation analysis showed that most GlutoPeak curve parameters were strongly correlated with protein content, dough strength, and water absorption. The statistical models, obtained by a stepwise multiple regression method, showed the GlutoPeak device to be a promising tool to characterize wheat flour (R_adj² = 0.84 for protein content, R_adj² = 0.71 for dough strength, and R_adj² = 0.67 for water absorption). The rather high accuracy of the prediction models for the three mentioned parameters confirmed that GlutoPeak parameters are well correlated with other frequently used flour quality parameters and are able to describe flour technological performance.     

Addition of Glucose Oxidase for the Improvement of Refrigerated Dough Quality

Refrigerated dough encompasses a wide range of products and is a popular choice for consumers. Two of the largest problems that occur during refrigerated dough storage are dough syruping and loss of dough strength. The goal of this study was to evaluate glucose oxidase as an additive to refrigerated dough with the purpose of maintaining dough strength and retarding dough syruping. Refrigerated dough was evaluated for the degree of dough syruping (DDS), dough strength, rheological characteristics, baking quality, and protein quality. The addition of glucose oxidase at 10 mg/kg was able to significantly (P < 0.05) reduce dough syruping and maintain the strength of the dough. Addition of glucose oxidase at 5 and 25 mg/kg was not able to reduce the level of dough syruping at a satisfactory level. Degradation of protein was found to occur during storage of refrigerated dough. DDS had a negative correlation (r = –0.60 to –0.94) to the level of polymeric proteins and a positive correlation (r = 0.60 to 0.98) to the low‐molecular‐weight proteins. Overall, glucose oxidase at 10 mg/kg can improve refrigerated dough quality by reducing dough syruping and maintaining dough strength.     

Rheological Properties of Soft Wheat Flour Doughs: Effect of Salt and Triglycerides

The small deformation rheological properties of wheat flour doughs in relation to their structure and hydration were studied by dynamic mechanical thermal analysis, differential scanning calorimetry, and electron spin resonance. The effect of salt and triglycerides was also examined and compared with results we obtained previously on starch dispersions. Moisture content was adjusted to 48 or 60% (w/w, wb). Samples contained 0–16% NaCl (g/100 g of flour‐water) and 0–18% triolein or lard (g/100 g of flour‐water). The obtained results suggested that starch has an active role in determining the evolution of dough rheological characteristics during heating. The main factors controlling rheological behavior during thermal treatment are the volume fraction and deformability of starch granules. Gluten changes the viscoelasticity of the continuous phase and competes with starch for water. The addition of sodium chloride to flour dispersions shifted the structural disorganization and rigidity increased during heating to higher temperatures. At >7% NaCl, the reverse effect was observed. The mechanism controlling the effect of salt on dough rheological behavior was explained in terms of effect on water properties and on starch structure and hydration. Triglycerides had a lubricant effect (i.e., lowering G′ modulus) on the wheat flour dough system. These effects are of great importance for production and quality of bakery products.     

Effect of Damaged Starch and NaCl Level on the Dough Handling Properties of a Canadian Western Red Spring Wheat

The effects of damaged starch and NaCl (1 and 2% w/w [flour weight]) on the dough handling properties of a wheat flour (Triticum asetivum L. ‘Roblin’) were investigated with rheological and textural methods. Damaged starch levels of the base flour and three remilled flours (using reduction rolls with decreasing gap sizes) were 5.42, 6.23, 7.30, and 8.43%. Rheological measurements on the dough showed that the complex modulus increased and the loss tangent (tan δ) decreased with increasing damaged starch levels in the flour, indicating that greater amounts of damaged starch produced stiffer dough. The base flour produced doughs with the highest creep compliance value (J _max), whereas the flour with the most damaged starch deformed the least. Higher levels of salt produced stiffer dough that deformed less, as evident by the higher complex modulus and lower creep compliance, compared with 1% NaCl. Damaged starch overall decreased dough stickiness (N), work of adhesion (N·s), and cohesiveness (mm). Increasing the salt content decreased the stickiness of the doughs. Increasing the damaged starch greatly increased dough extensibility at 1% NaCl. The greater amounts of damaged starch in the remilled flour mitigated some of the negative effects of reducing the salt content on the dough machinability.     

Impact of Bran Addition on Water Properties and Gluten Secondary Structure in Wheat Flour Doughs Studied by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy

The aim of this work was to elucidate the underlying physical mechanism(s) by which bran influences whole grain dough properties by monitoring the state of water and gluten secondary structure in wheat flour and bran doughs containing 35–50% moisture and 0–10% added bran. The system was studied with attenuated total reflectance (ATR) FTIR spectroscopy. Comparison of the OH stretch band of water in flour dough with that in H₂O‐D₂O mixtures having the same water content revealed the formation of two distinct water populations in flour dough corresponding to IR absorption frequencies at 3,600 and 3,200 cm^–1. The band intensity at 3,200 cm^–1, which is related to water bound to the dough matrix, decreased and shifted to lower frequencies with increasing moisture content of the dough. Addition of bran to the dough caused redistribution of water in the flour and bran dough system, as evidenced by shifts in OH stretch frequency in the 3,200 cm^–1 region to higher frequencies and a reduction in monomeric water (free water). This water redistribution affected the secondary structure of gluten in the dough, as evidenced by changes in the second‐derivative ATR‐FTIR difference spectra in the amide I region. Bran addition caused an increase in β‐sheet content and a decrease in β‐turn (β‐spiral) content. However, this bran‐induced transconformational change in gluten was more significant in the 2137 flour dough than in Overley flour dough. This study revealed that when bran is added to flour dough, water redistribution among dough components promotes partial dehydration of gluten and collapse of β‐spirals into β‐sheet structures. This transconformational change may be the physical basis for the poor quality of bread containing added bran.     

Comparison of Small and Large Deformation Rheological Properties of Wheat Dough and Gluten

The rheological properties of dough and gluten are important for end‐use quality of flour but there is a lack of knowledge of the relationships between fundamental and empirical tests and how they relate to flour composition and gluten quality. Dough and gluten from six breadmaking wheat qualities were subjected to a range of rheological tests. Fundamental (small‐deformation) rheological characterizations (dynamic oscillatory shear and creep recovery) were performed on gluten to avoid the nonlinear influence of the starch component, whereas large deformation tests were conducted on both dough and gluten. A number of variables from the various curves were considered and subjected to a principal component analysis (PCA) to get an overview of relationships between the various variables. The first component represented variability in protein quality, associated with elasticity and tenacity in large deformation (large positive loadings for resistance to extension and initial slope of dough and gluten extension curves recorded by the SMS/Kieffer dough and gluten extensibility rig, and the tenacity and strain hardening index of dough measured by the Dobraszczyk/Roberts dough inflation system), the elastic character of the hydrated gluten proteins (large positive loading for elastic modulus [G′], large negative loadings for tan δ and steady state compliance [J_e⁰]), the presence of high molecular weight glutenin subunits (HMW‐GS) 5+10 vs. 2+12, and a size distribution of glutenin polymers shifted toward the high‐end range. The second principal component was associated with flour protein content. Certain rheological data were influenced by protein content in addition to protein quality (area under dough extension curves and dough inflation curves [W]). The approach made it possible to bridge the gap between fundamental rheological properties, empirical measurements of physical properties, protein composition, and size distribution. The interpretation of this study gave indications of the molecular basis for differences in breadmaking performance.     

Effect of l-Ascorbic Acid on the Rheological Properties of Wheat Flour-Water Dough

L-Ascorbic acid (AsA) and its related compounds play an important role as improvers in bread production. Addition of AsA and its related compounds, such as dehydro-L-AsA (DHA) and 2,3-diketo-L-gulonic acid (DKG), affected the rheological properties of flour-water dough during mixing, especially hardness. Addition of 10 or 100 ppm AsA increased the dough hardness of samples as compared with the control dough. Addition of DHA or DKG to dough only slightly increased hardness. Addition of p-quinone significantly increased the hardness. Both glutathione (GSH) and its oxidized form (GSSG) drastically decreased the hardness. Contents of AsA in the treated dough decreased and contents of DHA increased during mixing, suggesting that oxidation occurred. The oxidation rate of AsA was influenced by the concentration of AsA added. The improving effect of AsA on the rheological properties of flour-water dough seemed to be mostly dependent on reactive intermediate oxidation products such as O₂^-, while the contribution of DHA was rather limited.     

Dinoseb as a specific inhibitor of nitrogen fixation in soil

N₂ fixation, estimated by reduction of C₂H₂, by a loamy soil amended with glucose was highly sensitive to the pesticide, 4,6-dinitro-o-sec-butylphenol (DNBP).At a concentration of 6 parts/10⁶ DNBP inhibited reduction of C₂H₂ by 90% in an anaerobic artificial soil system. Studies of the nitrogen-fixing enzyme system isolated from Azotobacter suggested that DNBP may compete with ATP for the same site on the enzyme.     

Improvement of Sorghum-Wheat Composite Dough Rheological Properties and Breadmaking Quality Through Zein Addition

Addition of sorghum flour to wheat flour produces marked negative effects on rheological properties of dough and loaf volume. Although there are notable differences in the chemical composition of sorghum proteins (kafirins) compared with wheat gluten that might imply poor functionality in breadmaking systems, a larger constraint may be the unavailability of kafirins due to encapsulation in protein bodies. In this study, zein, the analogous maize prolamin to kafirin, was used to determine the potential effects of protein-body-free prolamins on dough rheology and baking quality of wheat-sorghum composite flour. Mixograms run at 35°C (above the glass transition temperature of zein) were significantly (P < 0.01) improved with addition of zein. Mixogram peak heights increased while mixing time decreased uniformly with addition of zein. Dough extensibility studies showed an increase in maximum tensile stress, while baking studies showed an increase in loaf volume with increasing amounts of added zein. These data are supported by a previous study showing that, in a model system, zein mixed with starch can form viscoelastic networks, and suggest that kafirin, if made available, could contribute to dough formation.