Effect of Amaranthus and Buckwheat Proteins on Wheat Dough Properties and Noodle Quality

Isoelectric protein concentrates (IPC) were prepared from one buckwheat (Fagopyrum esculentum) and five Amaranthus genotypes. Their effect on the mixing properties of a wheat flour was studied. Mixograph and dynamic oscillatory measurements showed significant increases in dough strength with the addition of 2 and 4% IPC, correlated to the water-insoluble fraction level of the IPC. The same IPCs were used at 2% level to supplement a wheat flour in making Chinese dry noodles. Measurable changes in both the raw and cooked noodle color were observed, and the change caused by addition of buckwheat IPC was substantial. Some of the IPCs caused an increase in cooking loss and only one caused an increase in weight, while increase in volume of the cooked noodles was not significantly affected. The changes in the rheological properties of cooked noodles due to addition of IPCs were measured. Overall, their effects were favorable, but the changes were statistically significant in only a few cases. The substantial dough-strengthening effect of the IPCs was hence not effectively translated into improved cooked noodle quality, and possible reasons for this are discussed.     

Biaxial Extensional Viscosity of Sheeted Noodle Dough

The flows encountered during the sheeting process contain a more extensional component and more stretching than simple shear. Evaluating the properties of the extensional rheological flow of wheat flour dough is essential to better understand the sheeting process and the final quality of the product. Our results show that the curves of biaxial extensional viscosity versus extensional strain rate for dough from different wheat cultivars including Dark Northern Spring (DNS), Hard Red Winter (HRW), and Western White Wheat (WW) with protein contents of 7.81–18.09% and water contents of 32–40% could be discriminated. During a lubricated compression test, the sheeted dough displayed a region of extensional thickening followed by a region of mild extensional thinning, giving rise to an s-shaped extensional stress-strain rate curve. The higher degree of extensional thinning was exhibited for the sheeted dough prepared from the flour of DNS and HRW wheat mixture with an extensional thinning index of n = 0.65–0.74; while the lower degree of extensional thinning was displayed for the DNS wheat with an extensional thinning index of n = 0.89–0.96. The data of biaxial extensional viscosity (η_Bmax) versus water content and protein content could be described by power relationships. The results suggest that biaxial extensional viscosity can be a useful modeling and process design parameter that objectively represents the rheological properties during dough sheeting.     

Influence of Bioprocessed Wheat Bran on the Physical and Chemical Properties of Dough and on Wheat Bread Texture

The aim of this work was to assess the influence of wheat bran addition on the rheological properties of dough and on subsequent wheat bread volume and texture. Two types of bioprocessed bran (fermentation with yeast or with yeast plus enzymes) were studied in breadmaking at a substitution level of 20% (sufficient to deliver 6 g of dietary fiber per 100 g of product, the minimum for the European Food Safety Authority high‐fiber nutrition claim). Fermentation activated endogenous enzymes of bran, which together with exogenous enzymes modified the state of fiber in bran, resulting in solubilization of arabinoxylans and slight degradation of the insoluble fiber. Fermentation and enzyme treatment of bran compensated for the increased hardness (+100%) and the volume‐decreasing (–21%) effect observed with untreated bran. Analysis with partial least squares regression suggested the efficacy of bioprocessing to be based on solubilization of arabinoxylans, smaller particle size of bran, lower pasting viscosity of starch, improved resistance to extension, and accelerated CO₂ production.     

Effects of Cumin and Ginger as Antioxidants on Dough Mixing Properties and Cookie Quality

The effects of cumin and ginger as antioxidants on dough mixing properties and cookie quality were evaluated. Antioxidant activities in cookies were estimated by total phenolic compounds (TPC) contents and free radical scavenging activities. The cookie dough development was evaluated using Mixolab equipment which showed that addition of cumin did not change dough stability and C2, but decreased C3 and C4. While the addition of 5% ginger decreased dough stability (from 8.4 in the control sample to 6.7 min with 5% ginger addition), C2 (from 0.49 in the control sample to 0.31 N·m with 5% ginger addition), C3, and C4. Cookies formulated with addition of cumin and ginger had increased spread ratios, were softer, and had lower L* and b* values (were darker) than the control. Sensory analysis showed that cookies with cumin and ginger additions had overall acceptability similar to that of the the control with a slightly darker appearance, as confirmed by color determination. Using cumin and ginger significantly increased TPC contents from 78.5 in the control to 93.0 and 109.8 mg of gallic acid equivalent/100 g, respectively. Similar results were observed in the antioxidant activity measured by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), which increased from 41.0% in the control to 51.5% and 64.6%, respectively, for cookies with 5% addition of cumin and ginger.     

Structural Modifications of Gluten Proteins in Strong and Weak Wheat Dough During Mixing

The network‐forming attributes of gluten have been investigated for decades, but no study has comprehensively addressed the differences in gluten network evolution between strong and weak wheat types (hard and soft wheat). This study monitored changes in SDS protein extractability, SDS‐accessible thiols, protein surface hydrophobicity, molecular weight distribution, and secondary structural features of proteins during mixing to bring out the molecular determinants of protein network formation in hard and soft wheat dough. Soft wheat flour and dough exhibited greater protein extractability and more accessible thiols than hard wheat flour and dough. The addition of the thiol‐blocking agent N‐ethylmaleimide (NEM) resulted in similar results for protein extractability and accessible thiols in hard and soft wheat samples. Soft wheat dough had greater protein surface hydrophobicity than hard wheat and exhibited a larger decrease in surface hydrophobicity in the presence of NEM. Formation of high‐molecular‐weight (HMW) protein in soft wheat dough was primarily because of formation of disulfides among low‐molecular‐weight (LMW) proteins, as indicated by the absence of changes in protein distribution when NEM was present, whereas in hard wheat dough the LMW fraction formed disulfide interaction with the HMW fraction. Fourier transform infrared spectroscopy indicated formation of β‐sheets in dough from either wheat type at peak mixing torque. Formation of β‐sheets in soft wheat dough appears to be driven by hydrophobic interactions, whereas disulfide linkages stabilize secondary structure elements in hard wheat dough.     

Effect of Foliar Sulfur and Nitrogen Fertilization on Wheat Storage Protein Composition and Dough Mixing Properties

Nitrogen (N) and sulfur (S) supplies have a strong influence on the quality and quantity of wheat storage proteins, which play an important role in the breadmaking process. Nitrogen derived from urea, S from micronized elemental sulfur, and a mixture of both (N+S) were applied at anthesis stage on wheat by foliar spray. To relate N and S incorporation in storage proteins to the quality of dough, their incorporation into each storage protein fraction was measured: monomers, low molecular weight glutenin subunits (LMW‐GS), and high molecular weight glutenin subunits (HMW‐GS). Then protein fraction quantities, molecular weight distribution (MWD), polymerization index (PI), and molecular dimensions of unextractable polymeric protein (UPP), as well as dough mixing properties were determined. Fertilizers N and S were differentially incorporated into each storage protein fraction, influencing protein synthesis. Moreover, after the N+S fertilization, the increase of the polymeric proteins induced an increase in molecular weight and compactness, as well as in dough strength and consistency. These results provide evidence that N and S fertilizers applied by foliar spray route at anthesis, simultaneously, play an important role in controlling the storage protein synthesis and the degree of polymerization, which in turn influence dough mixing properties.     

Flour Characteristics Related to Optimum Water Absorption of Noodle Dough for Making White Salted Noodles

Physicochemical properties of 34 wheat flours with various classes and different protein contents were related to optimum water absorption of noodle dough. Club and soft wheat flours generally exhibited higher water absorption (34–37%) of noodle dough than hard wheat flours (31–35%). Optimum water absorption of noodle dough in three hard wheat flours with five different protein contents was 33–37%. Optimum water absorption was negatively correlated with flour protein content and SDS sedimentation volume. Physical properties of flour, damaged starch content, NIRS hardness and water retention capacity, influenced optimum water absorption of noodle dough from club, soft and hard wheat flours. A prediction equation developed using protein content, water retention capacity and SDS sedimentation volume of flour provides a reliable estimation of the optimum absorption of noodle dough for making noodles.     

Link Between Mixing Requirements and Dough Strength

Industrial bakeries in Australia and New Zealand using the mechanical dough development (MDD) process have experienced undesirable increases in dough mixing requirements. This problem is an unwanted outcome of breeding programs that have endeavored to increase dough strength as a desirable characteristic. Research was undertaken to determine the nature of the link between dough strength and mixing requirements and its relevance to the MDD process across a wide range of wheat lines. Data from three similar trials of 20 wheat lines confirmed the existence of an apparently tight, positive correlation between mixing requirements and dough strength. Although a wide range in genotypes and environments was used, no significant outliers were found, despite the belief that the link between these quality attributes was breakable or at least flexible. This creates a dilemma, as it would be desirable to reduce work input (WI) for economic reasons but not at the expense of loaf quality, which could have a deleterious effect on product marketability. The resultant nexus between mixing requirements, as measured by MDD WI, and dough strength measured by extensigraph resistance to extension (Rmax), appeared to be influenced by the application of nitrogen fertilizer during cultivation, while the nexus between mixing requirements as measured by mixograph development time (MDT) and Rmax, was influenced by other factors associated with crop location. The nexus between farinograph development time (FDT) and Rmax was affected by both location and nitrogen fertilizer application. The rates of increase in WI, MDT, and FDT against Rmax appeared to differ between high molecular weight glutenin subunits (HMW-GS) 5+10 or 2+12 (the Glu-D1 alleles). The Glu-A1 and Glu-A3 loci also played a significant role, indicating that by manipulating them it may be possible to shift or manipulate the nexus between mixing requirements and dough strength. Alleles at these loci appeared to be additive in effect on WI, MDT, and FDT, as well as Rmax.     

Determining Wheat Dough Mixing Characteristics from Power Consumption Profile of a Conventional Mixer

A Hobart mixer with a pin‐type attachment was used to mix soft wheat flour dough. Power consumption profiles were measured continuously during mixing for 20 min using a current transducer and a data logging system. Experimental variables were quantity of flour (500, 1,000, and 1,500 g of dry wheat flour), water content (43, 45, and 47%, wb), and mixer speed setting (low, medium, and high). The power consumption profiles were evaluated by moving average and spectral analysis. Peaks in the power consumption profiles were located to determine the optimal mixing time. The optimal mixing times were then compared with storage and viscous moduli measured using a dynamic rheometer to assure the maximum strength of wheat dough at the optimal mixing time. Tolerance was determined using the signal amplitude and phase angle data from spectral analysis. Optimal mixing times of various doughs at medium speed ranged from 510 to 850 sec; low and high flour quantities required longer mixing times than medium quantity of flour. The optimal mixing time increased when the moisture content was lowered. Tolerance was affected by mixing speed and moisture content of flour     

Structural Modification of Gluten Proteins in Strong and Weak Wheat Dough as Affected by Mixing Temperature

The effects of temperature (≥25°C) on dough rheological properties and gluten functionality have been investigated for decades, but no study has addressed the effect of low temperature (<30°C) on gluten network attributes in flours with strong and weak dough characteristics. This study monitored changes in protein extractability in the presence and absence of reducing agents, the contents of readily accessible and SDS‐accessible thiols, and the secondary structural features of proteins in doughs from commercial hard wheat flour (HWF) and soft wheat flour (SWF) mixed at 4, 15, and 30°C. SWF mixed at 4 and 15°C showed similar mixing properties as HWF mixed at 30°C (which is the standard temperature). The effect of mixing temperature is different at the molecular level between the two flours studied. Protein features of HWF did not change as mixing temperature decreased, with the only exception being an increase in SDS‐accessible thiols. Decreasing mixing temperature for SWF caused an increase in SDS protein solubility and SDS‐accessible thiols as well as an increase in β‐turn structures at the expense of β‐sheet structures. Thus, noncovalent interactions appear to drive protein network at low temperatures (4 and 15°C), whereas covalent interactions dominate at standard mixing temperature (30°C) in doughs from both flours.     

Genetic and Environmental Effects on Dough Mixing Characteristics and Agronomic Performance of Diverse Hard Red Winter Wheat Genotypes

Wheat (Triticum aestivum L.) genotypes with short mixing times usually have low mixing tolerance values, which make them more sensitive to overmixing in commercial bread production. In this study, we evaluated the genotypic and environmental effects on agronomic performance and end‐use quality of 27 experimental genotypes (hereafter referred to as mixing tolerant genotypes) which were identified in an initial screen as having short mixing times and good mixing tolerances to 1) determine whether genotypes identified in a preliminary end‐use quality screen as lines with usually long tolerances but short mixing times were due to their genotype (G), the environment (E), or G × E; and as these results were unusual, 2) determine whether or not our initial screen predicts end‐use quality, and 3) determine the stability of both agronomic and end‐use quality traits. The 27 genotypes and five check cultivars were grown in a randomized complete block design with two replicates in nine environments in 1997 and 1998. All plots were harvested for grain yield. The harvested grain from the first replicate and random genotypes from the second replicate were micromilled to produce flour samples for evaluation of flour yield, protein content, and mixograph mixing time and mixing tolerance values. Seed diameter, thousand kernel weight, and kernel hardness were also measured in three environments. Environment, G, and G × E interaction effects (mainly changes in magnitude) were significant for most agronomic and end‐use quality parameters. Our initial screen, which had identified 27 genotypes, was partially effective in identifying genotypes that have shorter mixing time values compared with their mixing tolerance values. We identified four genotypes (15%) from the mixing tolerant genotypes that had a good mixing tolerance value and relatively shorter mixing time, as did the released cultivars ‘Agate’ and ‘Scout 66’. However, mixing characteristics values of all genotypes fell within the acceptable limits, indicating our screen effectively identified genotypes with acceptable quality. Mixing tolerant genotypes, which had been identified as having short mixing time scores and long mixing tolerance scores, were considered stable across environments.     

Ultrasonic Investigation of the Effect of Mixing Under Reduced Pressure on the Mechanical Properties of Bread Dough

Mixing is critical to attainment of a desirable gas cell distribution in dough. By varying mixer headspace pressure, changes in the mechanical properties of dough were investigated as a function of the dough's void concentration using low frequency (50 kHz) ultrasonic techniques. For the mixer used, this allowed the volume fraction of voids (Φ) to be varied from ≈0.01 to 0.08. The ultrasonic attenuation of longitudinal waves increased linearly with increases in Φ. If, as reported, pressure reductions during mixing decrease the number density of the voids but do not affect void size, the change in attenuation is proportional to the number of voids. By contrast, the velocity of longitudinal ultrasonic waves decreased dramatically with increasing Φ in the range 0.012 < Φ < 0.03, dropping from a value near that of water to values well below the velocity of sound in air. At higher Φ, the velocity decrease was less rapid. The longitudinal elastic modulus determined from these ultrasonic results shows that the mechanical properties of the dough are sensitive to the presence of gas bubbles. At low void fractions, the elastic behavior of dough is also influenced by changes in dough matrix properties.     

Effects of Mixing Conditions on Pasta Dough Development and Biochemical Changes

Mixing of commercial durum wheat semolina with water was performed under different conditions in a Brabender micromixer equipped with pastamaking shafts. Semolina filling of the mixing chamber was 30.4–42.9% (v/v), shaft speed was 10–110 rpm, temperature was 10–40°C, and hydration level was 47–52.5% (db). The blend of water and semolina evolved from individualized hydrated particles (HP) to a dough product (DP) as a function of these conditions. Torque values (T) and the specific mechanical energies (SME) were recorded during mixing as a function of time. Terms from these curves were defined to characterize the mixing process: t_o (starting time of dough development), t_d (time to reach the maximum dough consistency), T_m (mean torque value after dough development), and SME_f (total energy applied to the dough during mixing). Transformation of HP into DP and the mixing temperature were the main parameters affecting t_o, t_d, T_m, and SME_f. Protein aggregate distribution was measured by size-exclusion HPLC, protein solubility in 0.01N acetic acid, free -SH content, soluble arabinoxylans, reducing sugars, ferulic acid, carotenoid content, and oxidase activities to characterize the biochemical changes that occurred during pasta dough formation. DP was characterized by lower amounts of insoluble glutenin aggregates, lower protein solubility in dilute acetic acid, lower free -SH content, ferulic acid, carotenoid content, and lower oxidoreductase activities as compared to HP. Once the dough was developed, the effects of mixing speed, temperature, or hydration level on the biochemical composition of the blend were null or low compared to the modifications that were observed when the blends changed from HP to DP. The t_o and SME_f were the most significant parameters in characterizing the pasta dough mixing process in relation to biochemical changes.     

Effects of LAB Fermentation on Physical Properties of Oat Flour and Its Suitability for Noodle Making

Flour was obtained from oats fermented with lactic acid bacteria (LAB) to study the effect of fermentation on the physical properties and the suitability of fermented oats for use in starch noodle production. The results showed that fermented samples had a significantly lower pH than control samples. Gel strength and amylose content initially increased and then decreased (P < 0.05) with fermentation time. The peak viscosity, breakdown, final viscosity, and setback value decreased with fermentation time. Fermented noodles showed a higher hardness and springiness. In particular, Lactobacillus plantarum (LP) induced the highest springiness, cohesiveness, gumminess, chewiness, and resilience over 12 hr of fermentation. The cooking quality evaluation indicated that fermentation improved the quality of oat starch noodles. Fermented oats resulted in noodles with low cooking loss and higher cooking weight compared to noodles made from fresh flour. The use of LP for 12 hr of fermentation time yielded noodles of the best quality.     

Relationship of Creep-Recovery and Dynamic Oscillatory Measurements to Durum Wheat Physical Dough Properties

Durum wheat gluten strength is important in determining extrusion properties and pasta cooking quality. Durum wheats varying in strength were tested using an alveograph and a 2-g micro-mixograph, both widely accepted techniques for determination of physical dough properties. Doughs from the 2-g micro-mixograph were characterized by dynamic oscillatory and large deformation creep tests using a controlled stress rheometer. Mechanical properties obtained from both testing regimes were strongly correlated with many of the parameters provided by the alveograph and micro-mixograph. Maximum strain attained after 5 min creep ranged from <5% for the strongest least extensible cultivar to >25% for the weakest cultivar, with a coefficient of variation among replicates of <10%. Storage modulus (G′) at 2 Hz ranged from ≈7,000 Pa for the weakest cultivar to >16,000 Pa for the strongest, least extensible cultivars, with a coefficient of variation of <6%. Tan δ (G″/G′) values were ≈0.4 for the strongest versus >0.5 for the weakest cultivars, indicating the larger contribution of the elastic component in the strong cultivars. The rheometer allows discrimination of durum wheat cultivars of varying gluten strength while requiring less sample than traditional physical dough testing techniques.     

Effects of Cultivar and Temperature During Grain Filling on Wheat Protein Content,Composition, and Dough Mixing Properties

Three wheat cultivars, Bastian, Polkka, and Tjalve, were grown in growth chambers at 9, 12, 15, 18, and 21°C during grain filling in 1994, 1995, and 1996. The wheat samples were analyzed for protein content and sodium dodecyl sulfate (SDS) sedimentation volume. The mixing properties of sifted flours were determined by mixograph, and the flour protein composition was determined by size-exclusion fast protein liquid chromatography (SE-FPLC). The protein content, sedimentation volume, and mixogram parameters were affected by the temperature during grain filling. The protein content increased as the temperature increased. The sedimentation volumes and the mixograph data showed temperature effects that could not be explained by variation in protein content. The proportion of the polymeric flour proteins increased with increasing temperature. Positive correlations were found between the proportion of polymeric proteins and SDS sedimentation volume and, within each year, between the proportion of polymeric proteins and mixograph peak time. Negative correlations were found between the proportion of low molecular weight flour proteins (proportion of fraction IV) and sedimentation volume. The differences in these quality parameters among cultivars exceeded the effect of temperature during grain filling.     

灌浆期高温胁迫对不同品种小麦蛋白组分及面团揉混特性的影响

为研究灌浆期高温胁迫对不同品种小麦蛋白组分及面团揉混特性的影响,以济麦22(JM22)和新麦26(XM26)为材料,通过灌浆初期(S1)和灌浆中期(S2)在田间搭棚进行高温胁迫处理,以未进行高温胁迫的大田小麦作对照(CK),收获后对小麦淀粉黏滞谱、蛋白质组分含量和揉混参数等进行分析。结果表明,与各自CK相比,JM22的黏滞谱参数除回复值和糊化温度降低外,其余参数均升高,XM26的黏滞谱参数除峰值时间外均降低。S1和S2使JM22的峰值黏度、低谷黏度、崩解值、最终黏度、峰值时间分别较CK提高2.81%和18.63%、7.71%和19.51%、11.88%和21.15%、1.88%和12.22%、2.45%和4.08%,且S2均大于CK和S1,S1与CK差异不显著;S1和S2使XM26的峰值黏度、低谷黏度、最终黏度、回复值分别较CK降低12.95%和31.21%、1.81%和27.18%、2.50%和22.22%、3.57%和14.39%,其中,S2、S1与CK三者之间的峰值黏度均达显著水平。与CK相比,高温胁迫后JM22的蛋白质含量降低,而XM26升高。两品种各组分蛋白含量均发生改变,S...     

Influence of Sodium Caseinate and Whey Protein on Baking Properties and Rheology of Frozen Dough

Dairy ingredients are added to bakery products to increase nutritional and functional properties. Sodium caseinate (SC) and whey protein concentrate (WPC) were incorporated into frozen dough. WPC was subjected to heat treatment (WPCHT) to eliminate undesirable weakening of the gluten network. 2% SC or 4% SC decreased proof time, increased loaf volume, and improved texture. Effects of adding 4% SC on baking quality were similar to adding ascorbic acid (AA) and diacetyl tartaric acid esters of monoglycerides (DATEM). WPC increased proof time, decreased volume, and negatively affected texture. Heat treatment of WPC improved baking performance. Bread with WPCHT had volume similar to that of the control without dairy ingredients. Adding 4% SC decreased resistance to extension (R_5cm measured with the extensigraph), while adding 4% WPC increased extensibility. Dynamic oscillation testing determined the effects of the ingredients on fundamental rheological properties. WPC decreased storage modulus (G′) and loss modulus (G″), while heat treatment of WPC increased G′ and G″. Confocal laser scanning microscopy (CLSM) showed that milk proteins affect frozen dough ultrastructure. Frozen doughs with SC had an enhanced gluten network compared with the control, while untreated WPC appeared to interfere with the gluten network.