Effects of potato/wheat flours ratio on mixing properties of dough and quality of noodles

The effects of potato flour/wheat flour (PF/WF) ratio on the mixing properties of dough and the quality of noodles were investigated. Substitution of wheat flour with potato flour caused the increases in the water absorption and the protein weakening value (C1-C2) of formulated flours, as well as the decrease in the corresponding dough mixing parameters including dough development time (DDT), dough stable time (DST), initial mixing time (C2), maximum torque during heating (C3), minimum torque of hot paste (C4) and the amount of retrogradation (C5-C4), indicating that the addition of PF weakened dough strength but improved degradation resistance. The textural, cooking, sensory characteristics and microstructure of noodle samples were evaluated. The results indicate that adhesiveness, springiness, broken ratio and cooking lose increased progressively with increasing PF content while the score of sensory evaluation continued to decrease. However, hardness, cooking yield and optimum cooked time for the samples of PF content range from 10% to 20% showed a distinctive variation. Environmental scanning electron microscopy (ESEM) confirmed changes in noodle microstructure as PF addition affected gluten network development. In general, noodles with PF content below 40% were acceptable.     

Large deformation stress relaxation and compression-recovery of gluten representing different wheat classes

Despite the great variety of physicochemical and rheological tests available for measuring wheat flour, dough and gluten quality, the US wheat marketing system still relies primarily on wheat kernel hardness and growing season to categorize cultivars. To better understand and differentiate wheat cultivars of the same class, the tensile strength, and stress relaxation behavior of gluten from 15 wheat cultivars was measured and compared to other available physicochemical parameters, including but not limited to protein content, glutenin macropolymer content (GMP) and bread loaf volume. In addition, a novel gluten compression–relaxation (Gluten CORE) instrument was used to measure the degree of elastic recovery of gluten for 15 common US wheat cultivars. Gluten strength ranged from 0.04 to 0.43 N at 500% extension, while the degree of recovery ranged from 5 to 78%. Measuring gluten strength clearly differentiated cultivars within a wheat class; nonetheless it was not a good predictor of baking quality on its own in terms of bread volume. Gluten strength was highly correlated with mixograph mixing times (r = 0.879) and degree of recovery (r = 0.855), suggesting that dough development time was influenced by gluten strength and that the CORE instrument was a suitable alternative to tensile testing, since it is less time intensive and less laborious to use.     

燕麦粉对强筋面粉品质特性及其面包品质的影响

面包逐渐成为中国人营养早餐的选择,但面包中膳食纤维含量较低。燕麦是一种食疗兼备的特色杂粮作物,富含膳食纤维。为拓宽燕麦的应用范围、提高面包的营养价值,以优质强筋小麦品种藁优2018和燕麦粉为材料,研究了燕麦粉对小麦面粉面团流变学特性及淀粉糊化特性的影响,并进行了燕麦面包实验室制作和质构分析。结果表明,随着燕麦粉添加比例的增加,面团吸水率逐渐增加,面团稳定时间和粉质质量指数先减小后增加;面团拉伸能量、拉伸长度、拉伸阻力、最大拉伸阻力均逐渐减小。说明燕麦粉对面团拉伸特性各参数均有弱化作用。在藁优2018小麦面粉中添加10%的燕麦粉,既能保证面包的感官品质,又能满足面包营养最大化。     

Development of a standard test for dough-making properties of oat cultivars

Bread is consumed all over the world. However, so far, production of large volume bread is only possible with wheat. Alternatives, such as oats, are less suitable but this is partly due to the lack of knowledge about their functionality for other purposes than porridge, which is their most common use. Existing standard tests for the dough making characteristics of wheat flour are not suitable for oat flour, hampering research to optimize oats for bread-making purposes. We therefore set out to develop a test to evaluate oat in relation to mixing and dough making properties using wheat as a model. It was possible to reproduce the profile of various qualities of wheat flour using mixtures of oat flour and gluten in different proportions. Our standard test was based on a dough system composed of 87.2% oat flour and 12.8% gluten and it presented similar properties to a wheat flour with regard to resistance to extension. This dough system was sensitive and reliable (coefficient of variation lower than 10%) for detecting differences among oat cultivars, and it can be used to screen oat varieties and individual oat components in relation to relevant properties for bread-making purposes.     

不同小麦粉混配品质性状的变化

为了研究小麦粉混配过程中品质性状的变化，分析了陕西省13个推广小麦品种及其23种混配粉的蛋白质品质和面团流变学特性。结果表明，强筋小麦不同批次制粉品质变化较大，中筋和弱筋小麦品质变化相对较小，不同方式配粉面团流变学特性变化规律不同。强筋 中筋和强筋 弱筋两种方式配粉稳定时间测定值比理论值减少，延伸性有增有减。同时，强筋 中筋=强筋的配粉延伸性以减小为主，而强筋 中筋=中筋的配粉延伸性增加，2个中筋粉或中筋与弱筋粉混配延伸性明显增加。混配粉面筋含量、沉淀值、稳定时间和延伸性测定值与由基础品种估算的理论值无显著差异，而且呈极显著正相关，相关系数分别为0．9818^**、0．9776^**、0．8594^**和0．7189^**。文中还提出了根据配粉需要估算基础品种混配比例的方法。     

Dough and bread made from high- and low-protein flours by vacuum mixing: Part 1: Gluten network formation

The effects of reduced headspace pressure on the development of gluten network in doughs made from both high-protein flour (HPF) and low-protein flour (LPF) were investigated. The effect of vacuum mixing was found to be dependent on both flour-type and mixing-time. A significant increase in dough extensibility was observed when the HPF dough was mixed under moderate vacuum of −0.04 MPa for 3 min as compared to the one mixed under atmospheric pressure for the same duration. This was attributed to the formation of a more extensive gluten network associated with an increased disulphide bond density and a significantly higher β-sheet to β-turn ratio. On the other hand, over-mixing was observed in the LPF dough that was mixed for 5 min under atmospheric pressure. Applying moderate vacuum of −0.04 MPa allowed the LPF dough to withstand longer mixing time, as indicated by its increased disulphide bond density and biaxial extensibility compared to the control dough mixed under atmospheric pressure. Results of this study suggest the potential of applying vacuum to reduce the mixing time required for high protein flour and to prevent the over-mixing of low protein flour.     

Correlation of glutenin macropolymer with viscoelastic properties during dough mixing

Although significant correlations exist for glutenin macropolymer (GMP) quantity and rheological properties/bread making quality of dough, little information about these links is available. The relationship between GMP contents measured by UV absorption method/RP-HPLC and dough viscoelastic properties determined by TA-XT2i texturometer from three wheat varieties (Xiaoyan6, Yumai56 and Zhengnong8805) during mixing was investigated. GMP contents of doughs decrease significantly (P<0.05) during mixing. During the initial mixing stage, amounts of the HMW-GS and LMW-GS and GMP decrease significantly (P<0.05). Their contents begin to increase beyond peak dough development time (DDT). This indicates that during further mixing after peak DDT some glutenin subunits are incorporated into GMP by repolymerization. The HMW/LMW-GS ratio has a significant effect on load-deformation properties (area, resistance and extensibility) of dough. The varieties behaved differently in relation to the contribution of their HMW-LMW-GS ratio to the rheological properties.     

Correlations of the Breadmaking Performance of Wheat Flour with Rheological Measurements on a Micro-scale

For the characterization of wheat quality, micro-extension tests for dough and gluten and a micro-baking test were developed using comparable dough compositions, the same mixing temperature and cultivar-specific mixing times. By means of these methods, the flours of 26 wheat samples were studied for dough development time, maximum resistance and extensibility of dough and gluten and loaf volume of the baked products. Standard methods (rapid-mix-test, gluten index determination) were used for comparison. The results indicated that the rheological properties of dough and gluten as well as the gluten index are correlated higher with the optimised micro-baking test than with the standard baking test. If flour protein or wet gluten content is included in the correlations, the extension test of gluten, which can be performed easily and reproducibly, allows a reliable prediction of the loaf volume obtained by the micro-baking test.     

Preparation and characterization of gluten-free sheeted doughs and noodles with zein and rice flour containing different amylose contents

This study aimed to explore the feasibility of zein as a gluten alternative in preparing sheeted doughs with rice flours containing different amylose contents (12, 19, and 26%) that were successfully slit into noodle strands. Rice-zein mixtures with lower amylose contents exhibited lower pasting parameters and the high amylose paste samples possessed more elastic properties. Higher water absorption was observed in the low amylose rice-zein mixture whereas the use of zein were effective in increasing the stability of rice dough regardless of amylose content. In case of thermal conductivity, the noodle doughs prepared with high amylose rice-zein mixture had low thermal conductivity, probably implying a long cooking time. The structure of the rice-zein noodles had a tendency to become firmer with increasing levels of amylose by showing greater breaking stress and resistance to extension that could be correlated to reduced cooking loss.     

Mixing behaviour of a zero-developed dough compared to a flour–water mixture

The Z-blade mixing behaviour of zero-developed (ZD) doughs from the flours of two wheat cultivars of different gluten strength was compared to that of conventionally mixed dough made from the same flours. In farinograph experiments, use of ZD dough led to shorter development time (with less energy requirement), less stability time, and consequently earlier breakdown compared to conventional mixing of the corresponding flour–water mixture. Mixing of ZD doughs led to an almost similar decrease of glutenin macro-polymer (GMP) wet weight as that of doughs prepared from flour–water mixtures. However, comparison of wet weight of re-assembled GMP revealed that until time-to-peak (TTP) mixing, there was no difference in GMP recovery with respect to the starting material used in the z-blade mixing experiments. Beyond TTP, recovery of GMP in doughs prepared from both starting materials was reduced. The results of large-strain deformation rheology showed strong visco-elastic behaviour as characterised by the highest values of fracture properties (except ε_H), followed by a decline in those properties upon further mixing for doughs mixed from both flour–water mixture and ZD dough from both types of wheat cultivars. It was concluded that at mixing regimes before TTP, there was no difference between ZD doughs and flour–water mixtures in the mixer. When ZD dough is used as a starting material for dough preparation instead of flour, extra care should be taken not to over-mix the developing dough.     

The effect of mixing on glutenin particle properties: aggregation factors that affect gluten function in dough

Previously we reported that the SDS insoluble gel-layer: the Glutenin Macro Polymer (GMP) can be considered as a gel consisting of protein particles. These glutenin particles have a size of about 10⁻¹–10² μm and consist of HMW-GS and LMW-GS only. In GMP isolates from flour, the particles are spherical. In isolates from dough, glutenin particles have lost this shape. This seems relevant, since mixing disrupts the particles and the mixing energy required for dough development correlated with the glutenin particle size in flour. The question studied in this paper is how changes at a glutenin particle level affected the subsequent process of gluten network formation during dough rest and if this could be used to explain resulting dough rheological properties. To this end, we studied how various mixing regimes affected the dough properties during and after resting (elasticity). We cannot fully explain the differences in the final dough properties observed using parameters such as the quantity of GMP in flour, the quantity of re-assembled GMP in dough and the size of re-assembled glutenin particles. However, other parameters were found to be important: (1) the Huggins constant K′ reflecting the tendency of glutenin particles to interact at level II of the Hyperaggregation model; (2) the composition of glutenin particles affecting the potential to form smaller or larger particles and (3) for over-mixed dough, covalent re-polymerisation at the so-called level I of hyperaggregation. Using these parameters we can better explain dough viscoelasticity after resting.     

Application of solvent retention capacity tests for the prediction of mixing properties of wheat flour

One hundred and ninety-two wheat genotypes including 150 released varieties and 42 germplasm lines were evaluated for solvent retention capacity (SRC) tests using 1 g of flour and 1 g of wholemeal to determine relationships with mixing properties of their doughs. Strong positive correlations (p<0.001) were observed between different SRCs (using both wholemeal as well as flour) and Farinograph water absorption (FWA). In multiple regression analysis, flour water SRC explained 41.2%, sodium carbonate SRC 24.6%, sucrose SRC 20.7% and protein content 13.5% of the total variability (multiple r=0.91) in FWA. The data demonstrated that water absorption is governed mainly to starch damage and pentosan content of the flour. Based on multiple regression analysis an equation was developed to predict FWA and a very high positive correlation (r=0.91) was observed between predicted FWA and actual FWA. LASRC exhibited significant positive correlations (p<0.001) with Farinograph and Mixograph parameters related to gluten strength such as the Farinograph peak time and mixing tolerance index and the mixograph peak time and peak dough resistance. Wholemeal flour SRCs accounted for 48% of the variation in FWA and was highly significant (p<0.001). The average values of FWA of corresponding clusters made using wholemeal and flour SRCs were not significantly different. This demonstrates that wholemeal SRCs together with grain protein content can be used to screen early generation lines for FWA. Since large numbers of diverse genotypes were used in the estimation of various parameters, high correlations observed between SRCs and functional properties including water absorption have obvious implications in breeding programs for the improvement of wheat cultivars.     

Strain Hardening Properties and Extensibility of Flour and Gluten Doughs in Relation to Breadmaking Performance

The mechanical properties of flour–water doughs and hydrated gluten of different wheat cultivars were determined. Measurements were performed at small deformations (dynamic measurements) as well as at large deformations (biaxial extension measurements). Results of dynamic measurements of flour doughs related poorly to breadmaking quality. For hydrated gluten doughs, all having the same water content, it was found that glutens from wheat cultivars with good baking quality had higher values for the storage modulus,G, and lower values for the loss tangent. The relevant type of deformation around an expanding gas bubble is biaxial extension. Wheats with a good baking performance exhibited greater strain hardening and greater extensibility. The differences in strain hardening observed at 20 °C were also present at 55 °C. No clear effects of NaCl or emulsifiers on the biaxial extension properties of flour dough were found. Extensograms as well as Alveograms from the flour doughs showed that, in general, good baking flours exhibited stronger resistance to extension and a greater extensibility, but differences found were not directly related to the results of the baking tests. The results indicate that the baking performance of dough is related to a combination of at least three different rheological characteristics.     

Physico-chemical description of bread dough mixing using two-dimensional near-infrared correlation spectroscopy and moving-window two-dimensional correlation spectroscopy

NIR spectroscopy presents a huge interest in exploring chemical changes during dough mixing. The aim of the present study is to investigate the potential of 2D correlation spectroscopy (2D COS) and moving-window 2D (MW2D) correlation spectroscopy to explore the time dependence of NIR spectral responses during wheat flour dough mixing. NIR spectra were continuously recorded (between 1400 and 2325 nm) during mixing of bread type-dough (based on flour, water and yeast), using an FT-NIR spectrometer with a deported probe. The probe was positioned inside the mixer in contact with the dough. The 2D spectra calculated using raw and second derivative NIR spectra were interpreted in terms of physico-chemical events. Nine different industrial flours were used as raw material to validate the analysis. The results obtained using the 2D COS and the MW2D methods give the possibility to ascribe chemical vibrations (starch, water and gluten) to NIR absorbance changes occurring during dough mixing. The analysis of the NIR spectra identified wavelength shift associated to both dough “free water” and protein secondary structure modifications. During this study, only the MW2D method allowed to identify clearly the time dependence of physico-chemical mechanisms from NIR variation bands.     

Effect of Water Unextractable Solids on Gluten Formation and Properties: Mechanistic Considerations

A miniaturised set-up for gluten-starch separation was used to systematically study the effect of water unextractable solids (WUS) on the formation and properties of gluten. The results showed that WUS not only have a negative effect on gluten yield, but also affect gluten and glutenin macropolymer (GMP) composition and rheological properties. The negative effect of WUS on gluten yield could be compensated for to a large extent, but not completely, by increasing mixing time and mixing water. Adding xylanase can effectively counteract the effect of WUS. On the basis of these results we hypothesize that WUS interfere with gluten formation in both a direct and an indirect way. WUS interfere indirectly by competing for water and thus changing conditions for gluten development. This effect can be corrected for by the combination of adding more 0·2% NaCl solution during dough mixing and a longer mixing time. The particulate nature of WUS requires that the direct effect occurs through an interaction between WUS particles and gluten particles. Both effects of WUS can be counteracted through the use of xylanase.     

Comparison of small-scale and large-scale mixing characteristics: Correlations between small-scale and large-scale mixing and extensional characteristics of wheat flour dough

Mixing measurements provide valuable information about dough strength and stability (STAB) traits. These measurements are important in milling and baking operations, and for varietal selection in wheat breeding programmes. There are several techniques with different sample sizes used for measuring these traits so there is interest in examining the agreement between methods in terms of genotypic (varietal) rankings. This issue has been investigated by using two different mixing methods, a small-scale Mixograph (2 g) and large-scale Farinograph (50 g) using data from a doubled haploid population (190 lines) from a Chara (excellent dough strength)×WW2449 (poor dough strength) cross. The cross was grown in a field trial at the Wagga Wagga Agricultural Institute (WWAI) in 2000. Eleven mixing traits were measured and compared according to a statistical design. The estimated genetic correlation matrix for six of the 11 mixing traits, dough development time (DDT), STAB, mixing tolerance index (MTI), maximum bandwidth (MBW), bandwidth at peak resistance (BWPR) and peak resistance (PR) revealed that for these dough-strength-related parameters, both methods were measuring equivalent traits, although individual parameters had widely different coefficients of variation. In this population, PR was correlated with the extensibility trait length determined by large-scale extension testing. None of the large-scale or small-scale mixing traits was an effective predictor of the small-scale extensibility parameter extensibility at Rmax (Ext_Rmax). The data verified that small-scale Mixograph tests are a robust and efficient alternative to large-scale Farinograph tests for both commercial breeding and research.     

Effects of composition on dough development and air entrainment in doughs made from gluten-starch blends

Gluten and starch are the two main ingredients of a wheat flour dough and it is expected that the extent of air occlusion into the dough would be affected by differences in their relative ratios. The objectives of this paper were to investigate the hydration and development of gluten and how these key events in dough mixing affected air occlusion in gluten-starch doughs. For gluten-starch doughs of the same gluten content, decreasing the water absorption shortened development time and decreased dough density. For formulations of the same water absorption, decreasing the gluten content prolonged the time to development and increased dough density, reflecting less net air entrainment into the dough. The ratios of gluten, starch and water strongly influenced the development of the dough into a good gas-holding material, with the extent of gas entrainment during mixing being evident in measurements of both dough consistency and dough development time.     

Predicting hot-press wheat tortilla quality using flour,dough and gluten properties

A cost-effective, faster and efficient way of screening wheat samples suitable for tortilla production is needed. This research aimed to develop prediction models for tortilla quality (diameter, specific volume, color and texture parameters) using grain, flour and dough properties of 16 wheat flours. Another set of 18 samples was used to validate the models. The prediction models were developed using stepwise multiple regression. Dough rheological tests had higher correlations with tortilla quality than grain and flour chemical tests. Mixograph mixing time and dough resistance to extension (from extensibility test using a texture analyzer) were correlated best with tortilla quality, particularly tortilla diameter (r = −0.87 and −0.86 respectively, P < 0.01). Insoluble polymeric proteins (IPP) and gluten index were significantly correlated with tortilla diameter (r = −0.70 and −0.67 respectively, P < 0.01) and specific volume (r = −0.73, P < 0.01). Tortilla diameter was the quality parameter best explained (R² = 0.86) by the prediction models using mixing time and dough resistance to extension. Rheological parameters such as rupture distance and maximum force were also successfully predicted. These prediction models, developed from linear equations, will be an easy and fast tool for breeders to advance or eliminate wheat lines specifically bred for tortilla production.     

中麦175馒头和面条品质稳定性分析

为给优质小麦育种和生产提供参考依据,以优质小麦新品种中麦175于2010-2011年度在河北和北京14个地点的样品为材料,分析了磨粉品质、面粉和面片颜色、面团流变学和淀粉糊化特性、馒头和面条加工品质。结果表明,中麦175为馒头和面条兼用型优质品种,特点是软质、中偏弱的面筋强度、面粉颜色白,多数品质性状较稳定,籽粒硬度、PPO活性、面片a*值、稳定时间、拉伸面积、延展性和最大抗延阻力的变异系数较大,馒头加工品质地点间变异大于面条。磨粉品质和面团流变学参数对馒头加工品质有显著影响,籽粒硬度和出粉率对馒头表面颜色有显著负向影响,相关系数分别为-0.82(P<0.01)和-0.58(P<0.05);面粉L*值高,馒头加工品质好,二者相关系数为0.72(P<0.01);吸水率与馒头总分呈显著负相关(r=-0.84,P<0.01),稳定时间、拉伸面积、延展性和最大抗延阻力与馒头总分呈显著正相关,相关系数分别为0.85(P<0.01)、0.77(P<0.01)、0.62(P<0.05)和0.70(P<0.01)。降低PPO活性和吸水率,提高蛋白质含量、出粉率和黄色素含量可以改善面粉和面片颜色的亮白度,增加部分黄度,形成消费者可接受的奶白色。淀粉糊化特性对馒头和面条加工品质无显著影响。上述信息对改良小麦品质的稳定性有重要意义。     

Understanding the role of oat β-glucan in oat-based dough systems

B-glucan is one of the components that differentiate oats from other cereals and that contribute to the health-related value of oats. However, so far oats cannot easily be applied in bread-like products without loss of product quality. Here we have studied how the content and viscosity of oat β-glucan affect the technological properties of oat dough in both a gluten-free and a gluten-containing system. In both systems, increasing the β-glucan concentration resulted in an increase of dough stiffness and in a reduction of dough extensibility. β-glucan negatively impacted the elastic properties that additional wheat gluten conferred to oat dough. This effect was smaller for medium-viscosity β-glucan than for high-viscosity β-glucan. Interestingly, dough made from low β-glucan flour (<2%) had increased gas retention capacity. Overall, the impact of β-glucan on the properties of oat dough systems was governed by concentration and viscosity, with or without additional wheat gluten. Our findings indicate that β-glucan is a key component that determines the rheology of oat-based dough systems and, with that, the technological functionality of oat in dough systems.