Accelerated ageing of wheat grains: Part II-influence on thermal characteristics of wheat starch and FTIR spectroscopy of gluten

Wheat quality characteristics are influenced by different factors such as moisture content, storage time and temperature. In this study accelerated ageing of wheat grains was carried out by increasing moisture content (16, 18 and 20%) and keeping the samples in different temperatures (30, 40 and 50 °C) for different periods (2, 5 and 8 days). After milling, the thermal properties of starch and structure of gluten were investigated using Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR); respectively. The experimental set up was designed using response surface methodology and the three distinct factors were combined by central composite design. Results showed that increasing moisture content caused a decrease in onset, peak and end set temperatures of gelatinization while increasing storage time and temperature increased these parameters. By progressing storage time the band intensity of thiol groups decreased while that of disulfide groups of gluten increased indicating an improvement in gluten quality. Increasing moisture content from 16 to 20% and higher storage temperature (50 °C) decreased intensity of disulfide bands.     

Effect of extrusion cooking of sorghum flour on rheology,morphology and heating rate of sorghum–wheat composite dough

Addition of a gluten-free flour such as sorghum has negative impact on the quality of wheat dough for bread making. One of the methods which can be used to promote the quality of sorghum-wheat composite dough is to extrude the sorghum flour before incorporation. In this regard, to produce a dough with appropriate bakery properties sorghum flour was extruded at 110 °C and 160 °C die temperature with 10%, 14% and 18% feed moisture. The effect of extruded sorghum flour incorporation (10%) on rheological (farinography and stress relaxation behavior), morphological and temperature profile of sorghum-wheat composite dough were evaluated. Extrusion cooking altered the sorghum-wheat composite dough properties through partial gelatinization of starch granules. Addition of extruded sorghum flour increased the water absorption and dough development time but it decreased the dough stability. Native sorghum-wheat composite dough showed viscoelastic liquid-like behavior whereas addition of sorghum flour extrudate changed dough to a more viscoelastic solid-like structure. Maxwell model was more appropriate than Peleg model to describe the viscoelasticity of the sorghum-wheat composite dough. Extrusion cooking decreased composite dough elasticity and viscosity. Sorghum extrudate increased the heating rate of composite dough crumb during baking. Addition of extruded sorghum flour formed a non-uniform and less compact dough structure. As a result, dough containing extruded sorghum flour had a good potential for producing a high-yielding bread in a short time of baking.     

Effect of wheat germ flour addition on wheat flour,dough and Chinese steamed bread properties

Wheat germ flour (WGF) has been developed as a functional food ingredient with high nutritional value. In this study, WGF was applied in steamed bread-making in order to improve the quality of Chinese steamed bread (CSB). Partial substitution of wheat flour with WGF at levels of 3%, 6%, 9% and 12% (w/w) was carried out to investigate physicochemical properties of blends and their steaming performance. Falling number (FN) values of composite flours ranged from 199 to 223 s. Viscosity analysis results showed that wheat flour mixed with WGF had higher pasting temperature and lower viscosities. Dough rheological properties were also investigated using farinograph and extensograph. The addition of WGF diluted the gluten protein in dough and formed weak and inextensible dough, which can be studied by scanning electron microscope (SEM) analysis. CSB made with WGF had significantly lower volume, specific volume and higher spread ratio. The sensory acceptability and physicochemical quality of CSB were improved with the application of a low level of WGF (3% and 6%). However, results showed that a high level of WGF over 9% is not recommended because of unsatisfactory taste. As a whole, addition of appropriate level of WGF in wheat flour could improve the quality of CSB.     

食用胶对小麦粉面团流变学特性的影响

为明确食用胶在面制食品中的作用,以3种商业小麦粉(特一粉、富强粉、上白粉)为试验材料,分别添加不同比例的海藻酸钠、黄原胶、卡拉胶,分析其对面团流变学特性的影响。结果表明,小麦粉添加0.15%~0.25%的海藻酸钠,面团稳定时间显著提高,弱化度显著降低;添加0.10%、0.20%和0.25%的海藻酸钠,面团最大拉伸阻力显著提高。添加0.02%、0.06%和0.10%的黄原胶,面团最大拉伸阻力显著提高;添加0.10%黄原胶的面团拉伸面积也显著提高。添加0.10%的卡拉胶,面团稳定时间、拉伸面积显著提高,弱化度显著降低。食用胶因小麦粉品质不同对面团流变学特性的影响也不同,除添加0.25%的海藻酸钠外,其他添加量的3种食用胶均可降低特一粉的面团吸水率,提高上白粉的吸水率。研究认为,海藻酸钠、黄原胶、卡拉胶可显著改善小麦粉的面团流变学特性,增强面团筋力。     

Effects of wheat tempering and stone rotational speed on particle size,dough rheology and bread characteristics for a stone-milled weak flour

The poor technological performance of weak wheat flours means that they are usually considered difficult to be transformed into satisfactory bread. During milling, there are several settings that can affect flour characteristics. In this study, we tested two operative parameters that have the potential to affect flour quality – stone rotational speed and wheat tempering. Tempering moistures were set at 11%, 13%, 15%, and 17%, while stone rotational speeds were set at 173, 260, and 346 rpm. Both factors were found to affect operative milling parameters, notably flour yield, process productivity and specific energy consumption. Grain moisture had a significant effect on both dough rheology and bread characteristics (dough stability, tenacity, and extensibility). Dough stability was maximum at 13% moisture. Dough tenacity decreased as moisture increased, while extensibility increased as moisture increased. Bread specific volume and crumb specific volume were improved at 13% and 15% moisture. In conclusion, wheat tempering can be used to improve the potential of a weak flour and bread characteristics, while stone rotational speed affects operative parameters and white flour yield.     

甘肃冬小麦品种品质性状分析与评价

为了全面掌握甘肃冬小麦的品质状况,以甘肃省冬小麦主产区100个小麦品种(系)为供试材料,采用AACC国标分析方法对其籽粒蛋白质品质、磨粉品质及面团流变学特性进行检测和分析。结果表明,甘肃冬小麦品种具有较高的蛋白质、湿面筋含量和吸水率,但面筋强度较低,形成时间、稳定时间较短,最大抗延阻力和拉伸面积较小,加工品质与国内主产麦区存在一定的差距,商品率低。甘肃冬小麦品种整体以中筋小麦为主。建议在今后育种过程中加强对品质性状的选择,以进一步提升小麦品种质量水平。     

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。     

Effect of NaCl on rheological properties of dough and noodle quality

To assess the effect of NaCl on processing properties of different varieties of wheat flour and noodle quality, the rheological properties of dough, and the quality of white salted noodles made from three different varieties of wheat flour were evaluated. The results showed that the addition of NaCl had different effects on the rheological properties of different varieties of wheat flour. As NaCl concentration increased, the stability time of both intermediate-gluten and weak-gluten wheat flour increased, while that of strong-gluten wheat flour increased initially and then remained stable. The developing time of strong-gluten wheat flour increased, while those of both intermediate-gluten and weak-gluten wheat flour did not change significantly. The energy values of intermediate- and weak-gluten wheat flour did not change significantly while that of strong-gluten wheat flour increased. NaCl had no apparent effects on the hardness, springiness, gumminess, chewiness and resilience of noodles. The cooking loss of fresh noodles increased positively with increasing NaCl concentration. Microstructure of noodles showed that gluten network structure of noodles became more and more dense with increasing NaCl concentration. The effect of NaCl on gluten protein contributed to the change of rheological properties and noodle quality.     

Comparative analysis of dough rheology and quality of bread baked from fortified and high-in-fiber flours

The research, evaluated the rheological properties of dough and final bread quality production, in function of time, made from wheat refined flour that was enriched with an oat dietary fiber in two dosages (WOF 6% and WOF 12%), spelt flour and two types of wholegrain flour: wholegrain (full milling) and wholemeal (one-step milling). The rheological measurements revealed that the highest instantaneous compliance (J₀) was observed in the wholemeal sample and the lowest was in the WOF 6%. The lowest specific volume was observed in the wholegrain bread (0.82 cm³/g), while the highest was observed in the control white bread sample (1.60 cm³/g). The most rapid loss of moisture appeared in white bread. The moisture content was significantly influenced by the type of flour, day of storage and the interaction of these two variables (p ≤ 0.01). The hardest was the sample of wholegrain bread on the first and third day. The smallest pores were noticed in WOF 12% sample. In water extraction, white bread and WOF 12% were comparable and there were no significant differences between spelt bread and wholegrain bread. THE WOF 12% sample had the optimal ratio of health benefits and technological properties.     

不同种植密度下施肥对强筋春小麦品质形成的调控效应

为给春小麦优质栽培提供依据,以优质春小麦品种龙麦26为材料,分析了不同种植密度下施肥量对强筋春小麦品质形成的调控效应。结果表明,随种植密度的增加,千粒重降低,而籽粒容重增大。种植密度对籽粒蛋白质含量、面筋含量以及面粉品质和面团流变学特性无显著影响。适当增加施肥量可以提高小麦籽粒蛋白质含量和面筋含量,增加沉淀值,改善面粉降落值,提高吸水率,延长面团的形成时间和稳定时间,但对面团的拉伸特性影响不大,并降低了容重和千粒重。     

Comparison of quality of refined and whole wheat tortillas

The use of whole wheat flour instead of refined flour significantly improves the nutritional profile of flour tortillas. However, whole and refined flours differ in properties and in how they process, thus needing process modifications to get the desired product quality. To understand these differences, refined and whole wheat flours, dough and tortillas were evaluated and compared for physical and rheological properties. Overall, whole wheat flour required more water (59% of flour weight) than refined wheat (53%) to make machineable dough. Refined flour doughs were more extensible and softer than whole wheat flour doughs, thus easier to process. Whole wheat flour tortillas were larger, thinner and less opaque than refined flour tortillas. In general, refined wheat tortillas were more shelf-stable than whole wheat tortillas. Smaller particle size and less fiber in the refined wheat flour mainly contributed to the observed differences. Among the whole wheat samples, tortillas from strong flours had excellent shelf-stability, which must be considered when whole wheat tortillas are processed. This will minimize the need to add vital wheat gluten or other dough strengtheners.     

Effect of barley and oat flour types and sourdoughs on dough rheology and bread quality of composite wheat bread

The potential of sourdough to improve bread quality of barley and oat enriched wheat breads may depend on the characteristics of the added flour (cereal type, variety, extraction rate). We compared the effect of different barley flours and oat bran (substitution level 40%), unfermented and as sourdoughs (20% of total flour), on composite wheat dough and bread characteristics by combining empirical rheological analyses (DoughLab, SMS/Kieffer Dough and Gluten Extensibility Rig) with small-scale baking of hearth loaves. Whole grain barley flour sourdough increased resistance to extension (Rmax) of the dough and improved the form ratio of hearth loaves compared to unfermented whole grain barley flour. However, sourdough showed little effect on the breads prepared with sifted barley flour or oat bran. The breads made with oat bran showed highest bread volume, lowest crumb firmness and highest β-glucan calcofluor weight average molecular weight (MW). The heat treatment of oat bran inactivated endogenous enzymes resulting in less β-glucan degradation. High MW β-glucans will increase the viscosity of the doughs water phase, which in turn may stabilise gas cells and may therefore be the reason for the higher bread volume of the oat bran breads observed in our study.     

Genetic control of processing quality in a bread wheat mapping population grown in water-limited environments

End-use quality of bread wheat (Triticum aestivum L.) is affected by both genetic and environmental variation. Current understanding of the genetic control of wheat quality traits is mainly based on genetic experiments conducted using grain produced in favourable conditions. The objective of this research was to extend the genetic analysis of these traits by using grain produced in water-limited environments. Grain samples harvested from a mapping population grown in field experiments at two locations in Australia were used to assess characteristics of the grain, flour, dough and bread. Quantitative trait loci (QTLs) were mapped. The parents of the population, RAC875 and Kukri, differ at several loci that are known to affect grain quality or plant phenology. Of these, a high-molecular-weight glutenin locus (Glu-B1) affected dough properties, the puroindoline-encoding Ha locus affected grain hardness, flour and loaf properties and a photoperiod response locus (Ppd-D1) affected flour extraction and protein content. Similarly, several previously reported quantitative trait loci (not associated with specific genes) also had effects in the stress environments used here. In addition, novel loci were detected for bread wheat quality traits; their effects may be specific to materials grown in water-limited environments.     

Assessment of antioxidant activity and rheological properties of wheat and buckwheat milling fractions

This study examined the antioxidant properties of the ethanolic extracts of wheat milling fractions (wheat flour type 500 and type 850, and bran) and their polyphenol and tocopherol content, and rheological characteristics of wheat dough supplemented with buckwheat flours (light and wholegrain). The results obtained in this study were correlated with our previously published data on wheat flour type 400, wholegrain wheat flour and buckwheat flours.Buckwheat flours exhibited significantly higher (P < 0.05) antiradical activity on hydroxyl (OH), superoxide anion (O₂⁻) and (1,1-diphenyl-2-picrylhydrazyl) DPPH radicals, antioxidant activity and reducing power than all investigated wheat milling fractions when their corresponding IC₅₀ values were compared.The rheological parameters of wheat dough supplemented with light and wholegrain buckwheat flour (0-50%) were obtained by using Mixolab. Results indicated changes in protein and starch properties of dough.The obtained results indicate the benefit of using buckwheat flours in wheat-based food products, i.e. their contribution in functional and tailor-made-food production.     

Potential use of exogenous lipases for DATEM replacement to modify the rheological and thermal properties of wheat flour dough

The effect of two lipases and DATEM at different concentrations on the rheological and thermal properties of white and whole wheat flour doughs was determined by farinograph, extensograph, texture analyzer and differential scanning calorimetry. Lipases provided similar or better results than that of DATEM on decreasing softening degree and stickiness, and increasing stability, maximum resistance to extension and hardness. Extensibility and energy did not change with lipases, but decreased with DATEM. Lipases and DATEM slightly modified the transition temperatures and enthalpies of ice-melting and starch gelatinization, but significantly increased the moisture and unfrozen water contents, and decreased the solid concentration in unfrozen water. The greatest effect of lipases was observed on decreasing the peak temperature and increasing the enthalpy of amylose–lipid complex dissociation. The changes in the rheological and thermal properties were almost independent of the concentration levels tested, and were mostly reduced when whole wheat flour was used. The improvement in the dough properties by lipases is possibly related to the in situ formation of surface active compounds from endogenous flour lipids. Presumably, these compounds are already located in the right positions in dough, where they might have higher interaction potentials than DATEM with the dough components.     

小麦不同阶段产品品质性状的变异及其关系

为给小麦籽粒、面粉和面团三个不同阶段产品品质性状的改良提供依据以来源于同一组合的48个小麦稳定品系为试验材料,2014-2015年分别在关中东部川道高肥区、关中西部塬区中肥区条件下,研究了小麦籽粒、面粉和面团的12个品质性状在品系间和环境间的变异及其性状间的关系。结果表明,在品系间,籽粒、面粉和面团分别以蛋白质含量、沉降值和最大抗延伸阻力的变异系数最大;在环境间,籽粒、面粉和面团性状则分别以硬度、沉降值和拉伸面积变异系数最大。性状变异在不同产品阶段和条件下表现为：面团>面粉>籽粒,品系间>环境间,品系和环境对大部分性状有极显著影响。籽粒含水量与面粉和面团的大部分性状呈负相关;籽粒硬度与面粉性状指标呈正相关,与面团性状指标相关不显著;籽粒容重对面粉和面团性状影响较小;籽粒蛋白质含量与面粉和面团的多个指标呈正相关。面粉湿面筋含量和面粉沉降值与面团延展性、抗延伸阻力、稳定时间、形成时间和拉伸面积均呈显著正相关;面粉吸水率与面团延展性呈显著正相关。籽粒对面团品质指标的决定系数为0.108 5~0.517 9,面粉对面团品质指标的决定系数为0.618 4~0.873 0。面粉品质较籽粒品质对面团品质影响更大。     

大豆膳食纤维对面团流变学特性及面制品品质影响的研究进展

随着人们对均衡膳食和高品质面制品需求的不断提高,通过添加大豆膳食纤维改良面团流变学特性,进而在一定程度上改良面制品品质成为新的研究热点.该文综述了近年来添加大豆膳食纤维改善面团流变学特性及面制品品质方面的研究进展.同时,归纳了大豆膳食纤维改善面团流变学特性及面制品品质的作用机理,为加工富含大豆膳食纤维的高品质面团及面制...     

Bread-making performances of durum wheat semolina,as affected by ageing

The present study addresses the influence of ageing on the bread-making performances of durum wheat semolina by bread image analysis. Bread loaves were produced from semolina samples stored in 4 different packaging materials for up to 150 days. Sampling and bread-making trials were performed every 15 days. Results showed that ageing does affect durum wheat semolina bread-making performances, highlighting that storage time, rather than the type of packaging material, is the main factor determining quality changes in the final bread samples. In particular, a change in the crust colour parameters and a reduction of the bread slice area and height by 20–35% were observed with increasing semolina storage time, along with a slight increase of crust % area. The change in farinographic parameters of dough suggests that the observed reduction of technological quality might be due to increased stiffness and reduced extensibility of gluten occurring in aged semolina. Unlike common wheat flours, which usually improve their technological features during ageing, durum wheat semolina is negatively affected in its quality by storage. The study highlights the importance of considering bread-making performances among the quality parameters to be taken into account for the shelf life evaluation of durum wheat semolina.     

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.     

土壤相对含水量对冬小麦氮素积累、蛋白质组成和加工品质的影响

为了解土壤相对含水量(SRWC)对冬小麦氮素利用和籽粒品质的影响,在防雨条件下,以高产强筋小麦品种皖麦38为材料,采用测墒补灌的方法,0~40cm土层SRWC在拔节期(J)设置65%、70%和75%3个水平,开花期(A)设65%和70%两个水平,分析了不同处理(分别用J65A65、J65A70、J70A65、J70A70、J75A65、J75A70)间冬小麦氮素积累、蛋白质组成和加工品质的差异。结果表明,在65%~75%范围内,随拔节期SRWC的提高,小麦开花期各器官的氮素积累量显著增加;J70A70处理的成熟期籽粒氮素积累量与J75A65和J75A70处理无显著差异,但显著高于其他处理,且其氮素收获指数最高。开花期SRWC相同时,拔节期SRWC 65%处理较SRWC 70%处理具有较高的贮藏蛋白含量和谷醇比以及较低的可溶性蛋白含量;J65A65处理的籽粒谷蛋白含量、谷醇比和贮藏蛋白占总蛋白的比例显著高于其他处理。与面粉品质和烘烤品质相比,拔节期和开花期SRWC对面团品质的调控效果明显。其中,面团形成时间和稳定时间在拔节期SRWC 65%和70%条件下随开花期SRWC的提高而降低;开花期SRWC相同时,拔节期SRWC 65%处理较SRWC 70%和75%处理提高了面团形成时间、稳定时间、沉降值、面包体积。综合以上结果,J65A65处理提高了籽粒谷蛋白和谷醇比,延长了面团形成时间和稳定时间,增加了面包体积,有利于改善冬小麦加工品质,是最佳的优质节水测墒补灌方案。