Stress relaxation of reconstituted cassava dough

The viscoelastic characteristics of reconstituted cassava dough were evaluated using a stress-relaxation test. Cassava parenchyma (peeled root) processed under different cooking conditions and left at either −5 or −20 °C for 24 h was used to obtain flour, which was reconstituted into dough. Two stress-relaxation models (Maxwell two-termed and Peleg) were fitted to experimental data. Both models were valid for quantifying the relaxation behaviour; but the Maxwell model was better to predict experimental data. Most dough rheological attributes depend on the cooking method and the storage temperature. Dough samples made with flour from parenchyma boiled and left at −20 °C for 24 h had higher values of elasticity moduli, higher viscosity values and lower values of Peleg constants.     

小麦粉改良剂对面团流变学特性的影响

采用粉质仪和拉伸仪研究不同面团改良剂单体(酶制剂、氧化剂、磷酸盐)对小麦粉面团流变学特性的影响。结果表明:α-淀粉酶、木聚糖酶和ADA对面团粉质特性有显著影响;木聚糖酶、ADA和Vc对面团拉伸特性有显著影响,且ADA的影响程度较大。随着α-淀粉酶、木聚糖酶和ADA添加量的增加,面团的稳定时间和评价值呈下降趋势,弱化度呈上升趋势。随着木聚糖酶添加量的增加,延伸性呈增大趋势,拉伸比值和最大抗拉伸阻力均呈下降趋势,且变化幅度较大;随着ADA和Vc添加量的增加,延伸性、拉伸比值和最大抗拉伸阻力与添加木聚糖酶时变化趋势相反。焦磷酸钠和三聚磷酸钠对拉伸特性无明显作用,在一定添加量时对面团粉质特性有明显影响。脂肪酶对粉质和拉伸特性影响不明显。     

Rheological and textural properties of lafun,a stiff dough,from improved cassava varieties

We studied the textural and rheological (viscoelastic) properties of fresh lafun dough, a fermented cassava product, and their changes during storage at 45 °C for 5 and 24 h, in order to determine after-cooking storability. Lafun flours were produced from three types of cassava varieties: seven improved white-fleshed varieties, seven improved provitamin A carotenoids (pVAC) varieties and two local white-fleshed varieties; and processed into lafun doughs. Pasting properties of the flours were assessed. Flours from local varieties had pasting profiles with highest viscosities, while pVAC flours had the lowest. The three types of cassava varieties varied significantly in most of their pasting properties. Four promising improved varieties were identified, based on high peak viscosity (55.8–61.5 P) and stiffer texture than local varieties during storage. Undesirable varieties were also found, which softened during storage instead of hardening. Optimum texture of lafun dough was obtained after 5 h of storage.     

低聚木糖对面团热机械特性及冷冻面团发酵流变特性的影响研究

采用Mixolab酶流变分析仪和流变发酵仪研究了低聚木糖对面团热机械特性和对冷冻面团发酵流变特性的影响,结果表明低聚木糖有强化面筋、增加面团耐揉性和耐蒸煮性的作用。引入低聚木糖会使流变发酵仪中的气体释放曲线和面团发展曲线的最大高度以及面团的持气率较空白组有不同程度的提高。     

油脂对面团特性及面制品品质影响研究进展

文章综述了油脂类别、添加量及油脂饱和度对面团特性及面制品品质的影响,指出后续可对有关油脂的内在组分与结构对面团的作用机理,以及油脂、淀粉与蛋白质体系的作用机制进行探究。     

醋酸酯变性淀粉对低筋面团热机械学特性的影响

将荞麦粉与小麦粉以6:4比例混合,制成低筋粉,再将马铃薯醋酸酯淀粉及木薯醋酸酯淀粉按不同比例分别添加到低筋粉中,利用Mixolab混合仪研究两种醋酸酯变性淀粉对低筋粉形成的面团流变及糊化特性的影响。结果表明:两种醋酸酯淀粉都可显著的增强面团的强度及蒸煮稳定性(p<0.05),木薯醋酸酯淀粉可延长面团的形成和稳定时间、减小机械弱化值,而马铃薯醋酸酯淀粉会降低面团的吸水率及热弱化值。      

Thermo‐physical properties of composite bread dough with maize and cassava flours

Composite wheat–cassava and wheat–maize flours were produced in ratio 100:0. 60:40, 50:50, 40:60 and 0:100 respectively. Thermo‐physical properties of bread dough were determined. For wheat –cassava composite bread dough, moisture content ranged between 44.02 ± 2.04 to 51.31 ± 2.99% dry basis (db), density (1035.2 ± 20.4 to 975.6 ± 12.6 kg m^?3), specific heat capacity (2.51 ± 0.61 to 3.01 ± 0.42 kJ kg^?1 K) and thermal conductivity (0.362 ± 0.13 to 0.473 ± 0.12 W mK^?1). While wheat–maize mixture gave 44.14 ± 1.94 to 45.09 ± 1.26%(db) of moisture content, 981.4 ± 16.3–960.4 ± 22.5 kg m^?3 density, 1.77 ± 0.17–2.61 ± 0.63 kJ kg^?1 K specific heat capacity and 0.36 ± 0.07–0.39 ± 0.02 W mK^?1 thermal conductivity. Effects of substitutions was significant on moisture content and thermal conductivity of dough while non significant influence was recorded on density and specific heat capacity at P < 0.05.     

香菇粉对小麦面团热机械学和动态流变学特性的影响研究

本试验通过测定不同比例的香菇粉和小麦粉混合粉的热机械学和动态流变学特性,研究香菇粉对小麦面团特性的影响。结果表明,香菇粉的添加使小麦面团的吸水率增大,面团的形成时间和稳定时间先下降后上升,相应的蛋白质弱化度先升高后降低。香菇粉的添加使小麦面团的峰值黏度和回生值均显著降低。动态流变学试验显示:香菇粉的添加使得小麦面团的黏弹特性发生了显著的变化,储能模量(G')与损失模量(G")均呈现先降低后升高的趋势。而tanδ随香菇粉比例的增大呈现了先略微升高后明显降低的趋势,表明了混合体系中分子交联的程度有所增加,弹性比例增大。     

Mixing properties and rheological characteristics of dough used to make potato‐cereal soft wraps

We have studied mixing, rheology and stability of potato‐cereal flour doughs. These were prepared using samples of two varieties of cooked and cold‐stored potatoes. Dependent on variety a minimum duration of 24–48 h cold‐storage was required. Dough mixing torque plateau was inversely related to potato water content. This should be <79 g/100 g. It was also necessary to have a stable dough mixing torque plateau of >2 Nm at a specific total mechanical energy input of 18–22 kJ kg^?1. The resting temperature of the dough was also inversely related to its strength (plateau elastic modulus at time zero). Target dough strength should be about 25 kPa in a bob‐cup. Above 15 °C it decreased as a function of time and within 1 h it became too sticky for commercial processing. At 4 °C the dough remained stable. Sufficient potato starch retrogradation is a pre‐requisite to make optimal potato‐cereal flour dough for commercial processing.     

百合粉添加量对面团特性及面包品质的影响

为拓宽百合的应用渠道,提高面包的营养价值,研究了百合粉添加量(0%,5%,10%,15%,20%)对面团的微观结构、糊化特性、流变学特性以及面包品质的影响。结果表明:随着百合粉添加量增大,混合粉的持油性先降低后增加,持水性显著增加(P<0.05)。添加了百合粉后,面团的糊化温度升高,回生值和峰值黏度下降,面团的弹性模量和黏性模量均呈上升趋势。百合粉的添加,破坏了面筋蛋白原本均匀致密的微观结构;使面包的硬度显著增大(P<0.05),弹性、内聚性、胶黏性、咀嚼性、回复性、比容和感官评分显著降低(P<0.05);改变了小麦面团的特性和面包的品质,在小麦粉中添加5%～10%的百合粉,能保证面包较高的感官品质。     

Effect of waxy flour blends on dough rheology and bread quality

Although much research has been conducted on wheat flour dough rheology, the principal focus has been the role of the protein fraction. Starch is the main component of flour and plays a key role in dough dynamic properties, particularly during heating. This study assesses the effect of two different waxy flours, a durum and a bread wheat, and their blends with commercial bakers' flour on dough rheology during heating with a concurrent investigation into baking performance. Both waxy flour blends produced similar effects on dough rheological behaviour despite differences in protein content, acting to delay gelatinisation and reduce storage modulus. The main effects in bread were to increase loaf expansion during baking and reduce loaf firmness. It is postulated these effects are largely water mediated, with the higher swelling ability of the waxy starch granules reducing overall water availability and driving complete gelatinisation to higher temperatures.     

维生素C对面团特性影响研究

通过研究Vc对面团特性影响表明,面粉中添加Vc能增加面团吸水率和形成时间,降低面团弱化度,增加面团拉伸面积、拉伸阻力和拉伸比值,降低面团延伸性;其最适添加范围为120～160ppm.     

The effect of different mixing processes on dough extensional rheology and baked attributes

BACKGROUND: Mixing is a significant part of the breadmaking process and is responsible for the development of the essential structure that will facilitate gas retention during proofing and the early stages of baking. The main objective of this study was to examine whether the dough extensional rheological and baking properties were affected from different mixers and energy inputs during mixing. RESULTS: It was found that extensional properties in uniaxial and biaxial extension were affected by the mixing equipment used and by the energy input used. Doughs mixed using a Farinograph had higher maximum resistance to uniaxial extension, higher P value and lower biaxial extensibility (Alveograph) and higher biaxial extensional viscosity than doughs mixed in a Stephan mixer (P < 0.01). The energy input was specific to each type mixing equipment and affected the biaxial extensional viscosity. Also, higher loaf volumes were achieved when higher energy inputs were used, whereas other baking properties were not affected. CONCLUSION: Altering the mixing equipment and the mixing speed affected the rheological properties of dough. Dough development during proofing as well as loaf volume was affected by the energy input levels and was increased by increasing the energy input and therefore the mixing time. Copyright © 2010 Society of Chemical Industry     

The effects of extruded black rice flour on rheological and structural properties of wheat-based dough and bread quality

Addition of raw black rice flour leads to deficient processability on bread making quality. One of the effective methods to modify the functional properties of black rice flour (BRF) composite dough is to extrude black rice flour (EBRF) before incorporation. This study investigated and compared the effect of BRF and EBRF addition level of 10%–50% on the rheology, microstructure of dough and bread quality. The rheological properties of composite dough were recorded by Mixolab, stress relaxation and tensile test. The substitution of EBRF presented higher water absorption but lower development time, protein weakening, starch gelatinization, starch gel stability and starch retrogradation than wheat flour dough. Both the BRF and EBRF dough presented solid-like behaviour, while the EBRF dough showed more viscous, higher resistance and extensibility than BRF dough. The dough microstructure of dough was observed by SEM, and a more compact structure of EBRF dough could be seen than BRF dough. The incorporation of EBRF in bread quality presented higher specific volume, lower bake loss and firmness than BRF bread. These findings indicated the potential utilisation value of extruded black rice flour in bread making.     

Functional effects of xanthan gum on composite cassava-wheat dough and bread

The use of composite flour for bread making is gradually gaining prominence worldwide due to some economic and nutritional reasons. However, studies on the application of functional ingredients purposely to improve composite bread quality are very few. This paper examines the functional role of xanthan gum (XG) on the properties of dough and bread from composite cassava-wheat flour. The viscoelastic properties of dough and gas retention characteristics of batter as well as the fresh and storage properties of bread from the composite flour (90% wheat plus 10% cassava) were studied. The crumb cell structure was also studied using digital image analysis technique. Inclusion of XG had significant effects on the dough tenacity and extensibility and sensory acceptability of fresh composite bread. The oven spring, specific volumes of bread loaf and crumb softness were higher at 1% XG content. Also, addition of XG made the composite bread samples had more open crumb structure and better sensory acceptability. However, moisture loss and crumb firming during bread storage were best reduced when 1% XG was added to bread formulation.     

戊聚糖酶与氧化酶对面团流变性质影响的研究

研究了戊聚糖酶(Pentopan)、葡萄糖氧化酶(GOX)以及脂肪氧合酶(活性大豆粉,SF)对普通粉和专用粉面团流变性质的影响。由粉质曲线可知,不同品种的面粉,酶对面团吸水量的影响不同,对普通粉影响最大的是GOX;对专用粉影响最大的是Pentopan。由动态流变学试验知,Pentopan降低了面团中的弹性成分,GOX使弹性成分增加;GOX对普通粉的影响较大,SF则对专用粉的影响较大。     

麦麸粒径对全麦面团流变学特性的影响

麦麸经不同强度超微粉碎后得到4种不同平均粒径(分别为327、209、144、45μm),将麦麸按照出粉率进行回添得到全麦面粉,以探讨不同粒度组成的麦麸对全麦面团流变学特性的影响。糊化特性分析结果显示随着麦麸粒径的逐渐减小,全麦面粉的峰值黏度、最低黏度、最终黏度和回生值等显著增大。粉质特征显示全麦面粉的吸水率随麦麸粒径的减小逐渐增大,但稳定时间减小、弱化度增大。拉伸仪结果表明醒发时间会影响麦麸粒径对面团面筋网络结构的作用,在面筋网络的逐步扩展和形成阶段(45~90、90~135 min),较小粒径的麦麸会促进面筋网络结构变得密实但降低了其延展性。动态流变学特征显示全麦面团的弹性模量和黏性模量随麦麸粒径的减小而减小,但在扫描范围内高于普通面团。由本研究结果可推测,麦麸粒径的减小会促进淀粉颗粒与麦麸层细胞的分离及麦麸纤维在面团中的分布,但增加了面团形成过程中的物理空间阻碍,干扰了蛋白质分子间的交联和面筋网络结构与淀粉颗粒的结合。      

Use of multivariate techniques in studying the flour making properties of some CMD resistant cassava clones

High quality cassava flour (HQCF) is one of the primary products of raw cassava root that has continued to find wider food application in Nigeria. In this study, some 43 newly developed cassava mosaic disease (CMD) resistant clones of cassava were screened based on some physical (flour yield, bulk density, and tri-stimulus colour characteristics (L^∗, a^∗, b^∗, Chroma and Hue)), chemical (moisture, protein, ash, starch, amylose, sugar contents, TTA, pH, and cyanogenic potential), functional (water and oil absorption capacities, water solubility, swelling power, least gelation capacity, diastatic activity, percent damaged starch, and alkaline water retention), and pasting properties. One-way analysis of variance (ANOVA) showed that all properties measured varied significantly (P < 0.001). The flours had a wider range of starch content (65–88%), amylose content (13–23%), water absorption capacity (136–224%), diastatic activity (128–354 mg maltose), peak viscosity (77–328 RVU), final viscosity (56–217 RVU), and trough (32–152). Due to the peculiarity of the experimental data generated, two protocols of applying multivariate statistical techniques were evaluated for discriminating the cassava clones. By first applying principal component analysis (PCA), followed by cluster analysis (CA) and finally, discriminant function analysis (DFA) of the experimental data, it was possible to achieve about 87% correct classification of the cassava clones. The final viscosity and diastatic activity of the flours were found to be the most important variables for classifying the cassava clones.