食品(面团)体系表面胶粘性的流变学机理及其表征

食品（面团）体系表面胶粘性的机理与表征一直是谷物化学和谷物生物技术领域备受关注的前沿科学问题。作者综述了面团体系表面胶粘性的流变学机理和相应的表征方法及影响因素，着重介绍了关于面团表面胶粘性的剥离能理论、压力敏感型胶粘荆（PSA）理论和Hoseney理论，并讨论了其相应的表征方法，包括剥离法、动力机械流变法、表面张力法和探头法。     

Effect of β-Glucan Concentrate on the Water Uptake,Rheological and Textural Properties of Wheat Flour Dough

The effects of the addition of β-glucan concentrate (2.5–10 g/100 g flour) and water (58–70 mL/100 g flour) on the rheological and textural properties of wheat flour doughs were studied. Various empirical (farinograph, extensograph, dough inflation, and dough stickiness) and fundamental rheological tests (oscillatory and creep-recovery) were employed to investigate composite dough structure and an attempt was made to correlate the data obtained from different instrumental measurements. The water absorption increased with the addition of β-glucan concentrate into wheat flour. An increase in mixing time and stability were recorded upon addition of β-glucan concentrate (≤ 5 g/100 g flour), and the extensibility decreased at similar condition. The composite dough exhibited predominating solid-like behavior. The mechanical strength, dough stickiness, the peak dough inflation pressure decreased with increasing water content but those parameters increased with β-glucan concentrate incorporation within the studied concentration range. Creep-recovery tests for 5 g β-glucan concentrate/100 g flour doughs recorded less resistance to deformation with an increase in water level and data were well described by the Burger model. Thermal scanning of doughs revealed that the protein denaturation peak was significantly influenced by water content, and the values were ranged between 110 and 124°C. Significant relationships between empirical and fundamental rheological testing methods were found.     

Effect of Thermal Treatment on Selected Cereals and Millets Flour Doughs and Their Baking Quality

Selected cereals (rice and sorghum) and millets (finger millet and pearl millet) were steamed for 20 min at ambient pressure. The rheological properties of doughs, made from these steamed as well raw grain flours, were characterized in addition to examining their baking quality. The two-cycle compression test was employed and instrumental values were correlated with sensory attributes (color, aroma, taste, stickiness, chewiness, tearing strength, cohesiveness, and rollability) using principal component analysis (PCA). Rice doughs made from both raw as well as thermally treated flour imparted maximum hardness (96.6–99.3 N) and least cohesiveness (0.05–0.09) with highest stickiness values (105–110°) among all the dough samples at the same moisture content. Pearl millet and raw sorghum flour doughs possessed the least instrumental hardness, adhesiveness, and stickiness and were the easiest to flatten. The PCA biplot showed that sensory and instrumental cohesiveness formed a cluster on the left side on the x axis while shear force, and sensory attributes like tearing strength, chewiness, stickiness, and rollability formed another cluster on the other side of the axis. Raw rice and finger millet doughs were associated with the high extent of instrumental and sensory stickiness. Thermally treated pearl millet and sorghum doughs were the best followed by treated rice and finger millet samples to give the desirable dough characteristics, and were quite close to wheat chapathi in texture.     

Physical properties of enzyme-supplemented doughs and relationship with bread quality parameters

The textural properties of wheat doughs made with different commercial amylases, xylanases/pentosanases, lipases and glucose-oxidase, singly and in mixed combinations, were investigated. Parameters from the texture profile analysis (TPA) and measurement of stickiness (Chen and Hoseney test) were determined after mixing the dough and after it had rested for 3.5 h. Resting of doughs led to softer and less cohesive doughs, with higher adhesive properties. Enzymes acted quickly and induced significant changes in the textural properties of doughs immediately after mixing. The influence of enzymes continued during resting. Xylanases/pentosanases substantially reduced dough consistency and increased stickiness, while addition of glucose-oxidase and specific lipases overcame these effects. Strong correlations could be established between different TPA parameters and stickiness and bread quality characteristics (i.e. volume, density and texture). Bread quality could be described by a single or multiple linear combination of textural variables.     

Physical properties of enzyme-supplemented doughs and relationship with bread quality parameters

 The textural properties of wheat doughs made with different commercial amylases, xylanases/pentosanases, lipases and glucose-oxidase, singly and in mixed combinations, were investigated. Parameters from the texture profile analysis (TPA) and measurement of stickiness (Chen and Hoseney test) were determined after mixing the dough and after it had rested for 3.5 h. Resting of doughs led to softer and less cohesive doughs, with higher adhesive properties. Enzymes acted quickly and induced significant changes in the textural properties of doughs immediately after mixing. The influence of enzymes continued during resting. Xylanases/pentosanases substantially reduced dough consistency and increased stickiness, while addition of glucose-oxidase and specific lipases overcame these effects. Strong correlations could be established between different TPA parameters and stickiness and bread quality characteristics (i.e. volume, density and texture). Bread quality could be described by a single or multiple linear combination of textural variables. Received: 21 May 1997 / Revised version: 10 July 1997     

Impact of sourdough, yeast and gluten on small and large deformation rheological profiles of durum wheat bread doughs

The impact of percentage of sourdough (SD) addition and presence of yeast (Y) and/or commercial wheat gluten (G) -added singly and in binary combination- on both small and large deformation rheological performance and viscometric profile of durum wheat bread doughs was considered. Eight distinctive rheological dough features were identified as able/capable to clearly differentiate soured bread doughs made with semolina:remilled semolina rate of 80:20 into defined functional quality groups. The presence of added commercial wheat gluten provided firmer, more elastic and more extensible doughs with slightly lower viscometric profile. Simultaneous presence of yeast/sourdough and yeast/gluten modulate single effects of sourdough on the durum wheat bread dough mechanical properties. Several relationships were found between fundamental and empirical rheological properties and within viscometric features of soured semolina doughs.     

Dynamic rheological properties of dough as affected by amylases from various sources

The effect of alpha-amylases from cereal, fungal, and bacterial sources on dough dynamic rheological properties was investigated. Dynamic rheological study of flour-and-water doughs during resting period showed significant changes in dough rheological properties as a function of alpha-amylases. Addition of alpha-amylases caused a time-dependent decrease in G', storage modulus. The enzyme action on starch during baking increased viscous flow properties. These changes were temperature-dependent. The thermal inactivation temperature of alpha-amylase plays an important role in modification of starch. Rheological changes in dough will alter the machinability of the dough and the quality of end products.     

Origin and practical significance of the sticky dough factor in 1BL/1RS wheats

When translocated into wheat, the short arm of the 1R chromosome of rye carries with it linked resistance genes to powdery mildew, stripe rust, leaf rust and stem rust. The translocation is also reported to increase yield potential of hard wheats. However, many doughs made from some 1BL/1RS hard wheats are unacceptable for breadmaking purposes because of excessive stickiness and mixing intolerance. 1BL/1RS wheats may be sticky because of: the inheritance of secalin proteins from rye and absence of key glutenin subunits; higher amounts and/or differences in the composition of cell wall polysaccharides, β‐glucans and pentosans; and/or the presence of a ferulic acid ester moiety residing with the water‐soluble fraction of 1BL/1RS flours. None of these hypotheses has been proven or disproven, to date, as a cause of excessive stickiness. Investigators have found that 1BL/1RS doughs are not uniformly sticky and are in some instances less sticky than non‐1BL/1RS doughs. Significant genotype–environment interactions have been reported for dough stickiness and flour quality characteristics of 1BL/1RS wheats. Investigators have generally failed to find significant differences in the breadmaking performance of 1BL/1RS and non‐1BL/1RS hard wheats despite a report that 1BL/1RS doughs break down and soften during high‐speed mixing. The 1BL/1RS translocation has been shown to reduce cookie spread of soft wheat flours but has no deleterious effects on cake volume or texture. © 2002 Society of Chemical Industry     

The chemistry of bread making: The role of salt to ensure optimal functionality of its constituents

Large consumptions of dietary sodium have been shown to lead to hypertension, one of the main causative factors in cardiovascular disease. Bread (and other cereal products) accounts for ~30% of the overall sodium intake in our diet; therefore, industry has been developing strategies to significantly reduce its usage. However, at reduced sodium levels, dough handling can be affected due to sticky dough phenomena creating major processing issues and a poor quality final product. It is hypothesized that the formation of a strong gluten network plays a crucial role in developing nonsticky dough, a process that is strengthened in the presence of NaCl. However, at low NaCl levels, a weaker gluten network forms resulting in the prevalence of other wheat flours’ constituents impact on water mobility within the dough to contribute to the stickiness phenomenon. This review discusses the underlying mechanisms that can influence the formation of sticky dough within a low sodium environment and discusses strategies used to help circumvent them.     

Taguchi approach for analyzing the impact of varying degrees of cotton stickiness on ring-spun yarn quality

This research aimed to study the effect of cotton stickiness in quality of ring-spun yarn, the effect of blending sticky with nonsticky cotton, and optimize the spinning process based on Taguchi experiment design technique. Nine experiments were performed with respect to the L9 orthogonal design. Taguchi method was utilized to find the sequence of dominant factors contributing to ring-spun yarn quality. The study showed that a slight and nonsignificant, negative effect on the coefficient of variation in mass of carded sliver, first and second drawn sliver. When considering the roving frame, the coefficient of variation in mass of roving was significantly increased with the increase in the stickiness level and the percentage of sticky cotton in the blends. In actual spinning, the quality of ring-spun yarn is susceptible to stickiness. The study concluded that the dominant factor contributing to the most quality characteristics of ring-spun yarn was cotton stickiness level .The study showed that the optimum condition for the blending ratio of sticky with nonsticky cotton was found to be 25 and 75%, respectively. The results showed a considerable improvement in the signal-to-noise ratio as compared to the initial conditions.     

Extensional flow,viscoelasticity and baking performance of gluten-free zein-starch doughs supplemented with hydrocolloids

Viscoelastic doughs of zein and starch were prepared at 40 °C, above the glass transition temperature of zein. The effects of hydrocolloid supplementation with hydroxypropyl methylcellulose (HPMC) or oat bran with a high content of β-glucan (28%) were investigated by dynamic measurements in shear, confocal laser scanning microscopy (CLSM) and Hyperbolic Contraction Flow. Zein-starch dough without hydrocolloids exhibited rapid age-related stiffening, believed to be caused by cross-links between peptide chains. A prolonged softness was attributed to doughs containing hydrocolloids, with the oat bran exhibiting the most pronounced reduction in age-related stiffening. Moreover, CLSM-images of dough microstructure revealed that a finer fibre network may be formed by increased shearing through an addition of viscosity-increasing hydrocolloids, a reduction in water content in the dough or the use of appropriate mixing equipment. The Hyperbolic Contraction Flow measurements showed that doughs containing hydrocolloids had high extensional viscosities and strain hardening, suggesting appropriate rheological properties for bread making. Zein-starch dough without hydrocolloids showed poor bread making performance while hydrocolloid additions significantly improved bread volume and height. Although the hydrocolloid supplemented doughs had similar extensional rheological properties and microstructures, a fine crumb structure was attributed only to bread containing HPMC, marking the importance of surface active components in the liquid-gas interface of dough bubble walls. Zein could not mimic the properties of gluten on its own, but hydrocolloids did positively affect the structural and rheological properties of zein, which yielded dough similar to wheat dough and bread with increased volume.     

Interactive effects of flour, starter and enzyme on bread dough machinability

 Dough machinability of samples formulated with the enzyme principles glucose-oxidase, lipase, amylase and pentosanase/hemicellulase, and fermented with different microbial starters, was assessed by texture profile analysis and dough stickiness measurements. The individual and interactive effects of flour, enzyme and starter on the primary and secondary mechanical and surface-related parameters were evaluated, and the suitability of enzyme mixtures added to started doughs to improve dough handling characteristics and minimize adhesiveness and stickiness in flours was established. The general improving effect of the mixture of α-amylase, pentosanase and hemicellulase on most dough texture properties is particularly relevant when high-grade and/or sourer-started systems are used, because of their strong effect in decreasing hardness and adhesiveness respectively. Individual additions of glucose-oxidase and lipase cancelled out the excessive stickiness/adhesiveness of started and enzyme-supplemented doughs while the simultaneous presence of glucose-oxidase and lipase improved cohesiveness, chewiness and gumminess. The extent of the effects of this binary combination on dough mechanical characteristics was comparable to that obtained with the ternary mixture of α-amylase, pentosanase and hemicellulase, but avoided the deleterious effect of the latter enzyme combination on stickiness. In well-defined flour-starter systems, the enzyme supplementation of doughs constitutes a useful alternative to chemical improvers for enhancement of dough plasticity. Reveived: 16 February 1998     

Interactive effects of flour, starter and enzyme on bread dough machinability

 Dough machinability of samples formulated with the enzyme principles glucose-oxidase, lipase, amylase and pentosanase/hemicellulase, and fermented with different microbial starters, was assessed by texture profile analysis and dough stickiness measurements. The individual and interactive effects of flour, enzyme and starter on the primary and secondary mechanical and surface-related parameters were evaluated, and the suitability of enzyme mixtures added to started doughs to improve dough handling characteristics and minimize adhesiveness and stickiness in flours was established. The general improving effect of the mixture of α-amylase, pentosanase and hemicellulase on most dough texture properties is particularly relevant when high-grade and/or sourer-started systems are used, because of their strong effect in decreasing hardness and adhesiveness respectively. Individual additions of glucose-oxidase and lipase cancelled out the excessive stickiness/adhesiveness of started and enzyme-supplemented doughs while the simultaneous presence of glucose-oxidase and lipase improved cohesiveness, chewiness and gumminess. The extent of the effects of this binary combination on dough mechanical characteristics was comparable to that obtained with the ternary mixture of α-amylase, pentosanase and hemicellulase, but avoided the deleterious effect of the latter enzyme combination on stickiness. In well-defined flour-starter systems, the enzyme supplementation of doughs constitutes a useful alternative to chemical improvers for enhancement of dough plasticity. Reveived: 16 February 1998     

UNIAXIAL COMPRESSIBILITY OF BLACKGRAM DOUGHS BLENDED WITH CEREAL FLOURS

The uniaxial compression characteristics of papad dough (moisture content 62%, dry basis), made from blackgram flour as well as after incorporation of different types of cereal (rice, sorghum and wheat) flours at different levels (20 and 40%), were determined. The stress-strain data can be interrelated by a power law type equation. The sensory attributes (stickiness, firmness, elasticity and ease of flattening/rolling) were correlated with the energy for compression, deformability modulus and apparent biaxial elongational viscosity. Inelastic doughs resulted from the blackgram dough; doughs with 20% rice or wheat blends were also inelastic but sorghum samples were elastic. The deformability modulus for sorghum doughs were extremely high. The blackgram dough as well as the wheat blended doughs were the easiest doughs to roll/flatten. Blended dough consisting of wheat flour (at 20 and 40% level) or rice flour up to 20% level was suitable for making cereal-blended papad doughs.     

不同磨粉方法对荞麦面团流变学性质的影响

为研究不同磨粉方法对荞麦面团流变学性质的影响,分别采用石磨、高速万能粉碎机及湿磨三种磨粉方法制得荞麦粉。然后测定由上述荞麦粉制备的荞麦面团的热机械学特性、拉伸特性、质构特性及应力松弛行为。结果表明:与干磨荞麦面团相比,湿磨荞麦面团具有显著较低的面团形成时间和稳定时间以及显著较高的蛋白弱化度,但磨粉方法对淀粉糊化特性影响较小。湿磨荞麦面团的拉断距离低于干磨荞麦面团的拉断距离,但其硬度、黏着性、弹性和胶着性显著高于干磨荞麦面团。此外,湿磨荞麦面团与干磨荞麦面团相比具有显著较高的残余应力和显著较短的松弛时间。不同磨粉方法会导致荞麦面团流变学性质产生差异,面团流变学性质的差异将满足不同的加工需求。     

Effect of α-amylases on dough properties during Turkish hearth bread production

Summary The effect of α‐amylases from cereal and fungal sources on dough rheological properties was studied. Increasing the enzyme addition level to 160 SKB units (c. 1.1%, fwb) decreased dough stability and increased mixing tolerance indexes. Gas production rates with cereal α‐amylase were higher than that with fungal α‐amylases, indicating more activity during fermentation. A higher adsorption rate occurred with cereal α‐amylase. Dough stability is very important for Turkish hearth bread production, as it is for other hearth breads. Spread ratio tests on fermented doughs showed significant changes in dough rheological properties as a function of α‐amylases. The spread test is a reliable tool for observing rheological changes during fermentation. As a guide, the dough spread ratio should not be more than 2 for desirable bread.     

Rheological Characterisation of Malaysian Varieties of Sweet Potato Doughs Using Large and Small Deformation Measurements

The rheological properties of sweet potato doughs at different mixing times were studied. In the large deformation extension test, extensibility parameters including dough length at fracture, measured, and actual forces acting on dough strips were obtained for calculating the stress-strain data. For the small deformation test, both storage and loss modulus of dough were studied. The extensibility of dough from sweet potato flour increased to its peak at five minutes mixing time before decreasing illustrating an optimum mixing time. The variety of VitAto which has a higher protein content of 5.7 g/100 g has higher values of all the extensibility parameters as compared to Bukit Naga and Okinawan. In terms of flow-behavior index, all sweet potato doughs displayed n values from 1.82 to 2.11, indicating strain hardening behaviors similar to wheat flour doughs. The small deformation tests were not able to identify the optimum mixing time, although in general, illustrated that sweet potato doughs were essentially elastic or recoverable. The Pearson correlations of large and small deformation tests showed that the rheological parameters were positively correlated among themselves in the evaluation of the effect of mixing time to rheological properties of sweet potato dough.     

Prediction of the rheological properties of wheat dough by starch-gluten model dough systems: effect of gluten fraction and starch variety

The present study sought to investigate the rheological properties of wheat starch-gluten (WS-G) and potato starch-gluten (PS-G) model doughs with different gluten fractions to elucidate the effectiveness of using model dough to predict wheat dough properties. The highest linear viscoelastic region, frequency dependence, maximum creep compliance and the lowest viscoelastic modulus and zero shear viscosity were observed in the wheat dough, followed by WS-G and PS-G model doughs. PS exerted a more significant damage effect on the gluten network while WS shared a tight integration with gluten protein, forming a more stable dough structure. The viscoelasticity of the model doughs shared a close association with the wheat dough under increased gluten fraction, while the frequency dependence of the model doughs showed no trend towards wheat dough. Therefore, starch-gluten model dough could not fully stimulate the functionality of wheat dough irrespective of its gluten fraction.     

THE EFFECT OF HEAT AND SHEAR ON THE VISCOELASTIC PROPERTIES OF SOY FLOUR DOUGH

This paper is concerned with the effect of heat and shear on the rheological properties of defatted soy dispersions and doughs of 30 to 60% flour by weight. Capillary and rotary rheometers (Rheometrics Mechanical Spectrometer) were used to heat doughs up to 75° C and shear them simultaneously. In one series of experiments using a modified Instron capillary rheometer the doughs were heated to several different temperatures and then sheared. The linear viscoelastic properties of the dough which were determined by means of a plate-plate rheometer were then compared to the fresh dough and those of a heated but nonsheared dough. In another experiment a cone-and-plate rheometer was used to heat and shear the dough. The linear viscoelastic response of the dough was used to monitor any changes as it was heated and sheared. It was observed that only in the higher moisture dispersions (i.e., moisture contents greater than 50%) were there any signs of an increase in rheological properties which might be associated with “cooking”. It was concluded that cooking of soy flour doughs most likely does not involve the formation of a permanent network formed by covalent chemical bonds. Hence, in extrusion cooking processes involving soy flour doughs, it may not be necessary to treat the rheological properties of the dough as a thermosetting system.     

Flour Quality effects on percolation of gas bubbles in wheat flour doughs

To investigate how flour affects crumb structures, we used Synchrotron X-ray tomography to scan and capture the growth of gas bubbles in leavened and unleavened bread doughs of two different flours. Bubbles were mobile in all doughs; they coalesced and disproportionated with the rate of coalescence being higher in leavened doughs. In unleavened dough, new bubbles were detected, attributed to arise from poro-visco-elastic relaxation of gluten as dough rested. In each yeasted dough, a single, massively inter-connected cluster formed which percolated at ~26% dough porosity irrespective of flour type in dough. Following percolation, dough expansion was driven primarily by growth of the percolating bubble. Between flours, the rate of coalescence was higher in Wylkatchem (Wylk), an Australian flour dough, than in Canadian Western Red Spring (CWRS) flour dough, known for superior proof and bake qualities. How the physical and rheological properties of dough liquors could have affected the stabilities of bubbles in these doughs have been discussed.