Biaxial Extensional Viscosity Research Articles

Extensional rheometry of mobile fluids. Part II: Comparison between the uniaxial, planar, and biaxial extensional rheology of dilute polymer solutions using numerically optimized stagnation point microfluidic devices

Part I of this paper [Haward et al., J. Rheol. 67, 995–1009 (2023)] presents a three-dimensional microfluidic device (the optimized uniaxial and biaxial extensional rheometer, OUBER) for generating near-homogeneous uniaxial and biaxial elongational flows. Here, in Part II, the OUBER device is employed to examine the uniaxial and biaxial extensional rheology of model dilute polymer solutions, compared with measurements made under planar extension in the optimized-shape cross-slot extensional rheometer [OSCER, Haward et al. Phys. Rev. Lett. 109, 128301 (2012)]. In each case, micro-particle image velocimetry is used to measure the extension rate as a function of the imposed flow conditions, and excess pressure drop measurements enable estimation of the tensile stress difference generated in the fluid via a new analysis based on the macroscopic power balance for flow through each device. Based on this analysis, for the most dilute polymer sample tested, which is “ultradilute”, the extensional viscosity is well described by Peterlin’s finitely extensible nonlinear elastic dumbbell model. In this limit, the biaxial extensional viscosity at high Weissenberg numbers (Wi) is half that of the uniaxial and planar extensional viscosities. At higher polymer concentrations, although the fluids remain dilute, the experimental measurements deviate from the model predictions, which is attributed to the onset of intermolecular interactions as the polymer chains unravel in the extensional flows. Of practical significance (and fundamental interest), elastic instability occurs at a significantly lower Wi in uniaxial extensional flow than in either biaxial or planar extensional flow, thereby limiting the utility of this flow type for extensional viscosity measurement.

Competition between shear and biaxial extensional viscous dissipation in the expansion dynamics of Newtonian and rheo-thinning liquid sheets

When a drop of fluid hits a small solid target of comparable size, it expands radially until reaching a maximum diameter and subsequently recedes. In this work, we show that the expansion process of liquid sheets is controlled by a combination of shear (on the target) and biaxial extensional (in the air) deformations. We propose an approach toward a rational description of the phenomenon for Newtonian and viscoelastic fluids by evaluating the viscous dissipation due to shear and extensional deformations, yielding a prediction of the maximum expansion factor of the sheet as a function of the relevant viscosity. For Newtonian systems, biaxial extensional and shear viscous dissipation are of the same order of magnitude. On the contrary, for thinning solutions of supramolecular polymers, shear dissipation is negligible compared to biaxial extensional dissipation and the biaxial thinning extensional viscosity is the appropriate quantity to describe the maximum expansion of the sheets. Moreover, we show that the rate-dependent biaxial extensional viscosities deduced from drop impact experiments are in good quantitative agreement with previous experimental data and theoretical predictions for various viscoelastic liquids.

Biaxial extensional viscous dissipation in sheets expansion formed by impact of drops of Newtonian and non-Newtonian fluids

We investigate freely expanding liquid sheets made of either simple Newtonian fluids or solutions of high molecular water-soluble polymer chains. A sheet is produced by the impact of a drop on a quartz plate covered with a thin layer of liquid nitrogen that suppresses shear viscous dissipation thanks to an inverse Leidenfrost effect. The sheet expands radially until reaching a maximum diameter and subsequently recedes. Experiments indicate the presence of two expansion regimes: the capillary regime, where the maximum expansion is controlled by surface tension forces and does not depend on the viscosity, and the viscous regime, where the expansion is reduced with increasing viscosity. In the viscous regime, the sheet expansion for polymeric samples is strongly enhanced as compared to that of Newtonian samples with comparable zero-shear viscosity. We show that data for Newtonian and non-Newtonian fluids collapse on a unique master curve where the maximum expansion factor is plotted against the relevant effective \textit{biaxial extensional} Ohnesorge number that depends on fluid density, surface tension and the biaxial extensional viscosity. For Newtonian fluids, this biaxial extensional viscosity is six times the shear viscosity. By contrast, for the non-Newtonian fluids, a characteristic \textit{Weissenberg number}-dependent biaxial extensional viscosity is identified, which is in quantitative agreement with experimental and theoretical results reported in the literature for biaxial extensional flows of polymeric liquids.

Effects of fermentation on the rheological characteristics of dough and the quality of steamed bread

During the production of steamed bread, fermentation is a critical step to obtain a final product with the desired characteristics. The quality of the final steamed bread is significantly affected by the properties of the dough. This study investigated the effects of fermentation on the rheological properties, state of water, microstructure of the dough, and the quality of steamed bread. After fermentation, the steamed bread dough exhibited higher stickiness, and was more easily to break during uniaxial extension. Biaxial extension tests revealed a significant decrease in biaxial extensional viscosity from 110,118 (0 min) to 11,544 Pa·S (80 min) at the strain rate of 0.04/S. The properties of the dough matrix were closely related to the fermentation time and the quality of the steamed bread is significant affected by the fermentation time. The results is valuable to provide theoretical basis for steamed bread making under precise control. Practical applications Fermentation is a key step in the production of steamed bread. This study (a) investigated the rheological properties of Chinese steamed bread dough during fermentation, including dough stickiness, uniaxial extensibility, and biaxial extension; (b) evaluated the effects of fermentation on the microstructure of fermented dough and steamed bread quality; and (c) investigated the relationship between the fermentation process and the quality of steamed bread. The information provided in this work will serve as the basis for further study on physical properties of fermented dough. The results is very valuable to provide theoretical basis for determining quality during the industrial production of steamed bread. This potentially leads to improved quality of steamed bread under precise control.

Biaxial extensional viscosity in wheat flour dough during baking

Lubricated squeezing flow (LSF) experiments on wheat flour dough were conducted at a constant biaxial extensional rate followed by relaxation experiments. The effect of temperature on the rheology of the dough was studied in the range 25–95 °C under small and large strain to characterize changes in the dough through a possible pathway to simulate the dough-crumb transition during the first step of the baking process. A strain hardening effect was shown over the whole temperature range. Like extensional viscosity measured at 0.1 and 0.65 biaxial strain, the consistency index (K) decreased from 25 °C to 45 °C and increased at temperatures above 50 °C. Two levels of the behaviour index (n) were found: 0.35–0.40 below 45 °C, and 0.1–0.2 above 45 °C. The relaxation degree also changed dramatically but only at higher temperatures (56–60 °C), below which it remained almost constant (98-99%), once the dough became a viscoelastic liquid, above this temperature the main physical-chemical reactions (starch and protein) started to occur, leading to more solid properties. These results complement those of LSF. LSF experiments at large biaxial strain (0.75), combined with a relaxation experiment, were successfully used for dough/crumb characterisation at a temperatures ranging from 25 °C to 74 °C. Alpha values estimated from Launay's model were incorporated in the flow behaviour index, underwent the same type of changes as a function of temperature as n but with a less marked transition; n was divided by two and K increased by about one decade.

Green Banana (Musa cavendishii) Osmotic Dehydration by Non-Caloric Solutions: Modeling, Physical-Chemical Properties, Color, and Texture

Osmotic dehydration effects on the kinetics and on some quality attributes of green banana slices (Musa cavendishii) at 25 °C with non-caloric solutes (glycerol, sorbitol, and a mixture of both) at concentrations varying from 40 to 60 g/100 g for up to 6 h were studied. The three-component diagram showed that the first pseudo-equilibrium was achieved, and the water pseudo-diffusion coefficient presented higher values with glycerol solutions. A modified Peleg’s model was applied to obtain the maximum water loss. Changes in green banana physical-chemical properties were observed: moisture content from 1.25 to 0.19 kg/kg dry basis, soluble solute content from 5.4 to 16.9 °Brix; total color-difference from 2.7 to 15.8; and the maximum biaxial extensional viscosity from 0.63 to 1.53 MPa s. Moreover, the obtained low chroma difference values suggest that the osmotically drying process may be a suitable technique to preserve the final color of green banana slices.

Frozen baguette bread dough I. Rheological behavior during storage

The present study aimed to evaluate the effect of frozen dough storage period on the rheological behavior of baguette bread doughs. A uniaxial compression rheological technique was used to measure strain hardening index (SHI) of the doughs and use as a prediction of the bread baking quality. Three types of flours were used to prepare the bread doughs, and the doughs were stored frozen (−18 °C) up to 45 days. All flour doughs at different frozen storage period showed shear thinning behavior, since extensional viscosity decreased with increasing strain rate, after sharp initial rise. The biaxial extensional viscosity decreased with increased frozen storage period, irrespective of flour type. The results also showed similar trends for SHI values. The SHI ranged from 1 to 2, and the doughs with weaker gluten strength possessed the lower SHI values. The flour with the lowest protein content, wet gluten and sedimentation values, produced dough with the lowest SHI values, irrespective of frozen dough storage period. The results of this study revealed that the SHI has a promising potential to be used for assessing the quality of frozen dough during storage, even for flour samples having similar protein content and strength.

Role of Starch in Biaxial Extensional Viscosity of Flour Dough

Biaxial extensional viscosity of the doughs prepared from gluten and wheat starch at six ratios and from gluten and starch of different sources at a fixed ratio was determined in this work. The doughs containing more starch have lower viscosity. Increasing starch from 60% to 80% gives a marked increase in viscosity. The viscosity of the doughs containing foxtail millet starch and potato starch is much higher than that of the doughs containing corn and wheat starches. Both amount and type of starch are important for the biaxial extensional viscosity of dough, while the size of starch is not a vital factor.

Rheological properties of wheat dough supplemented with functional by-products of food processing: Brewer’s spent grain and apple pomace

The physicochemical properties of brewer’s spent grain (BSG) and apple pomace (AP), and their effect on dough rheological properties were investigated. BSG had high protein content and both by-products were found to be high in dietary fibre. The rheological and the pasting properties of dough were significantly altered by the addition of by-products, with the main effects being due to the presence of dietary fibre. The biaxial extensional viscosity was significantly higher for the supplemented doughs; the strain hardening index decreased with increasing the levels of flour substitution. The replacement of wheat flour with the by-products significantly reduced the uniaxial extensibility, while the storage modulus, G″, was found to increase, indicating changes in the structural properties of dough. These changes were reflected in the ability of dough to rise during proofing.

Brama australis gel obtention and rheological characterization

Gelatine from marine sources has been looked upon as a possible alternative to bovine and porcine gelatine. Common problems connected with fish gelatine from cold water species, such as those from Chilean coast, are low gelling and melting temperature and low gel modulus. Squeezing flow technique was applied to obtain rheological parameters as function of moisture content, temperature dependence of extensional viscosity, etc. This work studied effects of pH and concentration on the extensional viscosity of brama australis fish gelatine gels using lubricated squeezing flow method and obtained that biaxial extensional viscosity increases with increasing Brama australis fish gelatine concentration.

Dough characteristics of Irish wheat varieties I. Rheological properties and prediction of baking volume

Eight wheat varieties suitable for cultivation in Ireland were examined for the rheological properties and baking quality. Large deformation extensional rheology was used employing the Extensograph, the Kieffer extensibility rig, the Alveograph and biaxial extension by uniaxial compression. Similar discrimination between the wheat samples was achieved with both uniaxial extension methods used. Stress during uniaxial extension was higher at all strains measured than biaxial extension and the difference between uniaxial and biaxial stress increased with increasing strain. Also, differences existed in the strain hardening index between uniaxial and biaxial extension which depended on the sample tested. Significant correlations were established between loaf volume and the rheological properties determined in both uniaxial and biaxial extension. It was found that high loaf volumes can be achieved when biaxial and uniaxial extensibility is high and biaxial extensional viscosity is low. The importance of considering the standard error for validating the value of the correlation for prediction purposes was also demonstrated. When the standard error of the correlation was considered, the value of the correlation for prediction purposes was limited in practice. Nevertheless, the rheological tests provided useful information, and the results were valuable for screening flours for baking quality.

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

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. 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. 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.

Rheological properties and baking quality of wheat varieties from various geographical regions

Eight wheat varieties, originating from various geographical regions were examined for their rheological properties during large uniaxial and biaxial extensions and for their baking quality. Extensibility during uniaxial extension as well as biaxial extensional viscosity proved to be significant properties in predicting loaf volume. Multiple regression analysis indicated uniaxial extensibility and biaxial extensional viscosity as best predictors for loaf volume. The varieties with the highest strain hardening index were those of high loaf volume and also fine and soft crumb, whereas varieties of low strain hardening index were of poor baking quality. However, baking behaviour was not completely explained by considering only the strain hardening index. Crumb fineness was also investigated and it was taken into consideration when evaluating the varieties for their baking quality. 3D scatter plots of loaf volume, cell volume, and number of cells in the slice, divided the wheat samples in groups depending on their baking quality and common rheological characteristics were observed for these groups. The samples were also examined for their proofing capacity. Maximum dough height from the rheofermentometer correlated with loaf volume and was affected by rheological properties of the samples.

MEASURING RHEOLOGICAL CHARACTERISTICS AND SPREADABILITY OF SOFT FOODS USING A MODIFIED SQUEEZE‐FLOW APPARATUS

ABSTRACT The rheological characteristics of soft foods such as peanut butter, mayonnaise and margarine were evaluated by the UW Meltmeter, a modified squeezing‐flow device, applying a constant load under constant volume and changing area. Sample thickness profiles were measured as a function of time and the yield stress was calculated via a Herschel–Bulkley model as a measure of spreadability. Peanut butter exhibited the highest yield stress value (1.31–1.45 kPa) followed by margarine (0.80 kPa) and mayonnaise (0.31 kPa). Calculated values of biaxial extensional viscosity and consistency coefficient values calculated from the UW Meltmeter data followed the expected trends of relative spreadability of peanut butter, margarine, and mayonnaise. These results show that the UW Meltmeter is a relatively simple and reliable device for measuring yield stress and rheological properties of soft foods. PRACTICAL APPLICATIONSA new method has been proposed to measure yield stress of spreadable foods.

Biaxial Extensional Viscosity of Sheeted Noodle Dough

ABSTRACTThe 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 (ηBmax) 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.

A comparison of the ability of several small and large deformation rheological measurements of wheat dough to predict baking behaviour

The rheological characteristics of twenty wheat flour samples obtained from four organic flour blends and a non-organic control were compared in relation to their ability to predict subsequent loaf volume in the baked bread. The flour samples considered had protein contents that varied between 11–14 g/100 g. Four different rheological methods were employed. Oscillatory stress rheometry on the protein gel extracted from the wheat flour, oscillatory stress rheometry and creep measurement on undeveloped dough samples and biaxial extensional measurements on simple flour–water doughs. None of the fundamental rheological parameters correlated with loaf volume. There was a correlation between the storage modulus of the gel protein and storage modulus for the undeveloped dough ( r = 0.85). There was a weak negative correlation between protein content and biaxial extensional viscosity ( r = −0.62). Stepwise multiple regression related loaf volume to dough stability time (measured on the Farinograph) and tan (phase angle) for the undeveloped dough samples (overall model r 2 = 0.54). The results indicate that the four rheological tests considered could not be used as predictors of subsequent loaf volume when the bread is baked.

Mechanism of Polymer Drag Reduction Using a Low-Dimensional Model

Using a retarded-motion expansion to describe the polymer stress, we derive a low-dimensional model to understand the effects of polymer elasticity on the self-sustaining process that maintains the coherent wavy streamwise vortical structures underlying wall-bounded turbulence. Our analysis shows that at small Weissenberg numbers, Wi, elasticity enhances the coherent structures. At higher Wi, however, polymer stresses suppress the streamwise vortices (rolls) by calming down the instability of the streaks that regenerates the rolls. We show that this behavior can be attributed to the nonmonotonic dependence of the biaxial extensional viscosity on Wi, and identify it as the key rheological property controlling drag reduction.

Rheological characteristics of wheat flour dough as influenced by ingredients of parotta

The effects of addition of salt (0.5%, 1.0% and 1.5%), sugar (0.5%, 1.0% and 1.5%), egg (2.5%, 5.0% and 7.5%) and refined groundnut oil (5.0%, 10.0%, 15.0% and 20.0%) on various rheological characteristics of dough, as measured by the farinograph, mixograph, extensograph and Instron universal testing machine, were studied. Addition of increasing amounts of salt, egg and oil increased farinograph stability from 3.5 min for the control sample to 9.5, 4.5 and 6.5 min, respectively and decreased to 3.0 min with sugar. The extensograph ratio figure, area increased with the addition of egg and decreased on addition of oil. The mixograph peak height increased when salt or egg was added, but decreased on addition of oil and addition of sugar produced no effect. Values of apparent biaxial extensional viscosity (ABEV), compressive stress, hardness and cohesiveness increased on addition of salt or egg, but they decreased on addition of sugar or oil. The force decay parameter value decreased with the addition of salt and egg, but increased when sugar or oil was added. The adhesiveness value decreased when salt or egg or oil was added, but increased with sugar; indicating thereby addition of salt or egg produces an increase in the strength and elasticity of the dough, on the other hand, addition of oil decreases the strength and viscosity of the dough.

EFFECT OF ADDITIVES ON RHEOLOGICAL CHARACTERISTICS AND QUALITY OF WHEAT FLOUR PAROTTA

ABSTRACT Effects of oxidizing agents (potassium bromate [20 and 40 ppm], ascorbic acid [100 and 200 ppm] and potassium iodate [20 and 40 ppm]), reducing agents (potassium metabisulphite [100 and 200 ppm] and cysteine hydrochloride [50 and 100 ppm]), enzymes (fungalα‐amylase [10 and 20 ppm] and protease [10 and 20 ppm]) and dry gluten powder (1, 2 and 3%) on rheological characteristics of dough and quality of parotta were studied. Addition of oxidizing agents and dry glutenincreased values for farinograph stability, extensograph and mixograph areas, apparent biaxial extensional viscosity, compressive stress, hardness and cohesiveness, while reducing agents and enzymes decreased the aforementioned characteristics and increased force decay parameter and adhesiveness of the dough. Among the different additives studied, incorporation of 100‐ppm potassium metabisulphite, 50‐ppm cysteine hydrochloride and 10‐ppm protease increased the overall quality score of parotta.

Nucleation and Expansion During Extrusion and Microwave Heating of Cereal Foods.

Expansion of biopolymer matrices is the basis for the production of a wide variety of cereal foods. A limited number of manufacturing processes provide practical solutions for the development of an impressive variety of expanded products, just by changing process variables. It is therefore essential that the mechanisms involved in expansion are well known and controlled. This paper summarizes the knowledge of nucleation and expansion in extruded and microwaved products available to date. The effect of processing conditions and properties of the biopolymeric matrix on nucleation and expansion are discussed. Moisture content enables the glassy polymeric matrix to turn into rubbery state at process temperatures, which allows superheated steam bubbles to form at nuclei and then expand, expansion being governed by the biaxial extensional viscosity of the matrix. Nucleation and expansion theories are presented along with quantitative data that support them.