Recovery Compliance Research Articles

Rheological and Textural Properties of Short (Cookie) Dough Made with Two Types of Resistant Starch

AbstractThe influence of two types of resistant starch, type 3 (RS3) and type 4 (RS4), on the rheological and textural properties of short (cookie) dough was studied. RS3 or RS4 were added in dough as a replacement of flour in concentrations of 0, 5, 10 and 15%.In all dough samples, the use of RS resulted in the increase of elastic and viscous moduli and the lowering of loss tangent, which indicates that it is characteristically more elastic (because of the ability of RS to bind water). Generally, the incorporation of the RSs reduced creep and recovery compliance and elevated zero shear viscosity. Samples with the RS3 and RS4 addition had a less destructive structure and a greater ability for recovery.Control sample had significantly lower extensibility and resistance to extension than all samples containing the RSs. The increasing proportion of both RS ingredients in the formulation produced softer doughs.Practical ApplicationsResistant starch (RS) is included in the definition of dietary fiber and demonstrates similar physiological benefits as dietary fiber. RS has better taste, color and aroma than “conventional” fibers. The application of RS in cookie formulations can improve nutritional quality of cookies by increasing the fiber content and reducing the energy value. The present results demonstrated that both RS ingredients have good potential for developing fiber‐rich cookies and similar products.

Detecting very low levels of long-chain branching in metallocene-catalyzed polyethylenes

The detection of long-chain branches (LCBs) is an issue of significant importance in both basic research and industrial applications, as LCBs provide excellent means to improve the processing behavior, especially in elongation-dominated processing operations. In this article, different methods for the detection of very low amounts of LCBs in metallocene-catalyzed polyethylene are presented and compared with respect to their sensitivity. Depending on the molar mass, the zero shear rate viscosity increase factor η 0/ $\eta_{0}^{\rm lin}$ , the steady-state elastic recovery compliance $J_{e}^{0}$ , the complex modulus functions G′(ω) and G″(ω), and the thermorheological complexity were found to be sensitive. In general, the higher the molar mass, the more important the transient quantities become and the easier finding the long-chain branches gets. Although rheology is very sensitive, rheological methods in combination with size exclusion chromatography proved to be the most sensitive combination to detect even very low amounts of LCBs. Especially methods involving the elastic properties (G′(ω), $J_{\rm e}^{0}$ , and J r(t)) react very sensitively, but these are also very distinctly influenced by the molar mass distribution.

Non-linear creep-recovery measurements as a tool for evaluating the viscoelastic properties of wheat flour dough

Creep-recovery measurements were used to analyze the non-linear viscoelastic properties of wheat flour. First the effect of creep time, recovery time and shear stress was investigated on the non-linear viscoelastic properties of Bussard dough. The Burgers model was fitted to the creep and recovery curves. A linear increase of maximum creep compliance was observed with increasing creep time. On the other hand, maximum recovery compliance remained constant but an increase of the retardation time was observed which indicates a slower recovery. A recovery time of 10min seemed to be sufficient to obtain most of the recovery. Maximum creep compliance increased proportionally with increasing shear stress until a plateau was reached. Maximum recovery was constant between 100 and 500Pa but the speed of the recovery increased as shear stress increased. Finally, the optimised creep-recovery methodology was used to analyze the non-linear viscoelastic properties of 17 pure wheat cultivars. By applying principal component analysis, it was possible to identify three groups of wheat cultivars with similar rheological properties and bread volumes.

Evidence of intra-chain phase separation in molten short-chain branched polyethylene

Intramolecular phase separation is usually associated with block-copolymers, but the same phenomenon is also obtainable by random-copolymers. In this article, evidence of intramolecular phase separation is reported for a linear octadecene-ethene copolymer, which shows an evolving 'yield point' at a long time and low frequency. This is attributed to a partial phase separation of the long short-chain branches. In creep recovery, this behavior is evident as increasing elastic steady-state creep recovery compliance Je 0 . In contrast to 'normal' block-copolymers, this special polymer has an increase in phase separation with temperature, which is caused by the chemical composition and the short chain segments in the side chain domain, leading to a high surface fraction.

Separating stress and time dependent effects in the temperature dependent creep of polyethylene nanocomposites

AbstractThe nonlinear time dependent creep of linear‐low density polyethylene (LLDPE) reinforced with montmorillonite layered silicate was investigated. A previous study related the time/stress dependence of creep compliance of the material at room temperature using the Burger and Kohlrausch‐Williams‐Watts models. Using both the creep and recovery compliance curves, we employ the Schapery formulation to study the relationship between deformation, time, stress, and temperature of LLDPE nanocomposites. Smooth mastercurves are constructed using time–temperature–stress superposition principles. The stress and temperature‐related creep constants and shift factors were determined for the material using the Schapery nonlinear viscoelastic equation. The prediction results confirm the enhanced creep resistance of nanofillers even at extended time scales and low temperatures. POLYM. ENG. SCI., 50:1646–1657, 2010. © 2010 Society of Plastics Engineers

The impact of resistant starch on characteristics of gluten-free dough and bread

The study focused on partial replacement in gluten-free breads of corn starch with tapioca and corn resistant starch preparations. The use of resistant starch resulted in the increase of storage and loss moduli of the dough, and the lowering of loss tangent, which indicates its more elastic character. The incorporation of resistant starch reduced creep and recovery compliance and elevated zero shear viscosity. Modified doughs displayed higher starch gelatinization temperatures and lower viscosities that were proportional to the share of RS. It was found that the loaves baked with the share of resistant starch had less hard crumb than bread without RS addition. The crumb hardness diminished with the increasing amount of applied RS preparation. The addition of resistant starch raised total dietary fibre, by up to 89%, as compared to control (bread without RS addition). The most pronounced change was observed for insoluble dietary fibre (increase 137%), while only slight increase was found for its soluble fraction (18%).

Effect of Ca and P Content, Residual Lactose, and Salt-to-Moisture Ratio on the Model Parameters of Process Cheese Linear Viscoelastic Properties

The main aim of this study was to investigate the influence of two different levels (high and low) of Ca and P (calcium and phosphorous) content, residual lactose, and salt-to-moisture (S/M) ratio on viscoelastic properties of eight different process cheeses. Frequency sweep was performed at 750 Pa on all experimental process cheese samples to determine the power-law model parameters. Process cheeses with high Ca and P content and high S/M ratio were significantly harder (P < 0.05) (higher storage and loss modulus, and lower creep and recovery compliance) compared to low Ca and P content and low S/M ratio process cheeses. However, no significant difference was observed (P > 0.05) for power-law parameters between high/low residual lactose content process cheese samples. Six-element Kelvin-Voigt model was used to predict the creep compliances for eight different process cheeses. This model described the affect of above treatment's retardation spectra (compliances, viscosities, and retardation times) obtained from creep tests. Both of these measurements indicated the similar trend on linear viscoelastic properties for eight different process cheeses.

Influence of Starch and Gluten Characteristics on Rheological Properties of Wheat Flour Gel at Small and Large Deformation

ABSTRACTStarch and gluten were isolated from 10 wheat cultivars or lines with varied amylose content. The rheological properties of 30% wheat flour gel, starch gel, and the gel of isolated gluten mixed with common starch were determined in dynamic mechanical testing under shear deformation, creep‐recovery, and compression tests under uniaxial compression. Variation of wheat samples measured as storage shear modulus (G′), loss shear modulus (G″), and loss tangent (tan δ = G″/G′) was similar between flour and starch gels and correlated significantly between flour and starch gel. The proportion of acetic acid soluble glutenin exhibited a significant relationship with tan δ of gluten‐starch mixture gel. The small difference in amylose content strongly affected the rheological parameters of flour gels in creep‐recovery measurement. Wheat flour gel with lower amylose content showed higher creep and recovery compliance that corresponded to the trend in starch gel. Compressive force of flour gel at 50 and 95% strain correlated significantly with that of starch gel. Gel mixed with the isolated gluten from waxy wheat lines appeared to have a weaker gel structure in dynamic viscoelasticity, creep‐recovery, and compression tests. Starch properties of were primarily responsible for rheological changes in wheat flour gel.

Terminal viscous and elastic properties of linear ethene∕α-olefin copolymers

Several linear ethene∕α-olefin copolymers with butene, hexene, octene, dodecene, octadecene, and hexacosene as comonomers were characterized in linear-viscoelastic shear flow. Creep and creep recovery measurements were used to obtain the zero shear-rate viscosity η0 and the steady-state elastic recovery compliance Je0. The correlation between the zero shear-rate viscosity and the weight average molar mass η0(Mw) established for metallocene catalyzed high density polyethylene (mHDPE) was found to be obeyed by all samples containing comonomer contents up to 29wt%. For the linear steady-state elastic compliance Je0 an increase with growing molar mass Mw or comonomer content wc was observed.

Anelastic strain recovery compliance of rocks and its application to in situ stress measurement

Laboratory experiments were performed under uniaxial compression for seven rocks, to measure anelastic strain recovery (ASR) compliance in volumetric and shear modes. Together with previous experiments in uniaxial, hydrostatic and triaxial compression, the effects of both the rock type and the magnitude of stress on ASR compliance in both modes were analyzed, with particular focus on long-term ASR compliances resulting in ultimate values of J aV2f and J aS2f in volumetric and shear modes, respectively. The results showed that the values of J aV2f and J aS2f obtained in uniaxial compression at 50% of the uniaxial compressive strength can be approximately determined by the tangential Young's modulus at 50% of the uniaxial compressive strength ( E 50). The ratio J aV2f/ J aS2f obtained in uniaxial compression at 50% of the uniaxial compressive strength converges within a narrow range at a sufficient elapsed time for all of the rocks used in this study, whereas the long-term ASR compliances in both modes are not a similar function of time. The ratio J aV2f/ J aS2f significantly decreases with the mean normal stress since J aV2f decreases and J aS2f increases as the mean normal stress increases. Thus, a method is suggested for determining the approximate magnitudes of principal stresses without referring to ASR compliance but rather by considering the effect of the mean normal stress on long-term ASR compliance. This method was verified by applying it to experimental data. Furthermore, a method is proposed for determining the applicability of the ASR method prior to its application in the field by using the depth and the value of E 50.

Determination of three-dimensional in situ stresses from anelastic strain recovery measurement of cores at great depth

In order to examine whether the anelastic strain recovery (ASR) method can be applied for determining the in situ stress in hard rocks at great depths, the anelastic strain recovery of oriented cores was measured in six independent directions. The core specimens were taken from four depths within the range of about 2400–4500 m MD at the METI Niitsu well in Japan; the rock materials were mudstone, dolerite, basalt and andesite. For all the rocks the expansional anelastic strains were obtained, the magnitude of the strains in various directions continuously measured for 1 or 2 weeks was of the order of 1000 × 10 − 6 in mudstone; in contrast, strains of the other cores did not exceed a few hundred microstrains. These strains were used for a three-dimensional analysis of the principal in situ stresses. At the third depth, the principal stress directions were considered to be affected by fractures pre-existing near the core, and showed the features of a very local stress state. With the exception of this data, the directions determined by the ASR method were in agreement with those determined using other in situ measurement methods. Based on two assumptions, i.e., (i) the rock stress in vertical direction is equal to density-related gravitational overburden stress, (ii) the ratio of anelastic strain recovery compliance of shear deformation mode and the compliance of volumetric deformation mode is equal to 2, the values of the three principal stresses were estimated. The values of the minimum principal stress in the plane perpendicular to the well axis determined in this study were in agreement with those determined based on extended leak-off tests (ELOT or XLOT) conducted at the same well. Therefore, it can be said that the ASR method is well suited for use in directly determining the directions of principal in situ stresses in three dimensions and in estimating the magnitude of the stresses in isotropic rocks at great depths, such as those encountered when drilling deep into a submarine seismogenic zone.

Introduction of long-chain branches in linear polyethylene by light cross-linking with 1,3-benzenedisulfonyl azide

Metallocene synthesised HDPE with M w=82,000 and M n=40,000 was modified with small amounts of 1,3-benzenedisulfonyl azide by reactive extrusion at 200 °C with the purpose to form long-chain branches. At the processing temperature the two azide groups decompose to nitrenes that work as cross-linkers for PE. Cross-linking occurs primarily by insertion of singlet nitrenes into CH bonds. Size exclusion chromatography revealed that the modification resulted in the formation of a long-chain branched (LCB) high molecular weight fraction. The LCB was detectable with SEC for concentrations above 100 ppm corresponding to approximately 0.03–0.04 branch points pr 10 4 carbon. No signs of the formation of low molecular species due to chain scission were observed. Dynamical mechanical analysis and shear creep test showed sign of long chain branching at concentrations down to the same limit as SEC (100 ppm). These signs were thermorheological complexity, increased zero shear viscosity, increased shear thinning and increased recovery compliance. The cross-linking efficiency of 1,3-BDSA were estimated to 40–60% from comparison of SEC data with random cross-linking theory and traditional SEC-LCB analyses.

A practical way to manage IT costs

AbstractInformation technology (IT) consumes 4 percent of a typical large company's revenue. And these days, companies are under tremendous pressure to manage IT costs—while also handling new concerns about disaster recovery, security, and regulatory compliance. That's tough, concedes the author of this article. But he offers a tested, practical strategy to get the job done. © 2005 Wiley Periodicals, Inc.

Rheological Properties of White Salted Noodles with Different Amylose Content at Small and Large Deformation

ABSTRACTThe rheological properties of cooked white salted noodles made from eight wheat cultivars with varied amylose content were analyzed at small and large deformation. Their dynamic shear viscoelasticity was measured using a rheometer with parallel plate geometry. Compressive force and creep‐recovery curves were measured using various probes and sample shapes. Noodles with lower amylose content showed a lower storage shear modulus (G′) and a higher frequency dependence of G′. The G′ values of noodles were highly correlated with amylose content in wheat flour and with G′ values of 30 and 40% starch gels. Remarkable differences in the characteristics of creep‐recovery curves were observed between cultivars. The difference in amylose content in wheat flour reflected the creep‐recovery properties of noodles. A negative correlation was demonstrated between amylose content and both maximum creep and recovery compliance. The compressive force required for 20, 50, 80, and 95% strains was compared. At 20 and 50% strain, noodles made from lower amylose wheat flour showed lower compressive force. Noodles of waxy wheat had a higher compressive force than nonwaxy noodles when the strain was &gt;80%, indicating the waxy wheat noodles are soft but difficult to completely cut through.

EFFECT OF METHOCEL AS A WATER BINDER ON THE LINEAR VISCOELASTIC PROPERTIES OF MOZZARELLA CHEESE DURING EARLY STAGES OF MATURATION

Changes in the dynamic and transient rheological character of highmoisture, skim milk (HMSM) Mozzarella cheese due to the addition of 0.2% Methocel (methyl cellulose) as a water binder at room (25C) and refrigeration (7C) temperatures during early stages of maturation (1, 5, 7, and 14 days after manufacture) were investigated. The HMSM Mozzarella with 0.2% Methocel was softer (lower dynamic storage and loss modulus, and higher creep and recovery compliance) compared to HMSM Mozzarella without Methocel, due to improved water holding capacity. The age‐dependent frequency dispersions of dynamic mechanical spectra (storage and loss modulus) were fitted to a power‐law model. A six‐element Voigt‐Kelvin mechanistic model described the age‐dependent retardation spectra (compliances, viscosities, and retardation times) obtained from creep experiments. Strong correlation was obtained between the viscoelastic

Recent developments in binder design for advanced media

This study is aimed to examine the technical issue, the rheological requirements, in accomplishing successful processing of the dispersion made with wetting binders to produce tapes with excellent mechanical properties. The results indicate that the dispersions made with DTPU or NTPU (new dispersing TPU for metal pigments), can be characterized using RFS 8400 and Bolin CSM. For this type of dispersion, a higher strain is required to start flow or to break the primary structure, a wider range of shear rate is needed for the structural breakdown. It also shows that the recovery time is shorter with longer time to reach a steady state that is a lower recovery compliance level. G′/ G″ cross-over point was defining the needed strain level and the strain rate for the structural breakdown. It is expected that the results of the study could be applied to define the mechanical properties of the final tape affected by various operations such as mixing/agitation, high coating speed, drying/calendering, and curing and high speed duplicating process.

ＡＳＲ法による岩手県湯ノ森地域の三次元地圧計測

The ASR (Anelastic Strain Recovery) method for measuring three-dimensional in-situ stresses, which had been developed by one of the authors, was successfully applied at Yunomori geothermal field, Japan for seven cores collected from the depths of up to about 1, 500m of two wells. The rocks were tuffs, a shale and an andesite. Temperatures of the cores were from 100 to 210°Cbefore drilling. From the data of anelastic normal strains measured with strain gauges in six independent directions, both principal stress directions and the ratios of principal stress deviations were determined without knowing the anelastic strain recovery characteristics of the rocks. The results were consistent with the orientation of the maximum principal stress estimated from borehole breakouts observed in the wells and also consistent with the direction of the maximum horizontal compression observed by surface survey. Furthermore, for one of the cores, magnitudes of principal stresses were determined by calibrating the anelastic strain recovery compliances of both shear and volumetric modes in the laboratory under the conditions of drained triaxial compression. The results were compared with those obtained by DSCA and the combined AE and DRA methods carried out by NEDO. The results of the ASR method were consistent with those of DSCA.

岩石の非弾性ひずみ回復を用いた三次元地圧計測法の理論的検討

Anelastic strain recovery method is one of inexpensive and simpler methods for measuring in-situ stresses at great depth. However, the method has been based on the critical assumptions that the vertical boring axis is one of principal directions and that vertical stress is given by overburden pressure, which are not always true for actual rock masses.In this study, by deriving a fundamental equation on the anelastic strain recovery of isotropic visco-elastic material in general three dimensional stress state, the method for measuring three-dimensional in-situ stresses has been proposed. In the method, by measuring six independent anelastic normal strains of a core, six anelastic strain deviations and anelastic volumetric strain are determined first. From the former, the orientations of principal in-situ stresses and ratios of principal in-situ stress deviations are determined without the knowledge of anelastic strain recovery compliances of the core, in-situ pore pressure and temperature change in the core. Then, by evaluating pore pressure and by correcting the effect of temperature change on the anelastic volumetric strain, absolute three dimensional in-situ stresses are determined by measuring the anelastic strain recovery compliances of the rock core in both shear and volumetric modes in the laboratory.

Tensile creep modulus, creep lateral contraction ratio and torsional creep measurements on small nonrigid specimens

A torsional creep apparatus incorporating a novel linear bearing to permit simultaneous application of axial and torsional creep stresses to small nonrigid specimens is described. The results of a detailed examination of the capabilities of this apparatus and a comparison of shear creep and recovery compliance data is made (as measured direct in torsion and calculated from the axial and lateral strain data in tension). The measurements were made on isotropic and oriented sheets of low-density polyethylene and the use of oriented, as well as the more usual isotropic, material in such trials is illustrated.

木材のレオロジーに関する研究 (第6報)

It is well known that the mechanical properties of wood are very much affected by temperature and by relative humidity. In the light of the results previously considered of these effects, we expect that an investigation of the effects of moisture content and temperature on creep and stress relaxation of wood would be of interest. Of course, it is necessary first to establish the fundamental creep or relaxation behavior of wood under given conditions, and so we have investigated the static viscoelasticity of wood within low stress range in bending of Buna wood (Fagus crenata) beam. The results are as follows:Within the range of strain observed in this experiment, the stress-strain relation is linear and creep compliance, recovery compliance and relaxation modulus are independent of magnitude of loads. This facts suggests that wood behaves as a linear viscoelastic material.The scale factor of wet wood parallel to grain amounts to as much as four times of air dry wood. Such an influence of water sorption on creep behavior is discussed in connection with the variation in moisture effects on dynamic behavior of Buna wood and on stress relaxation of Hinoki wood treated by formaldehyde.The curves of D(t) or E(t) vs. logt of wood that are determind at different temperatures have been tried to be superposed by means of a horizontal translation along the logarithmic time axis and the result was found uncomplete. But when these curves are smoothed out and differentiated by logt, the shape of the curves obtained are analogous to the relaxation time spectra measured for long time scale. The temperature dependency of the shift factor is hereby discussed.