Extrusion Rheology Research Articles

Changes in gelation, aggregation and intermolecular forces in frozen-thawed egg yolks during freezing

The changes in gelation, aggregation and intermolecular forces in frozen-thawed egg yolks during freezing were determined to clarify the mechanism of frozen-induced egg yolk gel formation. The results indicated that the frozen-thawed egg yolks lost their fluidity after 6 h of freezing, as shown in the graph. Back extrusion rheology showed that the yolk viscosity and consistency increased significantly when the egg yolk was frozen for the designated amount of time (1, 2, 3, 4, 5, and 6 h). The gel strength, hardness and adhesiveness of egg yolks frozen for 7–12 h tended to increase. Turbidity analysis results indicated that the turbidity of frozen-thawed egg yolks significantly increased, but SDS-PAGE results showed that the protein patterns of the frozen-thawed egg yolks did not change during freezing. Upon gelation of the frozen-thawed yolks, the free sulfhydryl content in the frozen-thawed egg yolks decreased significantly, and the content of disulfide bonds initially increased and then slightly decreased. There was no significant difference between the surface sulfhydryl content and the surface hydrophobicity of the frozen-thawed egg yolks, but both were higher than those of fresh egg yolks. The results of the analysis of intermolecular forces demonstrated that hydrophobic interactions, hydrogen bonding, and interactions between hydrophobic groups and disulfide bonds could stabilize the protein gel network. Raman spectroscopy further revealed that the secondary structures of egg yolk proteins changed. These results suggested that the characteristic gel of frozen-thawed egg yolks was formed as a result of multiple interactions among protein molecules.

Insights into material design, extrusion rheology, and properties of 3D-printable alkali-activated fly ash-based binders

Material design of alkali activated fly ash-based binders for extrusion-based 3D printing, the rheological responses that are influential in ensuring printability, and the properties of such binders are discussed in this paper. Fly ash is supplemented with fine limestone, slag, or portland cement to provide adequate microstructural packing required for printability. The alkaline activators help reduce the yield stress and enhance the cohesiveness of the mixtures. Based on the measured shear yield stress at different times and concurrent printing of a filament, the printability window and yield stress bounds for printability, applicable for the chosen printing parameters, are established. This approach could be used for mixture qualification for extrusion-based printing. The Benbow-Bridgwater model is implemented on extrusion rheology results of pastes to determine the extrusion yield stress and wall slip shear stress, which are useful process-related parameters. It is shown that these parameters can also be related to shear and extensional rheological properties of alkali-activated pastes, thus ensuring a much-needed link between parameters related to material design and the process of extrusion. Mechanical properties and pore structure similar to those of conventionally cast mixtures are achieved.

Linking fresh paste microstructure, rheology and extrusion characteristics of cementitious binders for 3D printing

AbstractCementitious binders amenable to extrusion‐based 3D printing are formulated by tailoring the fresh microstructure through the use of fine limestone powder or a combination of limestone powder and microsilica or metakaolin. Mixtures are proportioned with and without a superplasticizer to enable different particle packings at similar printability levels. A simple microstructural parameter, which implicitly accounts for the solid volume and inverse square dependence of particle size on yield stress can be used to select preliminary material combinations for printable binders. The influence of composition/microstructure on the response of pastes to extension or squeezing are also brought out. Extrusion rheology is used in conjunction with a phenomenological model to better understand the properties of significance in extrusion‐based printing of cementitious materials. The extrusion yield stress and die wall slip shear stress extracted from the model enables an understanding of their relationships with the fresh paste microstructure, which are crucial in selecting binders, extrusion geometry, and processing parameters for 3D printing.

Back Extrusion Rheology for Evaluating the Transitional Effects of High Pressure Processing of Egg Components

AbstractIn this study, a back extrusion concept was used to evaluate the rheological properties of egg components treated by high pressure processing. Rheological properties, such as viscosity index (ɳ) and apparent elasticity (Ea) of egg components, were evaluated using a central composite design with three independent variables included at five levels. The variables used were high pressure (350−550 MPa), treatment time (10–20 min) and temperature (15−35C). Apparent viscosity was also evaluated using a conventional rheology, using a parallel plate rotational viscometer. Viscosity index and apparent elasticity of various egg components were found to increase significantly (P < 0.05) with an increase in treatment intensity. A relationship between apparent viscosity (rheological) and viscosity index (textural properties) was established. It revealed positive correlations for all egg components (egg white, egg yolk and whole liquid egg) with R2 values higher than 0.95.Practical ApplicationsTextural/rheological characteristics play a significant role in determining the functional properties of whole liquid egg, egg white or egg yolk. Liquid foods are usually characterized by conventional viscometry and solid foods by their texture. The transition between liquid and solid covering the semi‐solid consistency poses measurement problems for both techniques. Back extrusion rheology can be used to bridge the gap between the two. High pressure processing allows the liquid egg components to be transformed from liquid to a gel‐like to a solid consistency, depending on the applied pressure level, temperature and time. Hence, back extrusion rheology is ideally suitable for studying texture formation in egg products during high pressure processing.

The viscosity of diesel oil and mixtures with straight vegetable oils: Palm, cabbage palm, cotton, groundnut, copra and sunflower

The feed back experience of using straight vegetable oil (SVO) as a fuel in the existing diesel engines evidences the need for fitting several physical properties, among them the fuel viscosity. An empirical modelling is proposed in order to interpolate viscosity to any kind of diesel oil/SVO blend. This model is fitted on an experimental viscosity database on blends, varying the SVO mass proportion in the blend, the blend temperature between cloud point and 353 K, and including six vegetable oils varying the fatty acids composition. Extrusion rheology was also checked by varying the pressure drop. Measurements show that blends behave Newtonian.

The influence of powder packing on the rheology of fibre-loaded pastes

The effects of fibre addition on the extrusion rheology of ceramic particulate pastes has been investigated using model pastes containing chopped glass fibre and alumina powders. In these pastes where the fibre diameter was much larger than the alumina particle diameter, there was a decrease in the pressure required to extrude the paste as the powder component was replaced by fibre, up to a ratio of 0.4 powder to 0.6 fibre by volume. When the pastes were characterized using physically based models this behaviour was reflected in lower values of the derived rheological parameters. It is shown that this behaviour can largely be attributed to the packing behaviour of the fibre and powder-phase components. The results also suggest that the presence of fibres increases the die entry pressure drop relative to the die land pressure drop. It is shown that while the models proposed by Milewski in combination with the rheological models can be used to illustrate the expected behaviour of composite pastes, the observed behaviour was better predicted by using modified models proposed by Karlsson and Spring. At high fibre loadings (>60 vol%), extrudable materials could not be formed; this was attributed to packing and mixing problems leading to increased fibre-fibre interaction preventing flow. This is highlighted by materials in which the ratio of powder to fibre was 1 to 4 by volume, where the paste-like body was compressible and exhibited some elastic springback. For pastes where the solid phase contains <50 vol% fibre the rheological behaviour is predictable if the packing behaviour of the fibre and the rheological behaviour of the pastes containing only the powder are known. This can be used as a tool to aid the design of composite pastes and for the development of suitable process equipment.

The extrusion rheology of dehydrated potato

The rheologies of different dehydrated potato granules are often compared using the Brabender viscoamylograph. The resulting pasting characteristics are not readily applicable to low moisture extrusion-cooking, particularly in combination with starch-based additives. This paper describes the rheological behaviour of different potato granule types singly and when mixed with additives at low moisture contents using capillary rheometry and compaction techniques. The pilot-scale, single-screw extrusion of these materials shows the marked effect of the additives on the operating conditions. The relationship between the frictional properties of the feed material and the pressure generation in the extruder is emphasized.

LITERATURE ABSTRACTS

GENERAL PRINCIPLES: Observations on the Action of the F.M.C. Pea Tenderometer Relating to Standardization of the Instrument. P. W. Voisey and M. Kloek.GENERAL PRINCIPLES: Engineering Analysis of Soy Dough Rheology in Extrusion. Y. C. Jao, A. H. Chen, D. Lewandowski and W. E. IrwinGENERAL PRINCIPLES: Design and Modeling of a Capillary Food Extruder. R. G. Morgan, D. A. Suter and V. E. Sweat.INSTRUMENTATION AND METHODOLOGY: Examination of Operational Aspects of Fruit Pressure Tests. P. W. VoiseyINSTRUMENTATION AND METHODOLOGY: Interaction of Indices Characterizing the Physico‐Mechanical Properties of Bread Crumb. L. Ya. Auerman and M. G. VasilevINSTRUMENTATION AND METHODOLOGY: Analysis of the Plastometer and Correlation of Bostwick Consistometer Data. M. A. Rao and M. C. Bourne.OBJECTIVE MEASUREMENTS: Quelques Donnees Sur La Texture De L'Emmenthal En Provenance De Fruitieres Diverses. F. Sauvageot, R. Mathis, G. Fagnoni, M. Marien and P. M. Lamelliere.OBJECTIVE MEASUREMENTS: Spreadability and Rheological Characteristics of Some Fondu Cheeses. F. Sauvageot and A. M. Piolet.OBJECTIVE MEASUREMENTS: Bulk Compression Testing of Peaches to Assess Texture. R. C. Clark and V. N. M. Rao.FACTORS AFFECTING TEXTURE: Distribution of Molecular Species of Collagen in Muscle and the Relationship to Meat Texture. (Lecture); A. G. Bailey.FACTORS AFFECTING TEXTURE: The Structure of Peaches and Pavias After Various Freezing and Thawing Treatments. Relation with quality (Lecture). P. A. Phan and V.‐X. Nguyen.FACTORS AFFECTING TEXTURE: Some Rheological Properties of a Cheese‐like Product Prepared by Direct Acidification. J. R. Rosenau, J. F. Calzada and M. Peleg.RELATIONSHIP TO STRUCTURE: Scanning Electron Microscopy of Cooked Spaghetti. J. E. Dexter, B. L. Dronzek and R. R. Matsuo.

Extrusion rheology of rigid PVC

Two compounds or rigid PVC, one of the emulsion type, the other of the suspension type, were processed at different temperatures by means of a highly instrumented 30-mm research extruder. During processing, measurements were made of the axial distribution of pressures and temperatures at the inner wall of the barrel, of the axial temperature distribution in the hollow screw and of the radial temperature distribution of the melt close to the screw tip.

Extrusion Rheology of Lubricated Polytetrafluoroethylene

Polytetrafluoroethylene is probably the only polymer which is commercially extruded in solid state. The polymer is provided in powder form which is lubricated by an oil. The samples of this study were powder of about 500 μ size, coagulated from latex particles of average .2–.4 μ. Naphtha was used as the lubricant at 16.5 weight percent of the composition. The pressure-output rate relation was examined with two types of capillary rheometers. A constant pressure rheometer was used to characterize the pressure range of 1000 3000 psi. The output rate at a given pressure decreased with time. A constant drive speed rheometer was used in the pressure range of 4000–14,000 psi. The recording of the force was very irregular but had an oscillating pattern. With both rheometers the extrudate diameters were equal or smaller than the die diameter. The compression experiment showed that the material behavior was dependent on not only the available free volume but the nature of powder itself. The compressive stress relaxation, however, depended on the free volume only. Recovery from compression was almost perfect.