The Experts below are selected from a list of 10668 Experts worldwide ranked by ideXlab platform
Stefan Markus Schmalholz - One of the best experts on this subject based on the ideXlab platform.
-
Thermal Softening induced subduction initiation at a passive margin
Geophysical Journal International, 2020Co-Authors: Daniel Kiss, Lorenzo Candioti, Thibault Duretz, Stefan Markus SchmalholzAbstract:We present 2-D numerical simulations of convergence at a hyperextended passive margin with exhumed subcontinental mantle. We consider viscoelasto-plastic deformation, heat transfer and thermomechanical coupling by shear heating and associated Thermal Softening due to temperature dependent viscosity. The simulations show subduction initiation for convergence velocities of 2 cm yr−1, initial Moho temperatures of 525 °C and maximal deviatoric stresses of ca. 800 MPa, around the Moho, prior to localization. Subduction initiates in the region with thinned continental crust and is controlled by a Thermally activated ductile shear zone in the mantle lithosphere. The shear zone temperature can be predicted with a recently published analytical expression. The criterion for subduction initiation is a temperature difference of at least 225 °C between predicted temperature and initial Moho temperature. The modelled forced subduction broadly agrees with geological data and reconstructions of subduction during closure of the Piemont-Liguria basin, caused by convergence of the European and Adriatic plates during the Alpine orogeny.
-
Spontaneous generation of ductile shear zones by Thermal Softening: Localization criterion, 1D to 3D modelling and application to the lithosphere
Earth and Planetary Science Letters, 2019Co-Authors: Daniel Kiss, Thibault Duretz, Yuri Podladchikov, Stefan Markus SchmalholzAbstract:The generation of ductile shear zones is essential for the formation of tectonic plate boundaries, such as subduction or strike-slip zones. However, the primary mechanism of ductile strain localization is still contentious. We study here the spontaneous generation of ductile shear zones by Thermal Softening using thermo-mechanical numerical simulations for linear and power-law viscous flow in one-dimension (1D), 2D and 3D. All models are velocity-driven. The 1D model exhibits bulk simple shear whereas the 2D and 3D models exhibit bulk pure shear. The initial conditions include a small temperature perturbation in otherwise homogeneous material. We use a series of 1D simulations to determine a new analytical formula which predicts the temperature evolution inside the shear zone. This temperature prediction requires knowledge of only the boundary velocity, flow law and Thermal parameters, but no a priori information about the shear zone itself, such as thickness, stress and strain rate. The prediction is valid for 1D, 2D and 3D shear zones in bulk pure and simple shear. The results show that shear heating dominates over conductive cooling if the relative temperature increase is >50 °C. The temperature variation induced by the shear zone is nearly one order of magnitude wider than the corresponding finite strain variation so that no significant temperature variation occurs between shear zone and wall rock. Applying typical flow laws for lithospheric rocks shows that shear zone generation by Thermal Softening occurs for typical plate tectonic velocities of few cm.yr−1 or strain rates between and s−1. Shear stresses larger than 200 MPa can already cause strain localization. The results indicate that Thermal Softening is a feasible mechanism for spontaneous ductile shear zone generation in the lithosphere and may be one of the primary mechanisms of lithospheric strain localization.
-
Thermal Softening Induced Strain Localization, a Possible Mechanism of Lithospheric Scale Shear Zone Formation and Subduction Initiation
2018Co-Authors: Daniel Kiss, Lorenzo Candioti, Thibault Duretz, Yuri Podlachikov, Stefan Markus SchmalholzAbstract:Active plate tectonics, characterized by excessive areas of no or little deformation divided by localized areas of intense deformation, is a distinctive feature of our planet. Despite its importance, the physics of lithospheric scale shear zone formation and subduction initiation is still incompletely understood. We focus on two major challenges, that are: (1) To find a mechanism of spontaneous shear localization without prescribing the shear zone. (2) Based on experimentally derived flow-laws of olivine, the upper and hence colder part of the mantle must be very strong. In fact, the stresses required to deform a yet intact and cold mantle are difficult to reach and maintain without a Softening mechanism. In this study we discuss the possible role of Thermal Softening in subduction initiation. Thermal Softening is a result of the conversion of mechanical work into heat (i.e. shear heating) and of the temperature dependence of rock viscosities. Previous studies have shown that Thermal Softening can cause strain localization and the formation of large-offset shear zones in ductile materials whose deformation behavior is described with creep flow laws (e.g. dislocation creep). Also, it has been shown that Thermal Softening induced shear localization can result in significant stress drops of a few hundred MPa. We present a one-dimensional (1D), simple shear model that helps both qualitative and quantitative understanding of the first order characteristics of shear zone evolution. We show the general applicability of the 1D simple-shear model by comparing it’s results with 2D and 3D of shear zone development under far-field pure shear. Finally, we compare the results of the simple shear zone models with results of high resolution numerical simulations of Alpine lithospheric deformation. In these simulations, first we model the formation of hyper-extended passive margins and mantle exhumation by extending a continental lithosphere. After a period of Thermal relaxation, we start to compress the resulted configuration which leads to subduction initiation. From the onset of the subduction until the continent-continent collision a strong positive Thermal anomaly, associated with Thermal Softening, is located at the subduction interface.
-
Spontaneous ductile crustal shear zone formation by Thermal Softening and related stress, temperature and strain rate evolution
Tectonophysics, 2018Co-Authors: Yoann Jaquet, Stefan Markus SchmalholzAbstract:Abstract Ductile crustal shear zones play an important role during the formation of orogenic wedges but the Softening mechanism controlling their formation and evolution are still debated. We perform two-dimensional thermo-mechanical numerical simulations of lithospheric shortening, including an underlying asthenosphere, to investigate the mechanism for ductile shear localization and to quantify the evolution of differential stress, temperature and strain rate inside shear zones that form in the ductile part of the upper crust. The simulations show the development of an intra-continental subduction zone whereby the lower crust and mantle lithosphere subduct beneath the adjacent mantle lithosphere. The upper crust forms a doubly-vergent wedge in which shear zones form subsequently. Shear zone formation is exclusively caused by Thermal Softening due to shear heating and temperature dependent viscosity, and is initiated by locally elevated shear stresses. The shear zone thickness is physics-controlled, hence mesh-insensitive and numerically resolved in the simulations. Temperature increase inside crustal shear zones is ca. 100 °C. The tectonic overpressure inside upper crustal shear zones is up to 250 MPa and can be twice the value of the corresponding deviatoric stress. Stresses inside the shear zone decrease during its formation and are hence smaller inside the shear zone than outside. Surface processes influence the location and orientation of shear zones, but not their formation and propagation by Thermal Softening. The numerically calculated differential stress (30–260 MPa), temperature (280–380 °C) and strain rate (∼ 10 −13 s −1 ) inside ductile crustal shear zones agree with corresponding estimates for natural shear zones. This agreement between modelled differential stress, temperature and strain rate with corresponding natural estimates supports previous results which indicate that Thermal Softening is a controlling Softening mechanism for natural shear zone formation.
-
Formation of orogenic wedges and crustal shear zones by Thermal Softening, associated topographic evolution and application to natural orogens
Tectonophysics, 2018Co-Authors: Yoann Jaquet, Thibault Duretz, Djordje Grujic, Henri Masson, Stefan Markus SchmalholzAbstract:Abstract The model of an orogenic wedge has been applied to explain the tectonic evolution of many orogens worldwide. Orogenic wedges are characterized by (1) a first-order shear zone which underthrusts the mantle lithosphere and lower crust beneath the adjacent mantle lithosphere and (2) a sequence of second-order upper crustal shear zones which form tectonic nappes. Shear zone formation in the lithosphere is, however, incompletely understood. We perform two dimensional thermo-mechanical numerical simulations of lithospheric shortening to study shear zone formation, propagation and associated wedge formation. The only perturbation in the model lithosphere is a different temperature at the left (1300 ° C) and right (1400 ° C) half of the model bottom. Despite this smooth and weak perturbation, simulations show self-consistent and spontaneous formation of first- and second-order shear zones generating an orogenic wedge. The shear zones are caused by Thermal Softening and temperature-dependent rock viscosity. Lateral spacing of upper crustal shear zones spans between 30 and 50 km and is controlled by the depth of the boundary between upper and lower crust which acts as mechanical detachment level. Modelled upper crustal shear zones are active for ∼1 to ∼4 My. Surface processes such as sedimentation and erosion influence shear zone orientation, spacing and duration but do not impact fundamental processes of shear zone formation and propagation. Simulations produce both singly-vergent and doubly-vergent wedges. Topographic uplift rates are controlled by the applied bulk shortening rate. The modelled surface uplift and subsidence associated with crustal shear zones could explain major consecutive thrusting events and related sedimentation within flexural basins during the formation of the Helvetic nappe system in Western Switzerland. Furthermore, results for shear zone propagation along a mid-crustal detachment and associated uplift of crustal basement could potentially explain foreland basement-cored uplifts in natural orogens such as the Laramide orogen, Taiwan or the Shillong Plateau.
Shajahan Shanavas - One of the best experts on this subject based on the ideXlab platform.
-
Kinetics of Thermal Softening of cassava tubers and rheological modeling of the starch
Journal of Food Science and Technology, 2010Co-Authors: Moothandassery Sankarakutty Sajeev, Manju Unnikrishnan, Sujatha Narayana Moorthy, Jeyan Sreekumar, Shajahan ShanavasAbstract:Cassava or tapioca ( Manihot esculenta Crantz) tubers having high amount of carbohydrate are utilized after boiling or processing into starch and flour. Textural properties of raw and cooked tubers depend on variety, maturity, growing environment, physico-chemical and starch properties. Starch is used in food preparations as gelling and thickening agent, stabilizer and texture modifier. This study aims at analyzing and modeling the textural, dynamic rheological and gelatinization properties of selected cassava varieties. The Thermal Softening behavior was analyzed by linear regression and fractional conversion techniques, rheological properties of the gelated starch by Maxwell and power law models. The varieties were classified based on their physico-chemical, texture profile, rheological and gelatinization properties by multivariate analysis. The textural, rheological and gelatinization properties were significantly affected by the varieties ( p
-
Kinetics of Thermal Softening of cassava tubers and rheological modeling of the starch
Journal of Food Science and Technology, 2010Co-Authors: Moothandassery Sankarakutty Sajeev, Manju Unnikrishnan, Sujatha Narayana Moorthy, Jeyan Sreekumar, Shajahan ShanavasAbstract:Cassava or tapioca (Manihot esculenta Crantz) tubers having high amount of carbohydrate are utilized after boiling or processing into starch and flour. Textural properties of raw and cooked tubers depend on variety, maturity, growing environment, physico-chemical and starch properties. Starch is used in food preparations as gelling and thickening agent, stabilizer and texture modifier. This study aims at analyzing and modeling the textural, dynamic rheological and gelatinization properties of selected cassava varieties. The Thermal Softening behavior was analyzed by linear regression and fractional conversion techniques, rheological properties of the gelated starch by Maxwell and power law models. The varieties were classified based on their physico-chemical, texture profile, rheological and gelatinization properties by multivariate analysis. The textural, rheological and gelatinization properties were significantly affected by the varieties (p < 0.05). Thermal Softening of tubers was modeled by dual mechanism first order kinetic model with rate constant values ranging from 0.081 to 0.105 min(-1). Linear regression models with extremely good fit were obtained to explain the relationship between the degree of cooking and relative firmness. The dynamic spectra of the gelated starch showed the characteristics of concentrated biopolymer dispersion and described using Maxwell and power law model. The results showed that textural, rheological and gelatinization properties varied considerably among the varieties and besides the physico-chemical properties, interaction between them and structural make up of the tuber parenchyma had a great influence on cooking quality and rheological properties.
Daniel Kiss - One of the best experts on this subject based on the ideXlab platform.
-
Thermal Softening induced subduction initiation at a passive margin
Geophysical Journal International, 2020Co-Authors: Daniel Kiss, Lorenzo Candioti, Thibault Duretz, Stefan Markus SchmalholzAbstract:We present 2-D numerical simulations of convergence at a hyperextended passive margin with exhumed subcontinental mantle. We consider viscoelasto-plastic deformation, heat transfer and thermomechanical coupling by shear heating and associated Thermal Softening due to temperature dependent viscosity. The simulations show subduction initiation for convergence velocities of 2 cm yr−1, initial Moho temperatures of 525 °C and maximal deviatoric stresses of ca. 800 MPa, around the Moho, prior to localization. Subduction initiates in the region with thinned continental crust and is controlled by a Thermally activated ductile shear zone in the mantle lithosphere. The shear zone temperature can be predicted with a recently published analytical expression. The criterion for subduction initiation is a temperature difference of at least 225 °C between predicted temperature and initial Moho temperature. The modelled forced subduction broadly agrees with geological data and reconstructions of subduction during closure of the Piemont-Liguria basin, caused by convergence of the European and Adriatic plates during the Alpine orogeny.
-
Spontaneous generation of ductile shear zones by Thermal Softening: Localization criterion, 1D to 3D modelling and application to the lithosphere
Earth and Planetary Science Letters, 2019Co-Authors: Daniel Kiss, Thibault Duretz, Yuri Podladchikov, Stefan Markus SchmalholzAbstract:The generation of ductile shear zones is essential for the formation of tectonic plate boundaries, such as subduction or strike-slip zones. However, the primary mechanism of ductile strain localization is still contentious. We study here the spontaneous generation of ductile shear zones by Thermal Softening using thermo-mechanical numerical simulations for linear and power-law viscous flow in one-dimension (1D), 2D and 3D. All models are velocity-driven. The 1D model exhibits bulk simple shear whereas the 2D and 3D models exhibit bulk pure shear. The initial conditions include a small temperature perturbation in otherwise homogeneous material. We use a series of 1D simulations to determine a new analytical formula which predicts the temperature evolution inside the shear zone. This temperature prediction requires knowledge of only the boundary velocity, flow law and Thermal parameters, but no a priori information about the shear zone itself, such as thickness, stress and strain rate. The prediction is valid for 1D, 2D and 3D shear zones in bulk pure and simple shear. The results show that shear heating dominates over conductive cooling if the relative temperature increase is >50 °C. The temperature variation induced by the shear zone is nearly one order of magnitude wider than the corresponding finite strain variation so that no significant temperature variation occurs between shear zone and wall rock. Applying typical flow laws for lithospheric rocks shows that shear zone generation by Thermal Softening occurs for typical plate tectonic velocities of few cm.yr−1 or strain rates between and s−1. Shear stresses larger than 200 MPa can already cause strain localization. The results indicate that Thermal Softening is a feasible mechanism for spontaneous ductile shear zone generation in the lithosphere and may be one of the primary mechanisms of lithospheric strain localization.
-
Thermal Softening Induced Strain Localization, a Possible Mechanism of Lithospheric Scale Shear Zone Formation and Subduction Initiation
2018Co-Authors: Daniel Kiss, Lorenzo Candioti, Thibault Duretz, Yuri Podlachikov, Stefan Markus SchmalholzAbstract:Active plate tectonics, characterized by excessive areas of no or little deformation divided by localized areas of intense deformation, is a distinctive feature of our planet. Despite its importance, the physics of lithospheric scale shear zone formation and subduction initiation is still incompletely understood. We focus on two major challenges, that are: (1) To find a mechanism of spontaneous shear localization without prescribing the shear zone. (2) Based on experimentally derived flow-laws of olivine, the upper and hence colder part of the mantle must be very strong. In fact, the stresses required to deform a yet intact and cold mantle are difficult to reach and maintain without a Softening mechanism. In this study we discuss the possible role of Thermal Softening in subduction initiation. Thermal Softening is a result of the conversion of mechanical work into heat (i.e. shear heating) and of the temperature dependence of rock viscosities. Previous studies have shown that Thermal Softening can cause strain localization and the formation of large-offset shear zones in ductile materials whose deformation behavior is described with creep flow laws (e.g. dislocation creep). Also, it has been shown that Thermal Softening induced shear localization can result in significant stress drops of a few hundred MPa. We present a one-dimensional (1D), simple shear model that helps both qualitative and quantitative understanding of the first order characteristics of shear zone evolution. We show the general applicability of the 1D simple-shear model by comparing it’s results with 2D and 3D of shear zone development under far-field pure shear. Finally, we compare the results of the simple shear zone models with results of high resolution numerical simulations of Alpine lithospheric deformation. In these simulations, first we model the formation of hyper-extended passive margins and mantle exhumation by extending a continental lithosphere. After a period of Thermal relaxation, we start to compress the resulted configuration which leads to subduction initiation. From the onset of the subduction until the continent-continent collision a strong positive Thermal anomaly, associated with Thermal Softening, is located at the subduction interface.
Thibault Duretz - One of the best experts on this subject based on the ideXlab platform.
-
Thermal Softening induced subduction initiation at a passive margin
Geophysical Journal International, 2020Co-Authors: Daniel Kiss, Lorenzo Candioti, Thibault Duretz, Stefan Markus SchmalholzAbstract:We present 2-D numerical simulations of convergence at a hyperextended passive margin with exhumed subcontinental mantle. We consider viscoelasto-plastic deformation, heat transfer and thermomechanical coupling by shear heating and associated Thermal Softening due to temperature dependent viscosity. The simulations show subduction initiation for convergence velocities of 2 cm yr−1, initial Moho temperatures of 525 °C and maximal deviatoric stresses of ca. 800 MPa, around the Moho, prior to localization. Subduction initiates in the region with thinned continental crust and is controlled by a Thermally activated ductile shear zone in the mantle lithosphere. The shear zone temperature can be predicted with a recently published analytical expression. The criterion for subduction initiation is a temperature difference of at least 225 °C between predicted temperature and initial Moho temperature. The modelled forced subduction broadly agrees with geological data and reconstructions of subduction during closure of the Piemont-Liguria basin, caused by convergence of the European and Adriatic plates during the Alpine orogeny.
-
Spontaneous generation of ductile shear zones by Thermal Softening: Localization criterion, 1D to 3D modelling and application to the lithosphere
Earth and Planetary Science Letters, 2019Co-Authors: Daniel Kiss, Thibault Duretz, Yuri Podladchikov, Stefan Markus SchmalholzAbstract:The generation of ductile shear zones is essential for the formation of tectonic plate boundaries, such as subduction or strike-slip zones. However, the primary mechanism of ductile strain localization is still contentious. We study here the spontaneous generation of ductile shear zones by Thermal Softening using thermo-mechanical numerical simulations for linear and power-law viscous flow in one-dimension (1D), 2D and 3D. All models are velocity-driven. The 1D model exhibits bulk simple shear whereas the 2D and 3D models exhibit bulk pure shear. The initial conditions include a small temperature perturbation in otherwise homogeneous material. We use a series of 1D simulations to determine a new analytical formula which predicts the temperature evolution inside the shear zone. This temperature prediction requires knowledge of only the boundary velocity, flow law and Thermal parameters, but no a priori information about the shear zone itself, such as thickness, stress and strain rate. The prediction is valid for 1D, 2D and 3D shear zones in bulk pure and simple shear. The results show that shear heating dominates over conductive cooling if the relative temperature increase is >50 °C. The temperature variation induced by the shear zone is nearly one order of magnitude wider than the corresponding finite strain variation so that no significant temperature variation occurs between shear zone and wall rock. Applying typical flow laws for lithospheric rocks shows that shear zone generation by Thermal Softening occurs for typical plate tectonic velocities of few cm.yr−1 or strain rates between and s−1. Shear stresses larger than 200 MPa can already cause strain localization. The results indicate that Thermal Softening is a feasible mechanism for spontaneous ductile shear zone generation in the lithosphere and may be one of the primary mechanisms of lithospheric strain localization.
-
Thermal Softening Induced Strain Localization, a Possible Mechanism of Lithospheric Scale Shear Zone Formation and Subduction Initiation
2018Co-Authors: Daniel Kiss, Lorenzo Candioti, Thibault Duretz, Yuri Podlachikov, Stefan Markus SchmalholzAbstract:Active plate tectonics, characterized by excessive areas of no or little deformation divided by localized areas of intense deformation, is a distinctive feature of our planet. Despite its importance, the physics of lithospheric scale shear zone formation and subduction initiation is still incompletely understood. We focus on two major challenges, that are: (1) To find a mechanism of spontaneous shear localization without prescribing the shear zone. (2) Based on experimentally derived flow-laws of olivine, the upper and hence colder part of the mantle must be very strong. In fact, the stresses required to deform a yet intact and cold mantle are difficult to reach and maintain without a Softening mechanism. In this study we discuss the possible role of Thermal Softening in subduction initiation. Thermal Softening is a result of the conversion of mechanical work into heat (i.e. shear heating) and of the temperature dependence of rock viscosities. Previous studies have shown that Thermal Softening can cause strain localization and the formation of large-offset shear zones in ductile materials whose deformation behavior is described with creep flow laws (e.g. dislocation creep). Also, it has been shown that Thermal Softening induced shear localization can result in significant stress drops of a few hundred MPa. We present a one-dimensional (1D), simple shear model that helps both qualitative and quantitative understanding of the first order characteristics of shear zone evolution. We show the general applicability of the 1D simple-shear model by comparing it’s results with 2D and 3D of shear zone development under far-field pure shear. Finally, we compare the results of the simple shear zone models with results of high resolution numerical simulations of Alpine lithospheric deformation. In these simulations, first we model the formation of hyper-extended passive margins and mantle exhumation by extending a continental lithosphere. After a period of Thermal relaxation, we start to compress the resulted configuration which leads to subduction initiation. From the onset of the subduction until the continent-continent collision a strong positive Thermal anomaly, associated with Thermal Softening, is located at the subduction interface.
-
Formation of orogenic wedges and crustal shear zones by Thermal Softening, associated topographic evolution and application to natural orogens
Tectonophysics, 2018Co-Authors: Yoann Jaquet, Thibault Duretz, Djordje Grujic, Henri Masson, Stefan Markus SchmalholzAbstract:Abstract The model of an orogenic wedge has been applied to explain the tectonic evolution of many orogens worldwide. Orogenic wedges are characterized by (1) a first-order shear zone which underthrusts the mantle lithosphere and lower crust beneath the adjacent mantle lithosphere and (2) a sequence of second-order upper crustal shear zones which form tectonic nappes. Shear zone formation in the lithosphere is, however, incompletely understood. We perform two dimensional thermo-mechanical numerical simulations of lithospheric shortening to study shear zone formation, propagation and associated wedge formation. The only perturbation in the model lithosphere is a different temperature at the left (1300 ° C) and right (1400 ° C) half of the model bottom. Despite this smooth and weak perturbation, simulations show self-consistent and spontaneous formation of first- and second-order shear zones generating an orogenic wedge. The shear zones are caused by Thermal Softening and temperature-dependent rock viscosity. Lateral spacing of upper crustal shear zones spans between 30 and 50 km and is controlled by the depth of the boundary between upper and lower crust which acts as mechanical detachment level. Modelled upper crustal shear zones are active for ∼1 to ∼4 My. Surface processes such as sedimentation and erosion influence shear zone orientation, spacing and duration but do not impact fundamental processes of shear zone formation and propagation. Simulations produce both singly-vergent and doubly-vergent wedges. Topographic uplift rates are controlled by the applied bulk shortening rate. The modelled surface uplift and subsidence associated with crustal shear zones could explain major consecutive thrusting events and related sedimentation within flexural basins during the formation of the Helvetic nappe system in Western Switzerland. Furthermore, results for shear zone propagation along a mid-crustal detachment and associated uplift of crustal basement could potentially explain foreland basement-cored uplifts in natural orogens such as the Laramide orogen, Taiwan or the Shillong Plateau.
-
Dramatic effect of elasticity on Thermal Softening and strain localization during lithospheric shortening
Geophysical Journal International, 2015Co-Authors: Yoann Jaquet, Thibault Duretz, Stefan Markus SchmalholzAbstract:We present two-dimensional numerical simulations for shortening a viscoelastoplastic lithosphere to quantify the impact of elasticity on strain localization due to Thermal Softening. The model conserves energy and mechanical work is converted into heat or stored as elastic strain energy. For a shear modulus G = 10^10 Pa, a prominent lithospheric shear zone forms and elastic energy release increases the localization intensity (strain rate amplification). For G = 5 × 10^10 Pa shear zones still form but deformation is less localized. For G = 10^12 Pa, the lithosphere behaves effectively viscoplastic and no shear zones form during homogeneous thickening. Maximal shearing-related increase of surface heat flux is 15-25 mW.m^−2 and of temperature at lower crustal depth is ∼150 °C, whereby these peak values are transient (0.1-1 My). Elasticity and related energy release can significantly contribute to strain localization and plate-like behaviour of the lithosphere required for plate tectonics.
Moothandassery Sankarakutty Sajeev - One of the best experts on this subject based on the ideXlab platform.
-
Kinetics of Thermal Softening of cassava tubers and rheological modeling of the starch
Journal of Food Science and Technology, 2010Co-Authors: Moothandassery Sankarakutty Sajeev, Manju Unnikrishnan, Sujatha Narayana Moorthy, Jeyan Sreekumar, Shajahan ShanavasAbstract:Cassava or tapioca ( Manihot esculenta Crantz) tubers having high amount of carbohydrate are utilized after boiling or processing into starch and flour. Textural properties of raw and cooked tubers depend on variety, maturity, growing environment, physico-chemical and starch properties. Starch is used in food preparations as gelling and thickening agent, stabilizer and texture modifier. This study aims at analyzing and modeling the textural, dynamic rheological and gelatinization properties of selected cassava varieties. The Thermal Softening behavior was analyzed by linear regression and fractional conversion techniques, rheological properties of the gelated starch by Maxwell and power law models. The varieties were classified based on their physico-chemical, texture profile, rheological and gelatinization properties by multivariate analysis. The textural, rheological and gelatinization properties were significantly affected by the varieties ( p
-
Kinetics of Thermal Softening of cassava tubers and rheological modeling of the starch
Journal of Food Science and Technology, 2010Co-Authors: Moothandassery Sankarakutty Sajeev, Manju Unnikrishnan, Sujatha Narayana Moorthy, Jeyan Sreekumar, Shajahan ShanavasAbstract:Cassava or tapioca (Manihot esculenta Crantz) tubers having high amount of carbohydrate are utilized after boiling or processing into starch and flour. Textural properties of raw and cooked tubers depend on variety, maturity, growing environment, physico-chemical and starch properties. Starch is used in food preparations as gelling and thickening agent, stabilizer and texture modifier. This study aims at analyzing and modeling the textural, dynamic rheological and gelatinization properties of selected cassava varieties. The Thermal Softening behavior was analyzed by linear regression and fractional conversion techniques, rheological properties of the gelated starch by Maxwell and power law models. The varieties were classified based on their physico-chemical, texture profile, rheological and gelatinization properties by multivariate analysis. The textural, rheological and gelatinization properties were significantly affected by the varieties (p < 0.05). Thermal Softening of tubers was modeled by dual mechanism first order kinetic model with rate constant values ranging from 0.081 to 0.105 min(-1). Linear regression models with extremely good fit were obtained to explain the relationship between the degree of cooking and relative firmness. The dynamic spectra of the gelated starch showed the characteristics of concentrated biopolymer dispersion and described using Maxwell and power law model. The results showed that textural, rheological and gelatinization properties varied considerably among the varieties and besides the physico-chemical properties, interaction between them and structural make up of the tuber parenchyma had a great influence on cooking quality and rheological properties.
