Casson Viscosity Research Articles

Quality attributes of dark chocolates formulated with palm sap-based sugar as nutritious and natural alternative sweetener

Consumer demand for healthier alternative sweeteners and attempts to replace the most common sweetener used in chocolate, namely sucrose, continue to increase in recent times. One sucrose alternative that has not been fully explored in chocolate is palm sap-based sugar. This work investigated the impact of sucrose replacement by coconut sugar (CCS1 and CCS2) and palm sugar (CPS1, CPS2 and CPS3) on the quality attributes of dark chocolate, more particularly colour, hardness, flow behaviour and aroma profile. The results showed that chocolates formulated with palm sap-based sugar were lighter in colour and harder than the reference chocolate made with sucrose, which could be attributed to a lower particle density and a higher moisture of palm sap-based sugar than that of sucrose. Analysis of the major volatile compounds recorded the presence of 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP) and high concentration of pyrazine-based compounds in the palm sap-based sugar-sweetened chocolates. The former compound (DDMP) was, however, absent in the sucrose-sweetened dark chocolate. The physicochemical properties of the sugars also had a significant effect on the rheological behaviour of the final chocolates with chocolates formulated with coconut sugar recording the highest Casson viscosity. With regard to fat melting, chocolates sweetened with palm sap-based sugar and sucrose exhibited similar melting range temperature. Palm sap-based sugar nevertheless seems to have great potential for dark chocolate applications with additional health benefits.

Viscosity prediction of cement-filler suspensions using interference model: A route for binder efficiency enhancement

Producing cementitious materials with low CO2 emissions is a key challenge for sustainability, considering the increasing demand for cement and the inefficacy of current industrial solutions. Improving the efficiency of binder use is mandatory, so that binder replacement by inert fillers with lower environmental loads is an alternative, which demands careful control of the rheological behaviour to decrease the water demand of pastes. Dispersion and packing models are well known, but other less explored parameters of raw materials (surface area, density, roughness) and paste (water content, distance between particles) determine the interaction among particles, affecting the paste's rheological behaviour.The aim of this paper is to assess the influence of inert fillers on the rheological behaviour of cementitious pastes. A range of 12 inert fillers with varied aspects was evaluated. The results indicated a good agreement between the Casson viscosity and the interference parameter calculated using the interference model.

Rheological properties, melting behaviours and physical quality characteristics of sugar-free chocolates processed using inulin/polydextrose bulking mixtures sweetened with stevia and thaumatin extracts

Demand for use of natural sweeteners and prebiotic compounds for manufacture of sugar-free chocolates has dramatically increased over the past decennium. However, their applicability in product formulation and how these will affect the flow (rheological) and physical quality characteristics still remains a big challenge. This study investigated the rheological properties, melting behaviours and other physical quality characteristics of sugar-free chocolates processed from inulin and polydextrose mixtures as bulking agents sweetened with stevia and thaumatin extracts. Standard reference chocolate was developed using sucrose and the effects of the inulin/polydextrose and stevia/thaumatin ingredients on the rheological properties, melting profiles, colour and hardness of the derived products measured using standard methods. Generally, the sugar-free chocolates showed similar flow (rheological) and melting properties as compared to the reference chocolate. Sucrose replacement with the inulin/polydextrose and stevia/thaumatin extracts resulted in significantly higher Casson viscosity. There were however no significant differences in the melting behaviour and texture of the sugar-free chocolates and the reference. Chocolates containing the sugar substitutes recorded lower onset temperatures and higher peak widths than the reference sample. Inulin and polydextrose mixtures could be used for sugar-free chocolate manufacture with satisfactory physicochemical properties when sweetened with stevia or thaumatin extracts.

Modeling of the blood rheology in steady-state shear flows

We undertake here a systematic study of the rheology of blood in steady-state shear flows. As blood is a complex fluid, the first question that we try to answer is whether, even in steady-state shear flows, we can model it as a rheologically simple fluid, i.e., we can describe its behavior through a constitutive model that involves only local kinematic quantities. Having answered that question positively, we then probe as to which non-Newtonian model best fits available shear stress vs shear-rate literature data. We show that under physiological conditions blood is typically viscoplastic, i.e., it exhibits a yield stress that acts as a minimum threshold for flow. We further show that the Casson model emerges naturally as the best approximation, at least for low and moderate shear-rates. We then develop systematically a parametric dependence of the rheological parameters entering the Casson model on key physiological quantities, such as the red blood cell volume fraction (hematocrit). For the yield stress, we base our description on its critical, percolation-originated nature. Thus, we first determine onset conditions, i.e., the critical threshold value that the hematocrit has to have in order for yield stress to appear. It is shown that this is a function of the concentration of a key red blood cell binding protein, fibrinogen. Then, we establish a parametric dependence as a function of the fibrinogen and the square of the difference of the hematocrit from its critical onset value. Similarly, we provide an expression for the Casson viscosity, in terms of the hematocrit and the temperature. A successful validation of the proposed formula is performed against additional experimental literature data. The proposed expression is anticipated to be useful not only for steady-state blood flow modeling but also as providing the starting point for transient shear, or more general flow modeling.

Assessment of rheological models for prediction of transport phenomena in stenosed artery

Hemodynamic transport in the stenosed blood vessel has been numerically investigated with five non-Newtonian rheological models. The results from Casson viscosity model, Carreau model, Cross model, power law viscosity model, and Quemada viscosity model as well as Newtonian model were compared to capture the physics at the arterial wall. At the inlet of a long artery, three different pulsating profiles are considered. Detailed flow statistics of the flow field were calculated by solving transient form of Navier-Stokes equation in an axi-symmetric domain. From the simulation data, wall shear stress and oscillatory shear index were calculated. The results show that among different rheological models, the predictions from Carreau model as well as Newtonian model differ significantly with other four models showing similar behaviour. The results demonstrate that the degree of stenoses have a significant effect on oscillatory shear index and recirculation length.

Influence of calcium fortification on physical and rheological properties of sucrose-free prebiotic milk chocolates containing inulin and maltitol.

In the present study, chocolates were investigated that had been prepared according to the composition specified as a result of this previous work (9.00% w/w inulin and 34.0% w/w maltitol) Certain physical (particle size distribution [PSD], brightness, chroma, water activity and hardness) and rheological features of the samples resulting from the addition of calcium carbonate in different quantities (300, 450, 600, 750 and 900mg calcium carbonate to 100mg milk chocolate) were studied. Both the Herschel-Bulkley and Casson models were used to investigate the rheological findings. It was determined by comparing certain rheological (rate index, Casson yield stress and Casson viscosity) and physical (chroma and hardness) parameters that samples containing 409.5mg calcium (nearly 41.0% of the RDA of calcium) per 100g chocolate did not show significant differences from samples from the control group. Furthermore, these calcium-containing samples were shown to exhibit positive differences in other physical properties (brightness and water activity) that could be noteworthy and significant with respect to visual quality and shelf life.

بررسی اثرنسبت های مختلف آرد کامل سویا به عنوان جایگزین چربی و زمان آسیاب کردن بر ویژگی های بافتی، رئولوژیکی و حسی شکلات شیری

Possibility of replacing whole soy flour for chocolate fat in chocolate production and its impact on textural, rheological and sensory properties of low fat chocolate was explored. For doing this, whole soy flour in 5 levels (0, 2,4,6,8 percent) and two refining times (105 and 135 minutes) was employed. Results indicated that longer refining time gave rise to reduction in particles size and increase in hardness of chocolate. With increasing refining time from 105 minutes to 135 minutes, hardness showed an upward trend which rose from 7100g to 8180g. Casson yield value and Casson viscosity ranged between 9.02 Pa to 35.09 Pa and 2.55 to 5.99 (Pa.s), respectively . Data revealed that whole soy flour up to 4% can be successfully substituted for chocolate fat, without causing significant difference in textural, rheological and sensory properties of chocolate samples (P<0.05). Keywords: Whole soy flour, Sensory properties, Textural properties, Rheological properties, Palm oil, Chocolate

Effect of soya milk on nutritive, antioxidative, reological and textural properties of chocolate produced in a ball mill

Chocolate is a complex rheological system in which non-fat cocoa particles and sugar particles are enveloped by crystal matrix of cocoa butter. Physical properties of chocolate depend on ingredient composition, method of production and properly performed pre-crystallization phase. In this work, chocolate was produced in an unconventional way, i.e. in a ball mill applying variable refining time (30, 60 and 90 min) and pre-crystallization temperature in chocolate masses (26, 28 and 30?C). Two types of chocolate were produced: chocolate with 20% of powdered cow?s milk (R1) and chocolate with 20% of soya milk powder (R2). The quality of chocolate was followed by comparing nutritive composition, 23 polyphenol content, hardness of chocolate, solid triglyceride content (SFC) and rheological parameters (Casson yield flow (Pa), Casson viscosity (Pas), the area of the thixotropic loop, elastic modulus and creep curves). The aim of this paper is determining changes caused by replacing cow?s milk with soya milk powder in respect of nutritive, rheological and sensory properties, as well as defining optimal parameters: precrystallization temperature and refining time of soya milk chocolate in order to obtain suitable sensory and physical properties identical to those of milk chocolate mass. The results show that replacing powdered cow?s milk with soya milk powder affects the increase in nutritive value of soya milk chocolate. R2 chocolate mass showed the increase in essential amino acids and fatty acids. This chocolate mass also showed the increase in total polyphenols by 28.1% comparing to R1 chocolate mass. By comparing viscosity, yield stress, shear stress and the area of the thixotropic loop, it can be observed that R1 chocolate mass represents a more organized and simpler system than the mass with soya milk (R2), as it shows lower values for all the above mentioned parameters, regardless of the refining time and pre-crystallization temperature. Viscoelastic behavior of R2 is also evident, as a consequence of soya protein presence. In order to maintain optimal hardness as well as melting resistance of chocolate, in case of R2 chocolate mass it is necessary to apply pre-crystallization temperature of 26?C, while for the chocolate mass R1 it is 30?C.

Rheological Properties and Phase Separation of Xanthan-Sodium Caseinate Mixtures Analyzed by a Response Surface Method

Effects of xanthan and sodium caseinate concentrations on the rheological properties of their mixture in an aqueous medium were investigated at neutral pH. It was deduced from the use of an experimental design methodology, the existence of a critical concentration of sodium caseinate, which depends on the xanthan quantity, and beyond which repulsive segregation interactions occur, generating a weakening of the elastic modulus and an embitterment of the colloidal system structure. In addition, it was observed that when the Casson viscosity value of the aqueous solution was above 0.1 Pa.s, phase separation of the system was observed. The phase diagram of the solution was established using a polynomial fit.

Effect of cocoa butter replacement with a β‐glucan‐rich hydrocolloid (C‐trim30) on the rheological and tribological properties of chocolates

AbstractBACKGROUND: The food industry has been facing the challenge of developing low‐fat and low‐calorie food products due to rising health awareness of consumers. To meet this consumer demand, an oat β‐glucan‐rich hydrocolloid (C‐trim30) was evaluated as a cocoa butter substitute in chocolates. The effects of C‐trim30 on the rheological, tribological, and textural properties of chocolates were investigated.RESULTS: The viscosity of molten chocolates increased with increasing levels of C‐trim30. Flow behaviors analyzed using the Casson model showed that the Casson viscosity and yield stress increased with increasing concentration of C‐trim30 in the chocolate. Tribological tests on a ball‐on‐flat tribometer showed a reduction in boundary coefficients of friction, with increasing C‐trim30. In addition, hardness of chocolates showed that replacement of cocoa butter with C‐trim30 produced chocolates with softer texture.CONCLUSIONS: The cocoa butter replacement with C‐trim30 up to 10% produced soft chocolates with improved boundary lubrication properties. Also, the chocolate prepared by replacing the cocoa butter with C‐trim30 resulted in a product with a lower caloric value and increased health benefits from the oat β‐glucan. Copyright © 2008 Society of Chemical Industry

GALERKIN LEAST-SQUARES APPROXIMATIONS FOR FLOWS OF CASSON FLUIDS THROUGH AN EXPANSION

Among non-Newtonian fluid models, purely viscous constitutive equations play an important role in industrial applications regardless their lack of accuracy in non-viscometric flows. In this work we are concerned with the flow of viscoplastic shear-thinning fluids in complex geometry. Viscoplastic fluids are those that behave as extremely high viscosity materials when submitted to low stresses and that flow when submitted to stresses higher than a yield stress value. Usually, they also present shearthinning behavior. Fluids such as molten chocolate, xanthan gum solutions, blood, wastewater sludges, muds, and polymer solutions present viscoplastic shear-thinning features. In order to approximate numerically viscoplastic shear-thinning flows we first describe a mechanical model based on continuum mechanics conservation laws of mass and momentum. The description of material behavior is such as to respect certain principles of objectivity and generality in continuum mechanics. The Generalized Newtonian Liquid constitutive equation with Casson viscosity function is able to predict viscoplasticity and shear-thinning. The numerical approximation of the equations is performed by a finite element method. To prevent the model from pathologies known for the classic Galerkin method, we employ a stabilized method based on a Galerkin least-squares (GLS) scheme, which is designed to circumvent Babuška-Brezzi condition and deal with the asymmetry of the advective operator. We present approximations for the flow through a planar 4:1 sudden expansion. We investigate the influence of Reynolds and Casson numbers on the flow dynamics.

Flow Behavior of Milk Chocolate Melt and the Application to Coating Flow

ABSTRACT: The rheological properties of chocolate, especially shear viscosity and yield stress, are important control parameters for enrobing processes in confectionery manufacture. The rheological parameters of molten milk chocolate were measured at 42°C during steady pipe flow using a magnetic resonance imaging (MRI) viscometric method. The experimental method combines shear rate values obtained from an MR velocity image and shear stress values obtained from an independent pressure drop measurement. The experimental factors were emulsifier type and emulsifier level. The rheogram data were fit by the Casson model to yield the Casson yield stress and plastic viscosity. The Casson yield stress ranged from 1.9 to 15.0 Pa; the Casson viscosity ranged from 6.0 to 14.6 Pa s as a function of emulsifier content. The rheological parameters were incorporated into a drainage theory model to predict coating thicknesses in the enrobing process. The model was solved numerically and yielded good approximations to the experimental values that were between 1.1 to 2.7 mm.

The Influence of Storage Time on Rheological Properties and Texture of Yoghurts with the Addition of Oat-Maltodextrin as the Fat Substitute

Yoghurts from cow's milk containing 2 kg milk fat/100 kg or 2 kg an oat-maltodextrin/100 kg (maltodextrin included 5 kg β-glucan/100 kg), were produced in a laboratory scale and stored in refrigerator conditions for 21 days. Non-fat yoghurt without addition of maltodextrin was used as a control product. The yoghurts were estimated after 1, 7, 14 and 21 day's storage. The sensory evaluation, instrumental texture profile analysis and rheological investigations were carried out, they included the determination of the flow curves and the description by Ostwald de Waele and Casson models as well as counting an apparent viscosity. Differences in the sensory quality of yoghurts containing milk fat or maltodextrin were not found, whereas these yoghurts were characterised by better sensory quality than the control product. The storage time had significant influence on the sensory evaluation and the texture parameters. During the storage time apparent viscosity of yoghurts decreased. A decrease in consistency index value, in deviation from Newtonian flow, and yield stress was noticed, whereas in Casson's viscosity of the yoghurts an increase was found.

De‐Agglomeration Kinetics of Feedstocks with Granule Tetragonal Zirconia Polycrystalline Powder

This study establishes the relationship between homogeneity of tetragonal zirconia polycrystalline (TZP) feedstocks and the kneading time in order to understand the kneading energy adsorption during the de‐agglomeration period of pre‐existing ceramic granules. Two spray‐dried Y‐TZP powders with different compress strengths were investigated using torque rheometer and transmission optical microscopy. Several properties, kneading torque (T), Casson viscosity (μ), Reynolds number (Re), and dispersive index (Ds) of the feedstocks were introduced, and monitored as a function of kneading time. Optimal processing windows were identified from the dependence of dispersive index with a power number (Np). The best shear‐kneading procedure was proposed in consideration of best feedstock homogeneity and shortest kneading time. One homogenous feedstock and two comparable cases were prepared for subsequent injection molding, debinding, sintering, and mechanical testing. The fracture strength of sintering parts by a partially homogeneous feedstock can be improved from 520 to 680 MPa by a homogeneous feedstock.

The Influence of Storage Time on Rheological Properties and Texture of Yoghurts with the Addition of Oat-Maltodextrin as the Fat Substitute

Yoghurts from cow's milk containing 2 kg milk fat/100 kg or 2 kg of an oat-maltodextrin/100 kg (maltodextrin included 5 kg b-glucan/100 kg), were weighed on a laboratory scale and stored in refrigerator conditions for 21 days. Non-fat yoghurt without the addition of maltodextrin was used as a control product. The yoghurts were analysed after 1, 7, 14, and 21 days of storage. Sensory evaluation, instrumental texture profile analysis, and rheological investigations were carried out. They included the determination of the flow curves and the description by Ostwald de Waele and Casson models as well as an account of the apparent viscosity. Differences in the sensory quality of yoghurts containing milk fat or maltodextrin were not found, whereas these yoghurts were characterized by better sensory quality than the control product. The storage time had a significant influence on the sensory evaluation and the texture parameters. During the storage time, the apparent viscosity of yoghurts decreased. A decrease in consistency index value, in deviation from Newtonian flow, and yield stress was noticed, whereas in Casson's viscosity of the yoghurts, an increase was found.

Properties of sucrose-free chocolates enriched with viable lactic acid bacteria

Chocolate formulated with isomalt and enriched with lactic acid bacteria Streptococcus thermophilus MK-10 and Lactobacillus delbrueckii subsp. bulgaricus 151, added in the form of powdered yoghurt, prepared by spray-drying is a sucrose-free, low-calorie product with functional properties. The technique of the production of chocolate sweetened with isomalt and containing live cells of the aforementioned bacterial strains has been established. Physicochemical and sensory properties of this product as well as survival of cells during 6-months storage at 4 and 18 °C have been determined. The isomalt-containing yoghurt chocolates displayed satisfactory sensory attributes. Their calorific value and consistency (hardness) were similar to those of control sucrose-free chocolates. The total acidity of yoghurt and standard milk chocolates was also similar, whereas yoghurt-containing dark chocolates displayed higher acidity. The characteristics of yoghurt-containing chocolates were a relatively low solid substance content (96.82–96.91% w/w), low Casson viscosity and yield value for milk chocolate masses, and enhanced rheological parameters for dark chocolate masses compared with control sucrose-free chocolates. Because the total number of lactic acid bacteria after 6-months storage at 4 and 18 °C was high (approximately 107 cfu/g), the sucrose-free yoghurt-containing chocolates can be regarded as functional foods.

Effect of lecithin concentration on properties of sucrose-free chocolate masses sweetened with isomalt

Rheological properties such as Casson viscosity and yield value strongly affect costs and efficiency of the chocolate making process. The addition of a proper amount of lecithin to the blend of chocolate ingredients results in a decrease of both the aforementioned parameters. However, overdosing of lecithin leads to worse sensory attributes and flow properties of the chocolate mass. Our studies on rheological properties of isomalt-containing dark chocolate masses and sucrose-containing milk chocolate masses revealed that the critical lecithin concentration was 0.9 g/100 g; and the Casson yield value of both the types of chocolate blends was enhanced above this content. The same phenomenon, i.e. chocolate thickening, was observed at lecithin concentrations of 0.4 g/100 g and 0.6 g/100 g for milk chocolate masses sweetened with isomalt, and for dark chocolate masses sweetened with sucrose, respectively.

Measurement of rheology of distiller's grain slurries using a helical impeller viscometer.

Current research is focused on developing a process to convert the cellulose and hemicellulose in distiller's grains into fermentable sugars, increasing both ethanol yield and the amount of protein in the remaining solid product. The rheologic properties of distiller's grain slurries were determined for concentrations of 21, 23, and 25%. Distiller's grain slurries are non-Newtonian, heterogeneous fluids subject to particle settling. Traditional methods of viscosity measurement, such as cone-and-plate and concentric cylinder viscometers, are not adequate for these fluids. A helical impeller viscometer was employed to measure impeller torque over a range of rotational speeds. Newtonian and non-Newtonian calibration fluids were utilized to obtain constants that relate shear stresses and shear rates to the experimental data. The Newtonian impeller constant, c, was 151; the non-Newtonian shear rate constant, k, was 10.30. Regression analysis of experimental data was utilized for comparison to power law, Herschel-Bulkley, and Casson viscosity models with regression coefficients exceeding 0.99 in all cases.

Hydrocolloids in Forming Properties of Cocoa Syrups

Agar, carrageenan, carboxymethylcellulose (CMC), and xanthan gum at diversified concentrations were used in coca syrup as stabilizer, thickener, and consistency providers. The syrups obtained in the laboratory conditions were compared to the commercial ones. Sensory evaluation of both commercial and laboratory syrups was comparable, however, the latter obtained slightly higher appraisal. Based on the texture profile analyses (TPA), it was concluded that laboratory and commercial syrups had similar textural properties with one exception. Value of stringiness of laboratory syrups was lower. This factor gave an advantage in evaluation of suitability of these products for consumers, who considered it as more comfortable in use. Rheological properties of syrups were compared by the use of Casson's model. Commercial syrups had yield stress (τ o ) in the range of 0.38–3.74 Pa, and Casson's viscosity in the range of 0.50–3.84 Pa s. Laboratory syrups had more diversified rheological properties. It was also concluded that all selected hydrocolloids (CMC, carrageenan, xanthan gum, and agar) were useful, however to different extent, for cocoa syrups production.

Effects of selected properties of ultrafiltered spray-dried milk powders on some properties of chocolate

Abstract The effects of selected properties of spray-dried milk fat powders on chocolate were determined. Milk powders produced from control or ultrafiltered (UF) milks with various levels of fat were blended with skim milk powder to give a standard 26 g fat 100 g−1 powder. Particle size of the chocolate mixes after refining decreased as the fat content and free-fat content of the powders increased. Despite this, increasing fat and free-fat contents of powders reduced the Casson viscosity of the subsequent molten chocolates. Casson viscosities using powders from control or UF milks were similar, but decreased as the particle size of powders increased and particle size after refining the chocolate mix decreased. Casson yield value and hardness decreased as fat content of powders increased. Casson yield value increased with vacuole volume of powders. It is possible to alter important properties of chocolates using milk powders of varying fat contents, free-fat contents and particle sizes.