Mechanical properties of fat-based semi solid heterogeneous materials (original) (raw)
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Rheology and Mechanical Properties of Fats
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Rheological Methods for Multiphase Materials
Relationships between structure, properties and sensory perceptions of food materials can only be achieved if the properties are measured correctly and with accuracy. Rheological properties of food materials found in the literature are sometimes contradictory and often taken with scepticism. This is particularly true for soft solid structures, which necessitate careful sample preparation, transportation to a rheometer, loading, temperature control and which often exhibit slip at the geometry wall. The use of the vane geometry for the determination of the viscoelastic properties and the yield stress is validated in conjunction with flow visualisation results. Still conventional geometries are recommended for the determination of the high shear viscosity of the soft solid materials. More work is, however, required for the understanding of the moderate shear rate behaviour close to one of the wall slip to homogeneous shear transition. This could be performed using the modified Rheoscope used in this work.
Journal of the American Oil Chemists' Society, 2013
In this study, two different groups of fat samples were prepared in a way that samples of each group had different trans fatty acid (TFA) composition but similar solid fat content (SFC). Samples of the first group (named group A) had TFA between 0.0 and 56.23 %, while the samples of the second group (group B) contained trans isomers ranging from 0.0 to 44.4 %. A polarized microscope was used to monitor the differences between the samples in terms of crystal size and crystal number during isothermal crystallization. In general, increasing TFA resulted in formation of larger crystals in a shorter time. Similar findings were also observed when small deformation time and frequency sweep experiments were conducted. A higher TFA content led to higher complex modulus values during isothermal crystallization. On the other hand, when the samples were stored at 4°C for 48 h, the samples with the lower trans isomer had higher hardness values.
Rheological Innovations for Characterizing Food Material Properties
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Advances in Food Rheology and Its Applications
Food is a very complex structured material, which is made up of water, proteins, carbohydrates, fats, and significant amount of fibers. All these constituents influence flow and structural behavior of foods significantly, and therefore, rheological properties of food are very dissimilar from the conventional polymeric materials. There are various factors that affect the stability of structured fluids. The viscosity of the liquid phase in dispersions mostly plays a major role in the flow properties of the material. Food rheology is no longer a measurement of apparent viscosity only. With time and advancement in instrumentation, food rheology today provides more in-depth information on microstructure and fluidity of a food. A transformation of measurement from a rotational viscometry to either controlled stress/strain rheometer or more advanced optimal Fourier transformation rheometry brought the accuracy, sophistication, and reliability on rheological data. There is a growing interest to understand the food microstructure and its correlation with the food textural and rheological attributes in food product development in academia and food industry. This knowledge on food rheology and microstructure helps in minimizing textural defects in the processed foods and improving consumer satisfaction. Our book "Advances in Food Rheology and Applications" is thematically divided into two broad areas: theoretical concepts and applications in the areas of food rheology. Chapters 1-10 contribute mainly in the selected theoretical aspects of food rheology, whereas Chapters 11-21 focus on practical applications of rheological concepts in gums, gels, emulsion, and selected commercial food products. Fluid and semisolid food products (eg, mayonnaise, peanut butter, chocolate, ketch up) are regularly monitored by rheological testing for the quality maintenance. Both steady and oscillatory rheological tests are used to
Journal of Texture Studies, 2015
The Foodtexture Puff Device (FPD) is a noncontact rheological measurement device, which applies an air pulse on the sample and measures the subsequent deformation of the sample surface with a laser distance sensor. The deformation behavior is considered as a measure for the rheological properties of the sample. The applicability of this device was studied for use on viscous food products with a broad range of rheological characteristics. In this study, sugar and fat-based systems with a viscosity range of respectively 0.001-6.1 Pa.s and 0.01-5.9 Pa.s were tested. Comparison of the FPD with classical rheological analyses showed that the maximum deformation created by the FPD is strongly correlated to the viscosity. Hence, the FPD is well suited for measurements on sugar-based and fatbased systems. It is capable of providing accurate, noncontact, fast, easy and nondestructive rheological measurements on food products.
Rheology for the food industry
Journal of Food Engineering, 2005
Rheological measurements are quite relevant in the food industry as a tool for physical characterization of raw material prior to processing, for intermediate products during manufacturing, and for finished foods. There are several approaches to conduct these rheological characterizations, and the selected technique pretty much depend on the specific product and the functional characteristics in need to be analyzed. Several different types of equipments are available to scientists as a tool in food rheological studies leading to acceptable results in most design situations. This paper will focus on the review and discussion of some of the most relevant rheological tests of current interest to the food industry in selected examples, i.e. gels and emulsions.
Effect of fat hardness on large deformation rheology of emulsion-filled gels
Food Hydrocolloids, 2015
The aim of this work was to investigate the impact on the texture properties of emulsion-filled gels when saturated solid fat is replaced by unsaturated liquid oil. Whey protein aggregate, gelatin and micellar casein, were chosen to form different types of gel matrices and the fat hardness was varied by selection of the fat type and variation of the temperature. As emulsifier, either whey protein aggregates, whey protein or sodium caseinate was used. Texture properties of the filled gels were investigated by uniaxial compression. The fracture properties were affected by the presence of emulsion droplets, however the effect of fat hardness was small. The presence of emulsion droplets (either liquid or solid) increases the gel stiffness as compared to the emulsion-free gel, indicating that the droplets are an active part of the gel. An increase in solid fat content led to a moderate increase in gel stiffness for whey protein aggregate gels, which was in agreement with predictions according to the Palierne model for the effect of fat hardness on the stiffness of the filled gels. For the gelatin and micellar casein gels, the magnitude by which the gel stiffness increased as a function of the solid fat content was much larger than expected on the basis of this model. Microscopical observation suggested that this was caused by an inhomogeneous distribution of the fat droplets, due to droplet aggregation or/and concentration of the droplets in gel strands, which increases the effective volume fraction of the droplets in the matrix. Food Hydrocolloids xxx (2014) 1e12 Please cite this article in press as: Oliver, L., et al., Effect of fat hardness on large deformation rheology of emulsion-filled gels, Food Hydrocolloids (2014), http://dx.Please cite this article in press as: Oliver, L., et al., Effect of fat hardness on large deformation rheology of emulsion-filled gels, Food Hydrocolloids (2014), http://dx.
Current Opinion in Colloid & Interface Science, 2011
Food rheology focuses on the flow properties of individual food components, which might already exhibit a complex rheological response function, the flow of a composite food matrix, and the influence of processing on the food structure and its properties. For processed food the composition and the addition of ingredients to obtain a certain food quality and product performance requires profound
International Journal of Food Science & Technology, 2008
Ultrasonic velocity profiling with pressure difference (UVP-PD) was demonstrated to be a successful, noninvasive, in-line measurement system for instantaneous velocity and rheological flow profiling of complex, opaque fat blends. Model systems of 25% Akomic, 75% rapeseed oil; and 25% Akomic, 74% rapeseed oil and 1% Grindsted Ò Crystalliser 110 were compared under real process conditions with UVP-PD. Results indicated that the sample containing the crystalliser had twice the viscosity of the control. These in-line results are in agreement with previous off-line results, and offer the chance to probe the mechanics of fat blend physics under real, dynamic conditions.