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Compression cycle schematic. P, load; P m , maximum load; W P , plastic work dissipated (W T = W E + W P ); W E , work performed during unloading; and h, deformation.
Source publication
The method to measure hardness and other viscoelastic properties of intact wheat kernels is presented. Wheat with 9.3% moisture showed high elastic behavior compared with wheat tempered at 22.5% moisture that showed a plastic behavior. Load-deformation curves showed that bread wheat behaves as a more plastic material than durum wheat, which is a mo...
Contexts in source publication
Context 1
... L 0 and L f are the initial kernel height and final deformation, respectively. The viscoelastic behavior of the wheat kernels was calculated using compression experiments, the work-of-compression was determined from the loading/unloading curve (Fig. 1). The area under the loading curve gives the total work done (W T , ) by the loading device during compression. The reversible elastic contribution (W E , ) of the total work can be deduced from the area under the unloading curve, and the energy absorbed by plastic deformation alone is the difference between the two (W P = W T -W E ...
Context 2
... test methods include the use of a parallel plate for whole grain, with a spherical indenter and a cylindrical indenter, and a parallel plate on core specimens. Despite successive improvements, the methods based on the Hertz and Boussineseq theory all have problems due to the whole structure of the wheat grain (Haddad et al 1998). Any variability in the form of the grain or the properties induces errors in the measurement of the viscoelastic characteristics of the endosperm ( Haddad et al 1998). ...
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Citations
... This trend aligns with the findings of Figueroa et al. (2011), who similarly noted a decrease in Young's modulus from 132.0 to 29.7 MPa as MC increased from 12.7 to 20.7%, employing the same compression method. However, Ponce-García et al. (2008) reported higher values for modulus (394.8-99.2 MPa) for MC ranging from 9.3 to 22.5%. ...
... MC rendered particles more compliant and ductile, requiring less force to reach rupture due to their lower Young's modulus, resulting in higher compressibility and lower stiffness. The rupture forces were comparable to those reported by Bhise et al. (2014), ranging from 57.3 to 37.0 N for MC of 12 and 18%, respectively, and from 58.1 to 23.2 N for MC ranging from 9.3 to 22.5%, as reported by Ponce-García et al. (2008). These values were lower than those reported by Gorji et al. (2010), which ranged from 162.6 to 72.7 N for MC from 7.8 to 20%. ...
In this study, the Discrete Element Method (DEM) was employed as a computational approach to analyse the bulk behaviour of wheat (Triticum aestivum L., cv. 'Pionier') under compressive loading. A laboratory compression apparatus was utilised as a basis for the acquisition of data from compression tests. To ensure accurate DEM predictions, the physical, mechanical, and interaction properties of wheat kernels were experimentally determined for two different moisture contents (12.4% and 25.4% w.b.). Five particle models were constructed to represent the geometric shape of the kernel, with the model composed of five sub-spheres identified as the most suitable, ensuring an optimal balance between computational complexity and simulation accuracy. The bulk compression results from DEM simulations were compared to experimental data, revealing a good agreement for volumetric strain, bulk density increase, and bulk compressibility within the specified range of applicability. Simulations provided valuable insights into temporal and spatial variations of forces and deformations acting on individual particles, thereby enhancing the understanding of bulk behaviour at different compression levels. The moisture content was found to significantly affect the particle compressive forces, deformation capabilities, and bulk compression characteristics. In conclusion, this study demonstrated the great potential of DEM in predicting the bulk behaviour of wheat under compression, providing valuable information for practical storage and handling processes.
... Te diferences in physical properties of grains were analyzed by compression or shear tests combined with mechanical indexes such as grain elastic modulus, shear modulus, and loss modulus [59]. In addition to these studies on the viscoelasticity of starch gel or dough, there is also a certain relationship between the rupture behavior of grains and their viscoelasticity [60,61]. Te maximum rupture force of wheat and rye showed a strong correlation with their viscoelasticity. ...
Grain is extremely vulnerable to external loads during production and processing, resulting in the deterioration of grain quality. Deteriorated grain not only affects the economic value of grain but also affects the safety of storage. This has a very important relationship with the biomechanical properties of grains. It is of great significance to explore the mechanical properties of grain under different conditions and analyze the relationship between its physical and chemical properties and mechanical properties for improving its processing and eating quality. In this paper, the research methods of the mechanical properties of grains are reviewed. Various factors influencing the mechanical properties of cereals were analyzed. The relationship between the internal organizational structure of grain and its mechanical properties was discussed. This paper puts forward the shortcomings in the current research on the mechanical properties of grains and puts forward the prospect and analysis of its importance in future development in order to provide a reference for reducing crushing in the grain processing process.
... The grain moisture content, which also has a substantial impact on the physical properties linked to volumetric grain weight and bulk density, alters the surface characteristics of seed coat and kernel endosperm. Following their investigation on how moisture content affected several physical traits of wheat kernels, researchers came to the following conclusions: with increasing moisture content, thousand kernel weight, axial dimensions, kernel volume, porosity, and sphericity all increase, but bulk density decreases (Tabatabaeefar, 2003;Ponce-García et al., 2008;Karimi et al., 2009;Bhise et al., 2014). Since higher grain moisture content makes grains more prone to deformation, physical characteristics of cereal change with change in grain moisture content (Molenda and Horabik, 2005). ...
Wheat is the most widely grown crop in temperate countries, and it is consumed as a human food and livestock feed. Whole wheat is composed of bran, germ, and endosperm. The wheat milling separates the wheat grain into germ, bran, and endosperm, and the efficiency of separation depends on the milling process. Various characteristics of wheat grain, namely, shape, size, texture, density, and chemical content, are known to affect the milling process. Different milling methods such as stone milling, roller milling, jet milling, ultrafine milling, and hammer milling are being employed for wheat milling. During conventional milling, only carbohydrate-rich endosperm is retained, and other important nutrients and phytochemicals are lost with the removal of bran and germ. The resulting refined wheat flour is used for the preparation of bakery and other food products, which are liked by the consumers due to taste, texture, and appearance. But the consumption of refined wheat flour is known to be associated with the widespread prevalence of digestive disturbances and nutritional disorders. Therefore, milling is considered a crucial process that influences the nutritional quality of wheat-derived food products. Consumers nowadays demand whole wheat grain products because of health benefits associated with their consumption. The growing demand for whole-wheat flour (WWF) has triggered researchers to explore the impact of different types of milling and processing technologies on the nutritional quality of resultant wheat flour. Despite the increased demand for WWF, proper milling processes for its production are yet to be established. Thus, in this chapter, an attempt is made to discuss in detail different milling technologies and their effect on the nutritional quality of wheat flour. Further, challenges and strategies to produce wheat flour for the development of specific end products with desired nutritional and functional properties will be discussed.
... However, very little work has been dedicated to examining the relationship between the biophysical and viscoelastic properties of intact wheat kernels [2]. Ponce-García et al. [8] reported a simple and practical method for evaluating the fundamental mechanical properties of intact wheat kernels without any preparation to increase the selection efficiency for processing, marketing, and end-use. The size, shape, weight, density, and volume of kernels used as the raw material for processing have a significant relationship with several technological requirements. ...
... Twenty kernels from each sample were randomly selected for each cereal type at the two moisture contents (12% and 16%, w/w). The elastic modulus (E) was obtained at 5% deformation [8]. The total work (W t ), elastic work (W e ), and plastic work (W p ) were calculated from the load-unload curves obtained after compression from the texture analyzer based on the methods proposed by Ponce-García et al. [8] and Gubicza et al. [26]. ...
... The elastic modulus (E) was obtained at 5% deformation [8]. The total work (W t ), elastic work (W e ), and plastic work (W p ) were calculated from the load-unload curves obtained after compression from the texture analyzer based on the methods proposed by Ponce-García et al. [8] and Gubicza et al. [26]. The degree of elasticity (D e ) and resilience (R) were calculated according to the method of Figueroa et al. [2]. ...
The viscoelastic properties of cereal kernels are strongly related to their quality, which can be applied to the development of a more selective and objective classification process. In this study, the association between the biophysical and viscoelastic properties of wheat, rye, and triticale kernels was investigated at different moisture contents (12% and 16%). A uniaxial compression test was performed under a small strain (5%), and the increase in viscoelasticity at 16% moisture content corresponded to proportional increases in biophysical properties such as the appearance and geometry. The biophysical and viscoelastic behaviors of triticale were between those of wheat and rye. A multivariate analysis showed that the appearance and geometric properties significantly influenced kernel features. The maximum force showed strong correlations with all viscoelastic properties, and it can be used to distinguish between cereal types and moisture contents. A principal component analysis was performed to discriminate the effect of the moisture content on different types of cereals and to evaluate the biophysical and viscoelastic properties. The uniaxial compression test under a small strain and the multivariate analysis can be considered a simple and non-destructive tool for assessing the quality of intact cereal kernels.
... The elastic behavior of intact kernels was related to the sedimentation volume and composition of glutenin. He demonstrated that hard wheats showed higher plastic deformation work than durum wheat kernels, and therefore had higher elastic properties [44]. Some relationships between wheat hardness and Zeleny index and protein quality were observed in [45]. ...
The aim of the study was to examine the Peleg and Normand model to characterize
the overall stress relaxation behavior of wheat kernel at varying load conditions. The relaxation
experiments were made with the help of the universal testing machine, Zwick Z020, by subjecting
the samples to compression at four distinct initial load levels, i.e., 20 N, 30 N, 40 N, and 50 N. The
measurements were made for four wheat varieties (two soft and two hard-type endosperms) and
seven levels of moisture content. Relaxation characteristics were approximated with the help of
the Peleg and Normand equation. An interactive influence of the load level, moisture, and wheat
hardness on the Peleg and Normand constants has been confirmed. For moist kernels, a higher
amount of absorbed compression energy was released, since less energy was required to keep the
deformation at a constant level. The constants di�ered depending on wheat hardness. Higher values
of k1 revealed that the initial force decay was slower for hard varieties. This is more characteristic
of elastic behavior. Similarly, higher values of k2 pointed to a larger amount of elastic (recoverable)
energy at the end of the relaxation. The initial loading level had no or only a slight e�ect on the model
coe�cients (Y(t), k1, and k2). The parameters of the Peleg and Normand model decreased with an
increase in the water content in the kernels
... The elastic behavior of intact kernels was related to the sedimentation volume and composition of glutenin. He demonstrated that hard wheats showed higher plastic deformation work than durum wheat kernels, and therefore had higher elastic properties [44]. Some relationships between wheat hardness and Zeleny index and protein quality were observed in [45]. ...
The aim of the study was to examine the Peleg and Normand model to characterize the overall stress relaxation behavior of wheat kernel at varying load conditions. The relaxation experiments were made with the help of the universal testing machine, Zwick Z020, by subjecting the samples to compression at four distinct initial load levels, i.e., 20 N, 30 N, 40 N, and 50 N. The measurements were made for four wheat varieties (two soft and two hard-type endosperms) and seven levels of moisture content. Relaxation characteristics were approximated with the help of the Peleg and Normand equation. An interactive influence of the load level, moisture, and wheat hardness on the Peleg and Normand constants has been confirmed. For moist kernels, a higher amount of absorbed compression energy was released, since less energy was required to keep the deformation at a constant level. The constants differed depending on wheat hardness. Higher values of k1 revealed that the initial force decay was slower for hard varieties. This is more characteristic of elastic behavior. Similarly, higher values of k2 pointed to a larger amount of elastic (recoverable) energy at the end of the relaxation. The initial loading level had no or only a slight effect on the model coefficients (Y(t), k1, and k2). The parameters of the Peleg and Normand model decreased with an increase in the water content in the kernels.
... Finally, it is important to highlight that grain moisture content has deep influence on the physical properties, particularly those related with volumetric grain weight and density in bulk as it modifies surface properties of seed-coat as well as the properties of kernel endosperm. Several studies [34,42,43,47] have reported the effect of moisture content on different wheat kernel physical properties and concluded that increasing of moisture content level increased axial dimensions, thousand kernel weight, porosity, kernel volume and sphericity, while bulk density decreased. Higher grain moisture content results in an increase in susceptibility of grains to deformation, thus physical properties of cereal grains vary as a function of moisture content [13,44]. ...
Cereal grains are biological materials and as such have certain unique characteristics greatly affected by both genetics and environment. Wheat is worldwide considered as the main cereal grain in the average human diet. The aim of this chapter is to provide an overview of the most important grading factors and kernel physical parameters that are involved in the estimation of quality specifications. The determination of the physical properties of wheat kernels gives a first approximation of the structural characteristics useful for the design and selection of equipment for handling, harvesting, aeration, drying, storing and more importantly to functionality, processing and end uses. For instance, physical quality test that directly measure those properties are needed. To get a better prediction, physical evaluation of the wheat kernels offers a first and interesting quality control for their selection as raw materials in order to optimize quality of a large diversity of products. Kernel colour, shape, size, sphericity, porosity and bulk and specific densities and damages incurred due to heat, insects, molds or sprouting are relevant tests related to wheat kernel properties and quality.
... The latter conducted several investigations that focused on developing methods and evaluation techniques to increase the efficiency of the selection, processing, merchandising and end use of grains [6]. The study of the mechanical properties of wheat grains offers acceptable quality criteria during the milling process, specifically the conditioning parameters, the optimization of energy consumption and the quality of the produced flour. ...
... Starting from this point, Khazaei and Mann [27] established that the relaxation time determines how the material dissipates the stress after a rapid and sudden deformation was applied such that the result of the relaxation test could be useful in estimating the susceptibility of materials to damage. The evaluation of mechanical properties in grains is particularly difficult because these parameters may be seriously affected by the percentage of strain, temperature and moisture content [6]. ...
... Ponce-García et al. [6] proposed and validated an innovative method of using the compression load to evaluate the viscoelastic properties by using intact soft, hard and durum wheat kernels at different moisture levels. The viscoelastic behavior of the wheat kernels was calculated using compression experiments. ...
Abstract
To assess the quality of food grains, it is necessary to consider the following two aspects: their general characteristics and their intrinsic quality. Analyzing the quality of wheat kernels is complex due to the particularity of wheat proteins and the diversity of products that can be developed. In contrast, basic factors are used to assess quality aspects, with a focus on kernel hardness. This parameter is usually measured by the force that is required to make the grain rupture. The application of force must be controlled, and hence, the grain will exhibit other mechanical attributes and behavio‐ ral characteristics that can be used to evaluate it more objectively. This has led to the development of nondestructive evaluation methods based on the mechanical proper‐ ties of kernels. This review carried out research on grain wheat, in which the main objective was to evaluate mechanical properties, including the viscoelasticity of the wheat kernels, by using compression tests. The study examined different methods of applying those techniques and the parameters they evaluated. Finally, the results obtained by the different investigation groups that applied the compression tests on wheat kernels were discussed.
... The rheological behavior of individual wheat kernels includes various parameters, such as viscoelasticity (total, elastic and plastic work) and stress relaxation. [1][2][3] Furthermore, the industrial quality of wheat is related to the viscoelastic properties of the kernel; these properties affect the milling and baking quality. In addition, the moisture content in a wheat kernel has a significant effect on its rheological properties. ...
BACKGROUND: The aim of this research was to evaluate the viscoelastic properties of conditioned wheat kernels and their doughs by applying the compression test under a small strain. Conditioned wheat kernels and their doughs, from soft and hard wheat classes were evaluated for total work (W t), elastic work (W e) and plastic work (W p). RESULTS: Soft wheat kernels showed lower W e than W p , while the hard wheat kernels had a W e that was higher than W p. Regarding dough viscoelasticity, cultivars from soft and hard wheat showed higher W p than W e. The degree of elasticity (DE%) of the conditioned wheat kernel related to its dough decreased ~46% in both wheat classes. The W t , W e and W p from the soft wheat kernel and dough correlated with physicochemical and farinographic flour tests. The W t , W p and the maximum compression force (F max) of the dough from hard wheat class presented highly significant negative correlations with wet gluten. CONCLUSION: The viscoelasticity parameters from compression test presented significant differences among conditioned wheat classes and their doughs.
... The rheological behavior of individual wheat kernels includes various parameters, such as viscoelasticity (total, elastic and plastic work) and stress relaxation. [1][2][3] Furthermore, the industrial quality of wheat is related to the viscoelastic properties of the kernel; these properties affect the milling and baking quality. In addition, the moisture content in a wheat kernel has a significant effect on its rheological properties. ...
Background:
The aim of this research was to evaluate the viscoelastic properties of conditioned wheat kernels and their doughs by applying the compression test under a small strain. Conditioned wheat kernels and their doughs, from soft and hard wheat classes were evaluated for total work (Wt ), elastic work (We ) and plastic work (Wp ).
Results:
Soft wheat kernels showed lower We than Wp , while the hard wheat kernels had a We that was higher than Wp . Regarding dough viscoelasticity, cultivars from soft and hard wheat showed higher Wp than We . The degree of elasticity (DE%) of the conditioned wheat kernel related to its dough decreased ~46% in both wheat classes. The Wt , We and Wp from the soft wheat kernel and dough correlated with physicochemical and farinographic flour tests. The Wt , Wp and the maximum compression force (Fmax ) of the dough from hard wheat class presented highly significant negative correlations with wet gluten.
Conclusion:
The viscoelasticity parameters from compression test presented significant differences among conditioned wheat classes and their doughs.
