Physicochemical and hydration properties of different cereal and legume gluten‐free powders

International audienceBackground: The wetting and hydration stage is the key step in manufacture process of several cereal-based products. Knowledge of hydration properties of gluten-free ingredients can contribute to improve the quality of gluten-free products. The objec-tive of the present work was to investigate hydration properties for a large variety of gluten-free ingredients. Powders of tow gluten-free cereals (rice and maize) and powders of tow legumes (chickpea and faba bean) in comparison with durum wheat semolina. The hydration properties were evaluated at 25°C by vapor and liquid water addition.Results : Legume powders had the highest sorption capacity and stronger interaction with vapor water. Rice showed the highest vapor water diffusion at all RH intervals. Water holding capacity, swelling kinetics, and immersion enthalpy in liquid water were higher for legume and maize powders.Conclusion : Gluten-free cereal powders show hydration properties different from those of legumes. Different combinations of these gluten-free materials can be made to approach the properties of wheat powders

Agglomeration of a fine and hydrophobic powder by spray drying

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Modeling the mean interaction forces between powder particles. Application to silica gel-magnesium stearate mixtures.

International audienceDry coating experiments were performed by using the Hybridizer (Nara). Large host silica gel (SG) particles (d50 = 55 μm) were coated with fine invited particles of magnesium stearate (MS, d50 = 4.6 μm) for different contents of MS in the mixture. The real MS mass fraction wI obtained after mechanical treatment has been determined thanks to calibration from TGA measurements. The surface structure and morphology of MS coatings were observed using Environmental Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM) [26, 27]. AFM has been also used to measure the adhesion forces between particles. Interaction forces between the material attached to the cantilever (Magnesium Stearate MS) and the surface of the composite material (Silica Gel SG or Magnesium Stearate MS) have been determined at different surface locations. For different compositions wI of the mixture MS-SG, the numeric distribution and the mean value f of the forces fH obtained for MS-SG interactions or fI for MS-MS interactions have been established and the experimental curve showing the evolution of f versus wI has been derived. Models of ordered structures have been developed, implying morphological hypotheses concerning large spherical or cylindrical host particles H and small invited spherical I. Different types of distribution of I materials onto the surface of H have been considered: for examples a discrete monolayer –or multilayers- of monosized particles I on the H surface. The coordinence of MS particles around SG particles has been estimated to calculate the free SG surface fraction through different modelling and to obtain the mean force f versus composition wI. The theoretical force values have been compared to experimental ones. The deviations have been discussed in terms of guest particle distributions on the surface of the large host particles and morphological hypotheses

Experiment and simulation of dry particle coating

Issu de : 5th International granulation Workshop, 20-22 June 2011, Lausanne, SWITZERLANDInternational audienceThe objective of this study is to get a better understanding of dry powder coating process using experiments and numerical methods. Materials chosen as host particles are SUGLETS® (granules mainly consisting of sugar) and as invited particles, magnesium stearate (MgSt). These two materials are introduced into a high shear mixer (Cyclomix). Operations were performed at various mixing time and rotation speed of the Cyclomix. The surface morphology analysis has confirmed that Suglet particles are coated with MgSt. The product properties such as flowability, wettability and particle size distributions were also characterized. The particle motion in the Cyclomix has been simulated by using Discrete Element Method (DEM). Both number of collisions and the collision force frequency are calculated. The simulation shows an increase of the collision number with the rotational speeds. This result indicates that choosing higher rotation speeds should be better for the dry coating process as long as the particles are not broken down

Apport de l'approche numérique DEM pour la compréhension de l'évolution des propriétés physico-chimiques des particules lors de l'enrobage en voie sèche

National audienceDans cette étude, l'intérêt est porté sur l'effet des conditions opératoires sur l'enrobage en voie sèche de grosses particules " hôtes " par de fines particules " invitées " et aussi sur la modélisation de cet enrobage selon la méthode par éléments discrets (DEM) afin de mieux comprendre les phénomènes mis en jeu. Dans ce travail, les matériaux choisis comme particules hôtes sont les Suglets® (des granules sphériques constituées principalement de sucre) et les particules invitées sont en stéarate de magnésium (StMg). Ces deux éléments sont introduits en poudre dans un mélangeur de 1L à fort taux de cisaillement, le Cyclomix. Les propriétés du produit final, comme la coulabilité, la mouillabilité et le degré d'avancement du revêtement, ont été caractérisées. La variation de l'indice de coulabilité est étudiée en fonction de la durée de traitement dans le Cyclomix pour diverses vitesses de rotation, taux de remplissage et rapport de taille de particules hôte et invitée. La coulabilité des produits a été améliorée en augmentant la durée du mélange ou la vitesse de rotation, tandis que le taux de remplissage de solide ne semble pas avoir d'importance marquée. Le degré de recouvrement des particules hôtes augmente avec la durée de mélange, et la vitesse de rotation des pales. La simulation des mouvements de particules dans le mélangeur par DEM a permis d'obtenir des informations sur la position, la vitesse des particules, et d'autres paramètres énergétiques, ainsi qu'une estimation du degré de mélange à tout instant. Grâce à l'interprétation de ces mouvements de particules à l'intérieur du Cyclomix, nous pouvons expliquer les différences de comportements déduites de l'analyse des propriétés physico-chimiques (Sato et al. 2012) des produits composites obtenus. Investigations of the effect of the operation conditions on the dry coating and the motion of particles in a high shear mixer by the DEM simulation have been done. The Suglet® and the MgSt materials have been chosen as the host/invited particles, respectively. The treatment of dry coating has been carried out in the Cyclomix, high shear mixer at different rotational speeds, filling ratio of the samples and particle size ratio to observe the effect of the operation conditions on the dry coating. The properties of the products, such as the flowability, wettability and the conversion ratio have been analyzed. The flowability has been improved along with the operation time of Cyclomix. Higher speeds of rotation of the Cyclomix can improve the flowability more rapidly. However, the flowability does not seem to be sensitive to the filling ratio. To simulate the flow of host/guest particles in the mixer, the Discrete Element Method (DEM) was applied. Experimental results such as flowability and wettability can be explained with particles flows evolutions inside the Cyclomix with different rotational speed

Experiment and simulation of the dry particle coating

International audienceThe objective of this study is to get a better understanding of dry powder coating process using experiments and numerical method. Materials chosen as host particles are SUGLETS® (spherical granules mainly consisting of sugar) and as invited particles, magnesium stearate (MgSt). These two materials are introduced in the Cyclomix high shear mixer. Operations were performed at various mixing time and rotation speed of the Cyclomix. The surface morphology analysis has confirmed that Suglet particles are coated by MgSt. The product properties such as flowability, wettability and particle size distributions were also characterized. The particle motion in the Cyclomix has been simulated by using Discrete Element Method (DEM). Both number of collisions and the collision force frequency are calculated. The simulation shows an increase of the collision number with the rotational speeds. This result indicates that the higher rotation speed should be better for the dry coating process as long as the particles aren't broken down

Effect of Mechanical dry Coating on the Flowability and the Wettability of Silica Gel Powder

National audienceDry particle coating has been used to create new-generation materials by combining different powders exhibiting different physical and/or chemical properties. Particles with relatively large particle size (host particles, 1-500 µm) can be mechanically coated with fine particles (guest particles, 0,1-50 µm) in order to create new functionality or to improve their initial characteristics. In this study the dry coating experiments were performed with two different mixing processes using Hybridizer (Nara) and Cyclomix (Hosokawa). Silica gel particles (d50 = 55 µm) were coated with fine particles of magnesium stearate (d50 = 4,6 µm) at two different mass ratios of magnesium stearate, 5% and 15%. Several methods of characterization were used to study the effect of dry coating on the flowability and the wettability of silica gel powder. The uncoated and coated silica gel particles were observed by environmental scanning electron microscopy (ESEM). The images showed that a more uniform coating was obtained in the case of Hybridizer. The flowability of the different samples obtained with Hybridizer and Cyclomix was characterized by measurements of the tapped and aerated densities. It has been shown that the flowability of silica gel treated in Hybridizer was not significantly affected whereas the flowability was reduced after treatment in the Cyclomix. The wettability of silica gel powder was determined by measurements of the contact angle between the water drop and the powder bed prepared for each sample. The results obtained showed that the coating of silica gel powder by hydrophobic magnesium stearate in both the Hybridizer and Cyclomix, improves its moisture resistance

Production de particules composites par enrobage en voie sèche dans un mélangeur cyclomix et modélisation DEM

National audienceUne modélisation de l'enrobage en voie sèche selon la méthode par éléments discrets (DEM) a été développée afin de mieux comprendre les phénomènes mis en jeu. Dans ce procédé, des poudres de taille relativement grande (dites " hôtes ") sont recouvertes de particules fines (dites " invitées ") par l'application de forces mécaniques sans l'aide de solvants ni de liants hydrauliques. Dans ce travail, les matériaux choisis comme particules hôtes sont les Suglets® (des granules sphériques constituées principalement de sucre) et les particules invitées sont constituées de stéarate de magnésium (MgSt). Ces deux éléments sont introduits sous forme de poudre dans un mélangeur à fort cisaillement appelé Cyclomix. Les propriétés du produit final comme la coulabilité et la fraction massique ont été caractérisées. La variation de l'indice de coulabilité en fonction de la durée de traitement par Cyclomix pour 4 vitesses de rotation et 3 taux de remplissage différents. La coulabilité des produits a été améliorée avec une augmentation de la durée d'opération et de la vitesse de rotation. Mais le taux de remplissage ne semble pas influer sur l' amélioration de la coulabilité. Le rendement en produit, estimé par sa fraction massique, est analysé. La constante de taux d'enrobage est corrélée avec la distance de rotation obtenue par DEM. Il a été montré que l'efficacité d'enrobage peut être prévue par la simulation

Dry coating in a high shear mixer: Comparison of experimental results with dem analysis of particle motions

International audienceExperimental dry coating of guest particles on the surface of host particles is performed by mechanical forces in a high shear mixer called "Cyclomix". The studied system (a mixture of particles of sugar, "Suglet™" as host particles and magnesium stearate as guest particles) was chosen as a model one to achieve better understandings of the phenomena during mixing. To simulate the flow of host/guest particles in the mixer, the Discrete Element Method (DEM) was applied. Experimental results such as flowability and wettability can be explained by particles flows evolutions with different rotational speed or duration treatment inside the Cyclomix

Effect of operating conditions on dry particle coating in a high shear mixer

International audienceAn investigation into the effects of the operating conditions on a dry particle coating process has been performed with mixtures of sugar grains (Suglet®) and magnesium stearate (MgSt) as the host and invited particles, respectively. Dry coating has been carried out in a high shear mixer (Cyclomix®) at different processing times t, rotational speeds ω, and filling ratios J, of the mixer. In order to determine the effect of the operating conditions on the properties of the products, the changes in flowability and wettability of the mixtures as a function of ω, J and the operating time t have been analyzed. The flowability is found to be improved by longer processing times. Higher speeds of rotations can improve the flowability more rapidly. However, the flowability does not seem to be sensitive to the filling ratio and it may be concluded that operating with higher filling ratios gives higher production. A method is proposed to measure the mass fraction of invited particles on the surfaces of the host particles. This fraction is linked to the product properties as the flowability and wettability. This result can be predicted by a model using a coating rate constant kc which can be used to optimize dry coating processes to give desired properties of coated particles. This coating rate constant can define and represent the efficiency of the dry coating