Rheological and mechanical characterization of wet agglomerates processed in low shear mixer

The mechanical and rheological characterization of structures processed by wet agglomeration is a way to study their structural organization. The aim of this study is to submit and discuss the results of mechanical and rheological characterization of wet agglomerates obtained by wetting cereal powder in low shear mixer. For various conditions of wetting, these properties are obtained thanks to shearing and compression tests led on a powder rheometer (FT4 - Freeman Technology, UK). The analysis of the mechanical and rheological properties of agglomerates obtained after wet agglomeration process has been carried out thanks to an approach based on soil science and granular media. This approach makes it possible to highlight the great influence of water content on the rheological behavior of the agglomerates bed bulk: Its increase results in variations of the friction between grains together with variations in their cohesion. These variations are analyzed regarding the modifications in the population balance induced by the increase in water content. Uniaxial compression tests make it possible to calculate, through three compression models (Kawakita, Hackel and Adams), the agglomerates strength. It is shown that it evolves according to a decreasing power law when water content increases. These results are in accordance with the fractal description of the agglomeration process that support a decrease of the agglomerates solid volume fraction, and thus of their resistance, with water content. (c) 2013 Elsevier Ltd. All rights reserved

Agglomeration of wheat powders by a novel reverse wet agglomeration process

The wet agglomeration process is implemented to improve the powders functionalities. The objective of the present work is to investigate a novel reverse wet agglomeration process for reactive powders. This novel process is conducted in two main successive phases during mechanical mixing. The first phase consists of mixing a specific amount of powder and water to produce a continuous saturated paste, called dough, by controlling the physicochemical reactivity of the biochemical components of the powder. The second stage consists of generating the agglomerates by adding the powder inside the continuous dough under mixing conditions. This agglomeration process is mainly promoted by fragmentation mechanism. We have evaluated the impact of the process conditions on the electric consumption, agglomeration yield and characteristics of the agglomerates. Experiments were conducted using durum wheat semolina as raw materials. The results were compared to those obtained by using the classical wet agglomeration process, at same final water content of the agglomerates

Diagnostic de l'allergie alimentaire à la noisette chez l'enfant : il faut rester prudent !

Diagnosing of hazelnut allergy was recently enhanced by value of serum specific IgE versus recombinant fractions, Cor a 1 and Cor a 8. Their positivity could be linked with clinical benignity for Cor a 1 and severity for Cor a 8. The authors report four cases contradicting this aphorism. The oral food challenge to hazelnut induced in these patients a severe clinical response with a severe increase of serum tryptase at the end of the challenge. The level of serum specific IgE to Cor a 8 was negative (or very low). For Cor a 1 the level was very high or low. We discuss the clinical relevance of the aphorism "Cor a 1 = benignity; Cor a 8 = severity", which use should be modulated in clinical practice. Other allergenic fractions could account for these cases. (c) 2012 Elsevier Masson SAS. All rights reserved

Can we predict the microstructure of a non-woven flax/PLA composite through assessment of anisotropy in tensile properties?

Flax/Poly-(lactide) non-woven composites are an alternative to conventional glass/poly-(propylene), offering a potentially lower environmental impact solution for the automotive industry. To understand this complex material, its detailed architecture and void distribution are examined through 3D microtomography. Anisotropy in fibre orientation is also observed, further verified through off-axis tensile tests. Then micro-mechanics and laminate theory are used, taking into account fibre orientation distribution, to predict mechanical properties and compare with experimental measurements. Even though some deviation is observed at off-axis angles greater than 45°, we report that off-axis tensile tests (property) can be used to predict fibre orientation (structure) in industrial production facilities as a simple means of quality control and tailored design of new non-woven preforms.Authors thank Interreg V.A Cross-Channel Programme for funding this work through our project, FLOWER (Grant number: 23; http://flower-project.eu)

Power consumption profile analysis during wet agglomeration process: Energy approach of wheat powder agglomeration

Mechanical energy input during mixing is one of the key stages of the mixer agglomeration process. It allows the distribution of water over the powder, the formation and growth of agglomerates, and homogenization of the agglomerate properties. The objective of the present work is to determine the power consumed by the wet agglomeration process of a reactive granular material, in the specific case of agglomeration of durum wheat semolina under the conditions of couscous grain production. Our study attempts to investigate the effects of process conditions (i.e. blade rotation speed, mass load, and water addition level) on the distribution of the different energy costs consumed by the mixer during the wet agglomeration process. As a baseline, we first measured the energy consumption by the motor for no-load mixing. To evaluate the energy consumption to transport inert load, we measured the energy consumption by the motor after introduction of different masses of durum wheat semolina without adding water. Finally, we study the energy consumption of the agglomeration process during mixing after water addition. Results demonstrate that the energy specifically consumed for agglomeration process increases with water content, from 9% (at 22% water content) to 26.6% (at 42% water content). However, the energy necessary to form and structure the agglomerates only represent at the maximum one third of the total energy consumed by the equipment. (C) 2012 Elsevier BM. All rights reserved

Study of agglomeration mechanisms of food powders: application to durum wheat semolina

Contacts: fax: +33 4 9961 3076. E-mail address: [email protected] wet agglomeration of durum wheat semolina is an important stage in couscous production which contributes to the final quality of the end products (couscous grains). There is still a lack of studies in investigating the agglomeration mechanisms of durum wheat semolina. The present study aims to investigate the agglomeration mechanisms occurring during the wetting/mixing process of durum wheat semolina. This process implies the mixing of semolina with different quantities of water in low shear mixers at fixed operating speed. The wet agglomeration mechanisms promote significant changes in size and textural parameters that have been investigated. The evolution in the diameter of the agglomerated structures (nuclei, agglomerates and dough pieces) composing the bed bulk, shows a continuous growth process associated to the expansion of their internal structure. Descriptions of the internal and the external structures of these elements are investigated by scanning electron microscopy. The evolution of solid volume fraction is depicted with respect to the water content at both bed bulk scale and agglomerate scale. At the bed bulk scale, a three-stage texturing phenomenon is identified. At the agglomerate scale, the evolution of solid volume fraction can be related to the evolution of the agglomerate size. The relation between the diameter and the solid volume fraction of the agglomerates can be modeled by a power law equation and could thus indicate that the agglomeration mechanism of durum wheat semolina is a fractal formation proces