Joël Abecassis

Hydration properties of durum wheat semolina: influence of particle size and temperature

The hydration of semolina particles is an essential step in couscous processing which leads to binding between particles for the formation of agglomerates. Despite this importance, the hydration properties of such food products are rarely studied and in particular, durum wheat semolina has never been investigated. Here we present,a study of the hydration properties of durum wheat semolina by determination of water sorption isotherms, and other characterisation techniques to obtain a better understanding of hydration mechanisms. Equilibrium and dynamic sorption properties, have been measured as a function of relative humidity by means of a controlled atmosphere microbalance. It is found that durum wheat semolina presents a type II isotherm [F. Rouquerol, J. Rouquerol, K. Sing, Adsorption by Powders and Porous Solids-Principles Methodology and Applications, Academic Press, 1999] indicative of multi-layer adsorption. The Guggenheim-Anderson-de Boer (GAB) model is used to describe the isotherm and obtain a better understanding of hydration mechanisms and liquid/solid interactions. The effects observed are related to physical properties of the semolina. In particular, the size of the semolina particles is found mainly to influence sorption kinetics: the finer the particles, the faster their sorption kinetics. Increasing temperature in the range 25-45 degreesC accelerates sorption kinetics. Furthermore, hydration causes no irreversible transformation of semolina components. Thus, absorption kinetics seem to be influenced by physical mechanisms, while the biochemical composition determines the amount of water sorbed.

Mechanical Properties of Wheat Seed Coats

ABSTRACT The crumbliness of starchy endosperm and the resistance of bran are key characteristics that enhance milling behavior of wheat and are dependent on the genetic origin and moisture content of the grain. A method was developed to measure the mechanical properties of bran samples based on the measurement of tensile stress and strain. Tests conducted with this highly reproducible and sensitive method documented cultivar and moisture-content effects (6.3, 13.8, and 18%, wb) on rheological behavior of wheat seed coats. A moisture-dependent reduction in stress to fracture (-15 to -30%) and in Youngs modulus (-45 to -55%) was quantified. An increase in deformation to fracture of seed coats was also correlated with bran size differences after milling. The energy required to fracture a sample (from 0.4 to 1.3 J/mm3) was considered the most valid of all presented parameters for assessing the milling behavior of wheat seed coats and the size of bran fractions.

Mechanical and Physicochemical Characterization of Vitreous and Mealy Durum Wheat Endosperm

ABSTRACT The mechanical, physical, and biochemical characteristics of mealy and vitreous endosperm were investigated. Endosperm were obtained from four durum wheat cultivars grown under different nitrogen fertilization designs. The textural properties and the density of the endosperm were measured on hand-shaped parallelepiped endosperm samples. Endosperm protein content and composition and also gliadin composition were investigated by HPLC. Mechanical tests showed that mealy and vitreous endosperm differed in hardness and vitreousness. Vitreousness increased with nitrogen fertilization supply whereas there was no variation among the different cultivars. Hardness seemed to be linked to genotype and insensitive to nitrogen supply. From this result, we concluded that hardness and vitreousness are not related. Endosperm protein content and gliadin-to-glutenin ratio were related to nitrogen supply and increased especially when nitrogen supply was applied at flowering. At the same time, endosperm vitreousness ...

Description of a micromill with instrumentation for measuring grinding characteristics of wheat grain.

ABSTRACT A new method for characterizing the grinding characteristics of wheat grain is described. A micromill was designed for this purpose and equipped with on-line torque transducers to obtain accurate measurements of mechanical energy consumption during milling. This micromill can be used for testing the milling performance of small quantities of grain (100 g). It can distinguish between different types of wheat grain (soft wheat, hard wheat, durum wheat) on the basis of total specific energy during milling. Wheat characterization can be enhanced by taking particle sizes of the milled products into account. A milling index based on energy consumption and particle size reduction was developed to characterize wheat behavior during milling. This index had a high discriminatory potential, ranging from 100 kJ/kg for soft wheat flour to 600 kJ/kg for durum wheat flour. This micromill directly measures the grinding resistance of wheat kernels as a function of both the kernel hardness and vitreousness, contra...

A rapid general method for appraising the rheological properties of the starchy endosperm of cereal grains

ABSTRACT A rapid, simple method was developed to prepare small, parallelepipedal test samples of endosperm of wheat, corn, and rice grains. Compression tests performed on endosperm samples revealed the following mechanical properties: modulus of elasticity (E, GPa), breaking stress (σrup, MPa), and maximum breaking strain (erup, %). All tests were performed on several endosperm test samples of each cereal species. The results displayed good repeatability and several significant differences in the mechanical behavior of different endosperm structures, especially among soft, hard, and durum wheats. Rice and corn endosperm displayed mechanical behavior similar to that of durum wheat endosperm. The method proposed appears to be sufficiently sensitive and repeatable for studying the incidence of hardness and vitreousness of cereal grain endosperm in relation to its suitability for milling.

Production of Starch with Very Low Protein Content from Soft and Hard Wheat Flours by Jet Milling and Air Classification

ABSTRACT Jet milling is a fluid energy impact-milling technique generally used for the ultrafine reduction of higher value materials. The efficiency of jet milling combined with air classification appears very efficient to separate starch from other wheat flour aggregate components and to produce wheat starch with very low residual protein content. Indeed, residual protein content of the starch-rich fraction can be reduced to <2% db with a series of successive grinding and air classification operations. Lipid and pentosan contents were also reduced in the starch-rich fraction. Nevertheless, jet milling cannot eliminate grinding differences observed between different types of wheat. Wheat hardness continues to have an effect on milling and classification yields and on the composition of air classification fractions. To obtain starch-rich fraction with only 2% protein content, hard wheat flour required a series of at least five grinding steps, whereas only three steps are necessary for soft wheat flour. Und...

An artificial intelligence-based approach to deal with argumentation applied to food quality in a public health policy

Argumentation is a relatively new research area in Artificial Intelligence. Since the early 1980s, its use has been investigated in various frameworks. We propose a general model for recommendation-based argumentation by extending Dungs seminal argumentation system. This approach is applied to analyse argumentation on food quality in a public health policy. Cereal products, and more specifically bread, are used by decision makers as a healthy lever to fight against diseases such as obesity or diabetes. Our model outputs new recommendations based on stakeholders argumentation by targeting some specific audiences.

Influence of UV Exposure on Phenolic Acid Content, Mechanical Properties of Bran, and Milling Behavior of Durum Wheat (Triticum Durum Desf.)

ABSTRACT Durum wheat bran was exposed to UV radiation up to 48 hr and the changes in ferulic acid (FA) content in the peripheral part s of grain were measured. The treatment resulted in a 25% decrease in FA monomer and a 44% decrease in dehydrodiferulic acid (DHD) ester-linked to the cell-wall arabinoxylans. This reduction was partly explained by a significant increase of FA (30%) and DHD (36%) engaged in hot alkali-labile linkages. The results suggest that UV irradiation induced the formation of new cross-links between feruloylated arabinoxylan and lignin in the pericarp. The effects of UV treatment on bran mechanical properties and wheat milling behavior were investigated. UV irradiation for 15 hr increased the stress to rupture by 30% and decreased the extensibility of bran tissues by 54%. This stiffening was associated with an increase in bran friability during grinding. Although this effect was due in part to the hydrothermal history of the grain, chemical modification induced by UV significantly inf...

Effects of Physicochemical Characteristics and Lipid Distribution in Algerian Durum Wheat Semolinas on the Technological Quality of Couscous

ABSTRACT Semolinas milled from 18 Algerian durum wheat cultivars cropped over a two-year period (1999-2000) were used for making couscous. This study was designed to determine the impact of lipid components of durum wheat semolina on the quality of the couscous end product. Lipids were extracted from semolina by various techniques and classified as free or bound lipids, polar or apolar lipids, and glycolipids or phospholipids. An analysis of the overall results clearly revealed that the cooking quality of couscous made from different durum wheat semolinas was partially dependent on the semolina free lipid content and composition. We have shown that this is mainly a varietal characteristic (53.4%). The surface state of the couscous, i.e., caking index (r = -0.48) and cooking loss (r = -0.54), thus depends on the apolar lipid content. Polar lipids, and especially glycolipids, affect couscous texture in terms of firmness (r = 0.57 and r = 0.63, respectively). Polar bound lipids also contribute to couscous sw...

An iterative approach to build relevant ontology-aware data-driven models

In many fields involving complex environments or living organisms, data-driven models are useful to make simulations in order to extrapolate costly experiments and to design decision-support tools. Learning methods can be used to build interpretable models from data. However, to be really useful, such models must be trusted by their users. From this perspective, the domain expert knowledge can be collected and modeled to help guiding the learning process and to increase the confidence in the resulting models, as well as their relevance. Another issue is to design relevant ontologies to formalize complex knowledge. Interpretable predictive models can help in this matter. In this paper, we propose a generic iterative approach to design ontology-aware and relevant data-driven models. It is based upon an ontology to model the domain knowledge and a learning method to build the interpretable models (decision trees in this paper). Subjective and objective evaluations are both involved in the process. A case study in the domain of Food Industry demonstrates the interest of this approach.