0000000000073682
AUTHOR
M. Le Meste
showing 9 related works from this author
Glass Transition and Food Technology: A Critical Appraisal
2002
ABSTRACT: Most low water content or frozen food products are partly or fully amorphous. This review will discuss the extent to which it is possible to understand and predict their behavior during processing and storage, on the basis of glass transition temperature values (Tg) and phenomena related to glass transition. Two main conclusions are provisionally proposed. Firstly, glass transition cannot be considered as an absolute threshold for molecular mobility. Transport of water and other small molecules takes place even in the glassy state at a significant rate, resulting in effective exchange of water in multi-domains foods or sensitivity to oxidation of encapsulated materials. Texture pr…
Effects of different cellulose derivatives on drug release mechanism studied at a preformulation stage
2003
As a matter of fact, in vitro dissolution is well known to be the method of choice for the pharmaceutical industry to develop effective medicines. However, many experiments must be performed all along a new product life and they represent an overcharge of work for researchers. The purpose of this paper was to assess the relevance of new parameters obtained during preformulation stage by Nuclear Magnetic Resonance (NMR) experiments to better understand drug release mechanism. This study was carried out with three cellulose derivatives currently used as carrier matrices (Microcrystalline cellulose (MCC), Hydroxypropylmethyl cellulose (HPMC) and Ethyl cellulose (EC)). Granules and tablets were…
A contribution to the study of staling of white bread: effect of water and hydrocolloid
1996
Abstract Staling of white bread at ambient temperature was studied using differential scanning calorimetry and dynamic mechanical thermal analysis. During storage, sample hydration varied slightly, from 0 to 0.4% per day, depending on packaging conditions. An increase in rigidity was observed, which was attributed both to starch retrogradation and to changes in the organization of the amorphous part of crumb. The glass transition temperature of crumb was not significantly modified by these structural changes. Hydrocolloids did not affect the overall shape of the viscoelastic behavior of crumb in the temperature range from −40°C to 80°C, and had a limited influence on the kinetics of starch …
Crispness: a critical review on sensory and material science approaches
2002
International audience; Many texture studies have been published on crispness because of the great interest of consumers towards crispy foods. This work reviews the existing literature on the topic, and especially the different approaches, instrumental and sensory, applied to study crispness. These studies result in a wide range of data but, because crispness is not a clearly defined sensory attribute, the conclusions that can be drawn from these studies should be carefully examined. The physical basis for crispness are discussed and the role of structure, hydration and ingredients on crispness and its stability are presented.
Effect of Water on the Mechanical Behaviour of Extruded Flat Bread
1997
Abstract The effect of water on the mechanical properties of extruded breads was studied, at room temperature. As the moisture content was increased from 6 to 9% moisture, the resistance to fracture (compression tests) or rupture (tensile tests) was improved. Above this moisture range, plasticisation by water was the dominant phenomenon. The brittle to ductile transition was observed to occur within a moisture content range from 9 to 13·7% (w/w). The influence of water on the crispness of extruded bread, evaluated with sensory evaluation, is also described.
Reaction Rate Modeling in Cryoconcentrated Solutions: Alkaline Phosphatase Catalyzed DNPP Hydrolysis
2000
The hydrolysis of disodium p-nitrophenyl phosphate catalyzed by alkaline phosphatase was chosen as a model to study the kinetics of changes in frozen food products. The initial reaction rate was determined in concentrated sucrose solutions down to -24 degrees C, and the enzymatic characteristics K(M) and V(max) were calculated. The experimental data were compared to the kinetics predicted by assuming that the reaction was viscosity dependent. Indeed, an analysis of the enzymatic reaction demonstrated that both the diffusion of the substrate and the flexibility of the enzyme segments were controlled by the high viscosity of the media. When the temperature was too low for the viscosity to be …
Dielectric spectroscopy measurements of the sub-Tg relaxations in amorphous ethyl cellulose: A relaxation magnitude study
2005
Amorphous ethyl cellulose exhibits three secondary relaxations at temperatures below its glass transition. The fitted parameters that describe these processes and the comparison with other polysaccharides allow to ascribe the relaxations to lateral groups on one hand and to local main chain motion on the other hand. Their contributions to the dielectric constant overlap and induce a broad dielectric losses peak. The amplitude of one of these relaxations is found to decrease regularly with time. It is believed it comes from a gradual change of the polar groups chemical environment that constrains their motion.
Solubility and diffusion of nitrogen in maltodextrin/protein tablets.
2002
The gas transport properties of compacted tablets consisting of an amorphous mixture of maltodextrin and sodium caseinate were studied by dissolving nitrogen gas in the tablets and then determining the gas release over time as a function of temperature and water activity. Gas was dissolved in the tablet matrix by heating the tablets under pressure, generally to temperatures above the glass transition temperature of the matrix, holding them at these conditions for a specified time and then rapidly cooling them while maintaining the external pressure. The solubility of nitrogen was found to be largely determined by the free volume of the matrix, which in turn can be influenced to some degree …
Contribution of Protein Flexibility to the Foaming Properties of Casein
1990
The effect of biopolymer flexibility on the foaming properties of casein was investigated. Flexibility was altered by: (1) chemical modification (covalent binding of a monosaccharide on the lysyl residues) or (2) pH change. Electron Spin Resonance was used to measure the reorientational frequency of casein residues labeled with nitroxide radicals. High levels of glycosylation induced increased protein flexibility and improved the foaming capacity. Good agreement was observed between higher values of flexibility and improved surface properties near the isoelectric point.