Bernard Cuq

Edible films and coatings as active layers

Edible films and coatings are traditionally used to improve food appearance and conservation. The most common examples are wax coatings for fruit (used in China since the 12th century), chocolate coatings for confectionery, lipid films to protect meat products, and soy milk-based lipoprotein films to improve the appearance and preservation of certain foods in Asia.

Thermal properties of fish myofibrillar protein-based films as affected by moisture content

Abstract Myofibrilar protein-based films were developed from a film-forming solution based on fish mince. The thermal properties of these films were characterized by dynamical mechanical thermal analysis and by differential scanning calorimetry as a function of their water content. During a temperature increase, the films produced sudden changes in mechanical property and specific heat, which are classicaly associated with the glass-rubber transition for amorphous materials. The glass transition was about 20°C broad. Increasing the film water content involved a non-linear decrease in glass transition temperature. The thermodynamic theory of the glass transition (i.e. the Couchman-Karasz equation) was inadequate to describe fully the plasticizing effect of water on the films.

Relative humidity and temperature effects on mechanical and water vapor barrier properties of myofibrillar protein-based films

Abstract Fish mince-based films were studied as a function of equilibrium relative humidity and temperature conditions. The sigmoid-shape adsorption isotherm curves were typical of high protein content material and were adequately described, irrespective of temperature, by the Guggenheim-Anderson-de Boer equation. A plasticizing effect of water related to rapid changes in the functional properties was mainly noted at the highest aw and explained by the disruptive water-polymer hydrogen bonding theory. Relatively sharp decreases in force at break, elastic modulus and water vapor barrier properties, and increases in deformation at break were observed at temperature-dependent relative humidities; this relative humidity was reduced by increasing the temperature. The temperature dependence of the hydration effect on functional properties could be explained by the glass transition theory.

Thermoplastic properties of fish myofibrillar proteins: application to biopackaging fabrication

Abstract Thermoplastic properties of fish myofibrillar proteins were studied by dynamic mechanical thermal analysis. Important changes in dynamic mechanical properties, observed when the temperature was increased, were associated with the glass transition of fish myofibrillar proteins. The glass—rubber transition was observed between 215 and 250°C for the dry material. Addition of water or hydrophilic plasticizers (sucrose and sorbitol) induced large decreases in the glass transition temperature. The depressive effect of water content on the glass transition temperature is described with non-linear relationships. The thermodynamic theory of glass transition (i.e. the Couchman—Karasz equation) was adequate to describe partially the plasticizing effect of water on the myofibrillar proteins. Glassy or foamed biopackagings were obtained by a thermomoulding technique when the process temperature was higher than the glass transition temperature at a given moisture content.

Mechanisms of Heat-Mediated Aggregation of Wheat Gluten Protein upon Pasta Processing

During pasta processing, structural changes of protein occur, due to changes in water content, mechanical energy input, and high temperature treatments. The present paper investigates the impact of successive and intense thermal treatments (high temperature drying, cooking, and overcooking) on aggregation of gluten protein in pasta. Protein aggregation was evaluated by the measurement of sensitivity of disulfide bonds toward reduction with dithioerythritol (DTE), at different reactions times. In addition to the loss in protein extractability in sodium dodecyl sulfate buffer, heat treatments induced a drastic change in disulfide bonds sensitivity toward DTE reduction and in size-exclusion high-performance liquid chromatography profiles of fully reduced protein. The protein solubility loss was assumed to derive from the increasing connectivity of protein upon heat treatments. The increasing degree of protein upon aggregation would be due to the formation of additional interchain disulfide bonds.

X-ray Photoelectron Spectroscopy for Wheat Powders: Measurement of Surface Chemical Composition

The functional properties of wheat powders depend largely on the surface characteristics of their particles. X-ray photoelectron spectroscopy (XPS) has been considered to investigate the surface composition of wheat powders. The objective of the present study is to evaluate the ability of XPS to discriminate wheat components and to calculate the surface composition of wheat powders. First, XPS surveys for the main wheat isolated components (starch, proteins, arabinoxylans, and lipids) were determined. XPS results demonstrate that it is able to distinguish wheat proteins, polysaccharides, and lipids, but it is not able to distinguish starch and arabinoxylan because of their similarity in chemical structure. The XPS analyses of simple reconstituted wheat flours based on two components (starch and protein) or three components (by adding arabinoxylan) demonstrated the ability of XPS to measure the surface composition of the wheat flours. The surface composition of native wheat flour demonstrated an overrepresentation of protein (54%) and lipids (44%) and an underrepresentation of starch (2%) compared to the bulk composition. Results are discussed with regard to difficulties in discriminating arabinoxylans and starch components.

Advances in food powder agglomeration engineering.

Food powders are used in everyday life in many ways and offer technological solutions to the problem of food production. The natural origin of food powders, diversity in their chemical composition, variability of the raw materials, heterogeneity of the native structures, and physicochemical reactivity under hydrothermal stresses contribute to the complexity in their behavior. Food powder agglomeration has recently been considered according to a multiscale approach, which is followed in the chapter layout: (i) at the particle scale, by a presentation of particle properties and surface reactivity in connection with the agglomeration mechanisms, (ii) at the mechanisms scale, by describing the structuration dynamics of agglomerates, (iii) at the process scale, by a presentation of agglomeration technologies and sensors and by studying the stress transmission mode in the powder bed, and finally (iv) by an integration of the acquired knowledge, thanks to a dimensional analysis carried out at each scale.

Etude des parametres de controle et de commande du procede de deshydratation–impregnation par immersion, sur systeme probatoire automatise: application au traitement des pommes “Golden”

Abstract The work presented here is a study aiming at the control and checking of dewatering and impregnation soaking process (DISP). The studies are carried out using an automatic experimental system. Apples of the “Golden” variety are used exclusively. Two kinds of agitation system are studied; mechanical agitation using a vertical screw without an end, and hydraulic agitation. There is hardly any difference between the two kinds of agitation; parameter variations are almost the same. These results are compared with those obtained in agitated thermostated water-bath system and they show that mass transfers are better on the experimental system than with the water-bath system. Temperature influences were studied for the agitated thermostated water-bath system only. They show that the increase of temperature favours water loss and sugar intake. We have shown that during experiments with old syrup, only the conductivity of syrup is higher but kinetics of water loss, solute intake and weight reduction are not significantly affected.

Description of Chemical Changes Implied During Bread Dough Mixing by FT-ATR Mid-Infrared Spectroscopy

ABSTRACT The aim of the present study was to investigate the ability of mid-infrared (MIR) spectroscopy to identify physicochemical changes in the French bread dough mixing process. An ATR FT-MIR spectrometer at 4000–800 cm–1 was used. The MIR spectra collections recorded during mixing were analyzed after standard normal variate using principal component analysis (PCA) and after second-derivative treatment. The results were interpreted in terms of chemical changes involved in dough development and more particularly in terms of secondary structural protein changes (amide III). The loading spectrum associated with principal component 1 (PC1) allows three MIR wave number regions of variations (3500–3000, 1700–1200, and 1200–800 cm–1) to be identified. The loading spectrum associated with PC1 describes an increase in the relative protein band intensities and a decrease in relative water and starch band intensities. The variation during bread dough mixing time of the different amide III bands identified after ...

Steam-jet agglomeration of skim milk powders: Influence of process parameters

ABSTRACT Steam-jet agglomeration consists in steam–wetting of the surface of fine primary particles, colliding the sticky particles and consolidating the agglomerates by drying in order to obtain the desired properties. The aim of this work was to evaluate the influence of the steam/powder ratio and drying time on growth mechanisms and skim milk agglomerate properties. We demonstrated a predominant influence of the steam/powder ratio on the growth mechanisms and agglomerate properties due to the contribution of the steam flow rate. Moreover, the drying time was identified as a key process parameter to control the final water content, rehydration and mechanical properties of the agglomerates. Highlights A steam-jet agglomeration pilot plant was developed to study the agglomeration of skim-milk powders. The growth mechanisms and agglomerates properties depended on the steam/powder ratio, through the contribution of the steam flow rate. The drying time was identified as a key process parameter to control the final water content, rehydration and mechanical properties of the agglomerates.