L'oeuf ingrédient alimentaire

La filière de production et de transformation des œufs occupe une place majeure au sein des industries agroalimentaires avec une production mondiale estimée en 2007 à mille milliards d'œufs. Dotés de propriétés fonctionnelles très performantes, les œufs et les ovoproduits sont devenus omniprésents dans les aliments et constituent des atouts précieux pour le développement de produits nouveaux. Fruit de la collaboration de 35 spécialistes internationaux reconnus, scientifiques et industriels, Science et technologie de l'œuf rassemble en deux volumes tous les savoir-faire et les acquis scientifiques mis à la disposition des acteurs du secteur, de l'amont jusqu'à l'aval de la filière. Il constitue une référence unique dans la littérature professionnelle. Le deuxième volume offre un inventaire technologique complet de la transformation des œufs et propose de nombreuses applications innovantes concernant : les procédés de fractionnement des œufs; les techniques d'élaboration et de stabilisation des ovoproduits; la valorisation des sous-produits; les propriétés fonctionnelles, sensorielles et nutritionnelles de l'œuf; le développement de ses dérivés. Véritable synthèse technique et scientifique, cet ouvrage s'appuie sur de nombreux résultats de recherche et références bibliographiques. Il s'adresse à tous les professionnels du secteur avicole et des ovoproduits (aviculteurs, producteurs d'œufs, fournisseurs et distributeurs) ainsi qu'à tous les services R&D et qualité des industries agroalimentaires. Il intéressera également les organismes de surveillance

An improved non-denaturing method for the purification of spiralin, the main membrane lipoprotein of the pathogenic bacteria Spiroplasma melliferum

Spiralin is the most abundant protein of several species of spiroplasmas, helical, motile bacteria pathogenic for arthropods and plants. This amphiphilic protein is anchored to the outer face of the plasma membrane by a lipoylated N-terminal cysteine. Although spiroplasma pathogenicity in mammals is controversial, it was shown that spiralin is highly immunogenic and endowed with immunomodulatory activity. In this paper, we describe a high performance method for the purification of Spiroplasma melliferum spiralin under non-denaturing conditions. The protein was selectively extracted with 3-[(3-cholamidopropyl) dimethylammonio]-1-propyl sulfonate (CHAPS) from the membrane pre-treated with sodium dodecyl-N-sarcosinate (Sarkosyl), and purified to homogeneity by cation-exchange HPLC with an overall yield of ∼60%. Detergent-depleted, water-soluble micelles of spiralin displaying a mean diameter of 170Å, as evidenced by transmission electron microscopy, were obtained by dialysis detergent removal. Circular dichroism spectroscopy and cross immunoprecipitation assay of the purified spiralin strongly suggested that this purification method could retain the structural characteristics of the native spiralin. The strategy developed to purify spiralin (two successive selective extractions of membrane proteins with mild detergents followed by ion-exchange chromatography) should prove useful for the purification of membrane lipoproteins of other bacteria of the class Mollicutes including different pathogens for humans, animals and plants

Chaperone-signal peptide interactions on the Tat protein transport pathway

Succinimide formation in lysozyme by heating (80°C) in the dry state decreases protein stability but do not impact on secondary or tertiary structure. 34th FEBS congres

Modification of lysozyme by dry-heating: small cause, big effect.

Egg white dry-heating is usually achieved in industry to improve gelling and foaming properties. Major modifications of protein structure have been put forward to explain such functionality improvement. But as for lysozyme, one of the egg white proteins, dry-heating results in a great increase of foaming properties, without any significant modifications of structure, as determined thanks to usual analytical methods for secondary and tertiary structure determination. On the other hand, chemical modifications of the protein sequence could be highlighted for about 40% of lysozyme molecules: up to 5 Asp/Asn residues were changed for succinimide residues after dry-heating for 7 days at 80°C. These modifications result in more tensioactive forms, compared to native lysozyme. However, these "succinimide lysozymes" do not explain all the interfacial properties of dry-heated lysozyme. Indeed, the whole dry-heated lysozyme, that contains other modified forms supposed to be isoaspartate residues, do not have exactly the same behaviour. Finally, it can be concluded that lysozyme dry-heating induces several kind of modifications. And some of these modifications are different from structure changes usually mentioned to explain modification of protein properties. Anyway, dry-heated lysozyme is actually a very efficient foaming agent, contrary to the native one

Comportement interfacial du lysosyme apres traitement thermique a sec

Comportement interfacial du lysosyme apres traitement thermique a sec. 4. Rencontres Biologie-Physique du Grand Oues

Air-Water interface: a key place for revealing protein interactions.

International audienceFrom their amphiphilic nature, proteins in solution adsorb spontaneously at hydrophobic interfaces. Proteins are thus able to change their conformation, which modifies their surface properties. In the confined space near the interface, these modifications favor the formation of many interactions of weak energy (hydrophobic interactions, hydrogen bonds, Van der Waals interactions), and thus the creation, in the interface plane, of a network of intermolecular interactions. Adsorbed proteins can thus, in favorable conditions, constitute at the interface a continuous film with visco-elastic properties. These mechanical properties contribute to the stabilization of the interface created in multiphasic systems such as foams. Our work focuses on the behavior at the air-water interface and, if needed the foam properties, of some model globular proteins: ovalbumin, lysozyme, ovotransferrin, β-lactoglobulin… The aim of our work is to understand, using these models, how protein properties (structure, biochemistry, physico-chemistry), potentially adjusted by the physico-chemical environment, chemical changes or thermo-mechanical treatments, take part in the interfacial behavior, film characteristics and macroscopic proprieties of foams (overrun, stability, texture). Besides, in systems where several proteins with different properties (size, hydrophobicity, charge, conformation flexibility,…) coexist, we look to understand how the interactions between proteins enhance behaviors that cannot be considered as the sum of the single behaviors. The issue over time is to control technological parameters to improve texture properties in relation to foaming capacity

Dry heating of egg white proteins: how a multiscale approach may help to predict foaming properties from 2D interface measurements

Dry heating is performed in egg product industries to pasteurise egg white powder. This treatment (55 to 80°Cduring a few days) is also used to improve egg white powder functional properties among other foamingproperties. Several studies have shown this foaming properties‟ improvement with dry heating length (Kato etal, 1989; Baron et al, 2003; Van der Plancken et al, 2007; Talansier et al, 2009) that Kato et al (1989) attributedto protein surface hydrophobicity increase. However, during these treatments, soluble and insoluble covalentaggregates were also generated (Kato, 1989; Van der Plancken et al, 2007; Talansier et al, 2009) that may beinvolved in foaming properties improveme nt. Conclusions from such a complex protein solution as egg whiteare difficult to draw; this is the reason why we choose ovalbumin, the major egg white protein (54% of totalprotein amount) and lysozyme (one of the most famous model protein) to identify the molecular speciesgenerated by dry heating that are responsible for foaming properties‟ improvement. Ovalbumin and lysozymefoaming properties are improved after dry heating (Kato, 1990a) and the protein undergoes some mildconformational changes close to the molten globule state as well as aggregation driven by hydrophobicinteractions and disulfide bonding (Kato, 1990b; Matsudomi, 2001). The present study has been performed toidentify the molecular species generated by dry heating responsible for foam ing properties improvement. Mostof the data of the literature were confirmed as we found that ovalbumin and lysozyme aggregated and thatdeamidation occurred. We also identified less negatively charged ovalbumin that we attributed todephosphorylation. We performed surface pressure and ellipsometric angle measurement on dry heatedovalbumin but also on dephosphorylated, desamidated and aggregated forms. Dry heated ovalbumin andlysozyme show faster adsorption kinetics to air water interface than non-heated one. However the equilibriumsurface pressure and surface concentration are quite close for ovalbumin whereas no equilibrium were reachedfor lysozyme. Shear elastic constant measurement showed higher values for dry heated ovalbumin during thefirst hour but no significant difference after 8 hours. Measurements of dilatational and shear modulus were alsoperformed to complete the data. Foaming properties of the different molecular species were measured whenpossible. This multidimensional approach helped in the understanding of the characteristic of the interfacial filmthat explain foaming properties. It seems that more than the values of surface pressure, ellipsometric angle orcomplex modulus at the equilibrium, it is the evolution of these values in the first few stage that is important topredict foaming propertie

How the physicochemical and structural properties of globular proteins affect their behavior at the air-solution interface and their foaming properties

We have been studying the behavior of several globular food proteins at the air-solution interface and their capacity to stabilize aqueous foams. Our aim is to understand the relation of foaming ability to the properties of the adsorbed protein layer, and to understand the relation of the properties of the adsorbed protein layer to the structural and physicochemical characteristics of the adsorbed protein(s). We used a combination of techniques providing insight in the adsorption kinetics (ellipsometry, surface tension), in the interfacial shear rheology and in the molecular conformational rearrangements of adsorbed proteins (polarization-modulation infrared reflection-absorption spectroscopy, PM-IRRAS). We compared proteins with distinctive molecular features, native and chemically or physically modified forms of one protein, and studied the interfacial behavior of proteins in binary solutions. We found that depending on the physicochemical adsorption conditions, different proteins form qualitatively different interfacial layer, as regards monolayer or multilayer adsorption, or the interfacial shear rheology. Strikingly, very minor structural modifications prior to adsorption to the air-solution interface could lead to dramatic changes in the interfacial behavior, in parallel to dramatic changes in the foaming ability. We also showed that in the case of binary solutions of oppositely charged proteins, a clear co-adsorption occurs, leading to very high surface concentrations and to deeply modified interfacial film properties, which cannot be extrapolated from the addition of individual behaviors. In addition, preliminary results about the osmotic pressure of bulk, very highly concentrated protein solutions suggest that in interfacial studies, due to the protein crowding close to the interface, intermolecular interactions could be of prominent importance in the understanding of interfacial properties

Vers un contrôle des propriétés macroscopiques des milieux dispersés par les propriétés associatives des protéines alimentaires

National audienceMany food proteins as egg white or milk protein show tensioactive properties. This means that one region of the protein has affinity for polar environment and another region of the protein prefers an apolar environment. For that reason, these proteins tend to adsorb to amphiphilic-hydrophobic interfaces such as air-water interface of bubble surface in case of foams or oil-water interface of droplets surfaces in case of emulsions. In both cases, food proteins act as stabilizers of the dispersed medium. In addition, and in contrast with small-molecular weight surfactants, proteins can also self-associate and form an interfacial film with viscoelastic properties, which also contributes to stabilization.However, their tensioactive properties confer to food proteins striking associative properties that this presentation will illustrate following three ideas:The mixture of two proteins as components of a dispersed medium can lead to enhanced bulk properties compared to the case where each protein is alone, even if one protein is in very small amount in the mixture. This property offers the possibility to modulate bulk properties of a mixture using one protein as an additive. The case of foaming properties of ovalbumine-lysozyme will illustrate this idea. We have shown (1,2) that the interaction between proteins preferentially takes place at the air-water interface and that the interfacial adsorbed film is stratified, the most tensioactive protein being adsorbed first.The association of two proteins can lead to the formation of monodisperse microspheres, the ratio of each protein in the microsphere depending on the charge ratio. This property is illustrated by the case of the mixture alpha-lactalbumine/lysozyme (3). We have shown that the first steps of these bulk associative properties are revealed by the interfacial properties of these proteins.The last part of this presentation shows how very slight modifications of a protein, hardly detectable with standard bulk caracterisation tools, can lead to drastic changes in foaming and interfacial properties. The case of dry-heated lysozyme will be exposed, for which we haveshown (4) that a modification of one unique aminoacid greatly affects the interfacial properties of the protein and consequently greatly enhance the bulk properties of the foam. It evidences that small changes on a protein can act as a swich relative to the bulk properties of the dispersed media stabilized with this protei