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This review is respectfully dedicated to the memory of Michel Ollivon, Research Director at CNRS (Châtenay-Malabry, France), outstanding physico-chemist specialist of lipid organization, recipient of the Hilditch Memorial Lecture award, who was the initiator of the network RMT LISTRAL. We are also sadly paying tribute to Jean-Luc Vendeuvre, Food Engineer at the French Pork and Pig Institute (IFIP, Maisons-Alfort, France), outstanding expert in meat products who participated actively in RMT LISTRAL and provided unpublished data for figures in the present review, who passed away during review submission. RMT LISTRAL: Mixed Technological Network combining academic and industrial partners, devoted to the enhancement and divulgation of knowledge regarding structured dietary lipids.; International audience; On a nutritional standpoint, lipids are now being studied beyond their energy content and fatty acid (FA) profiles. Dietary FA are building blocks of a huge diversity of more complex molecules such as triacylglycerols (TAG) and phospholipids (PL), themselves organised in supramolecular structures presenting different thermal behaviours. They are generally embedded in complex food matrixes. Recent reports have revealed that molecular and supramolecular structures of lipids and their liquid or solid state at the body temperature influence both the digestibility and metabolism of dietary FA. The aim of the present review is to highlight recent knowledge on the impact on FA digestion, absorption and metabolism of: (i) the intramolecular structure of TAG; (ii) the nature of the lipid molecules carrying FA; (iii) the supramolecular organization and physical state of lipids in native and formulated food products and (iv) the food matrix. Further work should be accomplished now to obtain a more reliable body of evidence and integrate these data in future dietary recommendations. Additionally, innovative lipid formulations in which the health beneficial effects of either native or recomposed structures of lipids will be taken into account can be foreseen.

Revue réalisée en hommage à Michel Ollivon (Directeur de Recherche au CNRS, UMR8612, Châtenay-Malabry), décédé en juin 2007, qui a été à l’origine de la création du RMT Listral. Ce Réseau Mixte Technologique avec pour thématique les Lipides Structurés Alimentaires est coordonné par l’ACTIA et animé par Actilait. Les autres partenaires du réseau sont : F Sobolewski & JP Bodin (Enilia-Ensmic), K Duhem & JP Guyonnet (Cniel), JP Bergé & JP Gouygou (Ifremer Nantes), G Nassy (Ifip), Lebois & D Majou (Actia), P Gaborit & R Richoux (Actilait).; National audience; From the nutrition point of view, lipids are primarily considered as energy suppliers, their dietary intake having to be limited. In fact, lipids are sources of various fatty acids, and dietary recommendations include the required daily intakes in different fatty acids (fatty acid profile). Beyond these quantitative aspects, fatty acids are part of larger molecules, mainly triacylglycerols (TAG), that are organized in supramolecular structures as for example fat crystals and lipid droplets. Recent advances in nutrition research have demonstrated that these structures, and lipid organization in food matrices, influence digestibility and metabolism of fatty acids. Therefore, the members of the technological network Listral propose a synthesis of the knowledge about the influence of molecular and supramolecular structures of lipids on digestion and metabolic fate of dietary fatty acids originating from for the main food industry sectors. Fatty acids are mainly provided in the diet in the form of TAG, or phospholipids (PL) where they are esterified in external (sn-1, sn-3) or internal (sn-2) position of the glycerol backbone. They can also be found as ethyl esters (EE) in specific formulations. These molecular characteristics of the lipid molecules affect their hydrolysis and their absorption rate but also their metabolism in indifferent organs, as assessed in studies often using inter esterified fat sources. The results depend on the types of fatty acids (saturated or polyunsaturated fatty acids) but also on the model used for the studies: in vitro or in vivo studies ; animal model, human newborn or adult, either healthy or exhibiting some diseases. Among others, it was found that the crystal form and fat melting point as affected by the fatty acid profiles and the lipid molecular structures directly impact fatty acid absorption kinetics through modifications of lipolytic enzyme activities. However, in these studies, the relative effect of the thermal properties of lipids and the proportion of saturated fatty acids chains in sn-2 position were hardly distinguished. Supramolecular structures, namely type and size of the fat droplets and their interfacial composition, of lipids, either in their native forms or obtained after food processes, also affect the digestibility and absorption of lipids. This aspect is reviewed with specific focus on dairy, marine, meat, oil plant and egg products. The impact of other nutritional components present in these food matrices on the absorption of lipids is also discussed.

Multiple stars are found in quite large proportions among young low-mass objects, T Tauri stars, and among Main Sequence stars as weIl. However, the binarity status of young intermediate mass objects, Herbig AejBe stars (HAeBe), is far less known. We have thus conducted a systematic search of HAeBe binaries using two technies: high angular resolution imagery with Adaptive Optics and high resolution visible spectroscopy. These two complementary technies have allowed us to identify more than twenty new multiple stars among HAeBe; the deduced binary frequency is at least 50 %, may be more due to observationnal bias. For the first time, spectral type of companions have been determined for about twenty visual binaries. The implications of our observations for the presence of dust disks around HAeBe and X-ray emission detection in HAeBe are presented. Observational constraints for star formation mechanisms are discussed. An important part of the thesis is devoted to the study of the triple star TY CrA, the only spectroscopic hierarchical system among Herbig AejBe stars. After a complete description of the orbital and stellar parameters, a dynamical modelisation of this particular object is presented. Our theoretical investigations show that the stability of the system is insured by tidal effect inside the central eclipsing binary. The circumstellar environment of TY CrA has also been studied with infrared spectroscopy using the spatial telescope ISO and with Adaptive Optics images in the near infrared., Les étoiles multiples sont nombreuses, tant parmi les objets jeunes de faible masse, les étoiles T Tauri, que parmi les astres de la Séquence Principale (SP). En ce qui concerne les étoiles jeunes de masse intermédiaire, les étoiles Ae/Be de Herbig (HAeBe), le statut de la binarité est peu connu. Nous avons réalisé une recherche systématique de binaires HAeBe en utilisant deux techniques: l'imagerie à haute résolution angulaire avec la méthode de l'Optique Adaptative d'une part, et la spectroscopie visible à haute résolution d'autre part. Ces techniques complémentaires nous ont permis d'identifier plus d'une vingtaine de nouvelles étoiles binaires; la fréquence de binarité déduite est d'au moins 50 %, voir supérieure à cause des biais observationnels discutés dans la thèse. Pour la première fois, les types spectraux des compagnons ont pu être déterminés dans une vingtaine de systèmes visuels. Les implications de nos observations pour la présence de disques de poussières et la détection d'émission X dans les étoiles HAeBe sont présentées. Les contraintes apportées pour les théories de formation des binaires sont discutées. Une partie importante de la thèse est consacrée à une étude approfondie de l'étoile triple TY CrA, l'unique système spectroscopique hiérarchisé parmi les étoiles Ae/Be de Herbig. Après une description complète des paramètres orbitaux et stellaires, la modélisation de la dynamique de cet objet particulier a été réalisée. Nos calculs théoriques montrent que la cohésion du système est assurée par effet de marée à l'oeuvre dans la binaire à éclipse centrale. L'environnement circumstellaire de TY CrA a également été étudié à partir d'observations spectroscopiques infrarouges avec le télescope spatial ISO et à partir d'images en Optique Adaptative dans le proche infrarouge.