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International audience; BACKGROUND. High circulating levels of ceramides (Cer) and sphingomyelins (SM) have been associated with cardiometabolic diseases. The consumption of whole-fat dairy products, which naturally contain such polar lipids (PL), is associated with health benefits, but the impact on sphingolipidome remains unknown. We investigated how milk PL supplementation impacts circulating and intestinal SM and Cer composition in association with improvement of cardiovascular markers.METHODS. In a 4 week-randomized double-blind controlled study, 58 postmenopausal women consumed daily a cream cheese containing 0, 3 or 5 g of milk PL. Postprandial metabolic explorations were performed before and after the supplementation. SM and Cer species were analyzed in serum, intestine-derived chylomicrons and feces. The ileal content of 4 ileostomy patients was also explored after milk PL intake in a crossover double-blind study.RESULTS. Milk PL consumption decreased serum atherogenic C24:1 Cer (Pgroup = 0.033), C16:1 (Pgroup = 0.007) and C18:1 (Pgroup = 0.003) SM species. Changes in serum C16+18 SM species were positively correlated with the reduction of total cholesterol (r = 0.706, P < 0.001), LDL-C (r = 0.666, P < 0.001) and ApoB (r = 0.705, P < 0.001). Milk PL decreased the concentration in chylomicrons of total SM (Pgroup < 0.0001) and of C24:1 Cer (Pgroup = 0.001). Saturated SM and Cer species, which are also the major species found in milk PL-enriched cheeses, increased in ileal efflux and feces. There was a marked increase in total fecal Cer after milk PL supplementation (Pgroup = 0.0002). Milk PL also modulated the abundance of some specific SM and Cer species in ileal efflux and feces, suggesting differential absorption and metabolization processes in the gut.CONCLUSION. These data demonstrate that milk PL supplementation decreases atherogenic SM and Cer species associated with an improvement of cardiovascular risk markers. Our findings bring new insights on sphingolipid metabolism in the gastrointestinal tract, especially Cer as such signaling molecules potentially participating in the beneficial effect of milk PL. ClinicalTrials.gov, NCT02099032, NCT02146339.

Dietary lipids play a major role in infant nutrition, development and health. As an alternative to breast milk, infant formulae (IF) are the manufactured products given to infants. However, many differences exist between breast milk fat globules that are naturally secreted by lactating mothers and the processed lipid droplets formed under pressure during homogenization and found in IF. The lipid composition and structure of the emulsion in IF could be improved to mimick breast milk fat globules. This book chapter i) describes breast milk fat globules covered by their biological membrane (MFGM), including their functions and digestion in the gastrointestinal tract of infants, ii) presents the technological steps involved in IF preparation and the blending of oils with other ingredients leading to the final composition and structure of processed lipid droplets, iii) highlights the health benefits for infants of adding dairy lipids (Fatty acids, TAG, MFGM rich in phospholipids, sphingolipids, cholesterol and glycoproteins) in IF, iv) explains the opportunities to produce food-grade ingredients enriched in bovine MFGM and to prepare processed lipid droplets in IF bio-inspired by breast milk fat globules. The next generation of IF will integrate the advantages provided by dairy lipids to improve the quality of IF and bring nutritional and heath benefits to infants worldwide.

Bovine milk fat is an important dairy component which is consumed by human infants and adults via various dairy products such as milk, milk powder, cream, cheeses, and butter. Apart from the major physiological role of milk fat in delivering human nutrition and providing health benefits, milk fat also plays as a pivotal func-tionality controlling role in many dairy products. The biological membrane sur-rounding milk fat globules has been found to have interesting applications in food formulation innovations, human nutrition, and paediatrics. Therefore, understand-ing the fundamental science and technology of milk fat is of great importance not only from a scientific point of view but also with regard to the economic impact of milk fat, especially in fat-rich products. The intention of this book is to provide readers with recent and outstanding literature in important areas of dairy fat contain-ing products and functionality. This book represents a valuable source of informa-tion for students, academics, and industry personnel who work in the fields of dairy lipids and dairy fat products.In this book, 24 chapters have been organised into three main themes: (1) dairy fat chemistry and nutrition, (2) dairy fat physics and materials science, and (3) dairy fat processes and products. In the first theme, fascinating insights into milk fat glob-ule membrane such as structure, lipidomic characterisation, and applications are presented. Physiochemical characterisation, lipase action, adulteration, and digest-ibility of milk lipids are also covered. The second theme provides excellent funda-mentals in physical properties of milk fat such as crystallisation, rheology, and microstructure aspects. It also highlights relatively new research areas driven by material science approach in dairy fats, where innovative dairy products and the new generation of dairy ingredients can be tailor-made. Cutting-edge topics on tri-bology of dairy fat products, oil structuring in dairy fat products, manipulation of differentiated-sized milk fat globules, and production of human milk fat substitutes from dairy fats are featured in dedicated chapters. The third theme presents compre-hensive reviews on the relationship among processes—structure—functionality in dairy fat products towards new developments in manufacturing processes and health-promoting dairy products. The last theme also focuses on the importance of vimilk fat as a key quality controlling factor in the manufacturing of butter, ghee, dairy cream, dairy powder, cheeses, and aerated products.The expert contributions of 43 authors from 10 countries are greatly acknowl-edged with gratitude. Special acknowledgements are also extended to Springer for their support during the course of this book project.

Introduction Human milk is a complex biological fluid recognized as the gold standard in neonatal nutrition, especially for preterm infants since it supports growth and brain development. Donor human milk, pasteurized for safety reasons, is the first option to feed preterm infants when mothers’ own milk is not available. Objective The aim of the present study was to determine the impact of breastmilk pasteurization on preterm gastrointestinal digestion and to evaluate its effect on lipid absorption. Methodology Kinetics of digestion and structural desintegration of pasteurized human milk (PHM) and raw human milk (RHM) were evaluated using a static in vitro digestion model that we adapted to simulate preterm digestion ability. Caco-2 /TC7 cells, an intestinal absorption model, were subsequently incubated with diluted PHM vs RHM-digestion media. Main findings During in vitro digestion, proteolysis was evaluated by SDS-PAGE followed by densitometry. Lactoferrin proteolysis was significantly (p

The rheological properties and microstructure of dairy gels involve the connectivity between milk fat globules (MFG) and casein micelles that is affected by technological processes such as milk homogenization and heat treatment. The underlying mechanisms require further quantification of the interactions at the nanoscale level to be fully understood and controlled. In this study, we examined the adhesion of homogenized MFG to milk proteins and evaluated the role of ultra-high temperature (UHT) heat treatment and pH. The combination of physico-chemical analysis, rheology and microscopy observations at different scale levels associated to atomic force microscopy (AFM) force spectroscopy were used. AFM experiments performed at the particle scale level showed that adhesion of individual homogenized MFG to milk proteins (1) is increased upon acidification at pH 4.5: 1.4 fold for unheated samples and 3.5 fold for UHT samples, and (2) is enhanced by about 1.7 fold at pH 4.5 after UHT heat treatment of milk, from 176 pN to 296 pN, thanks to highly-reactive heat-denatured whey proteins located at the surface of MFG and caseins. The increased inter-particle adhesion forces accounted for more connected structures and stiffer UHT milk acid gels, compared to unheated-milk gels. Using a multiscale approach, this study showed that heat treatment of milk markedly affected the interactions occurring at the particle’s surface level with consequences on the bulk structural and rheological properties of acid gels. Such findings will be useful for manufacturers to modulate the texture of fermented dairy products through the tailoring of heat-induced complexation of proteins and the connectivity of homogenized MFG with the protein network. This work will also contribute in a better understanding of the impact of process-induced changes on the digestibility and metabolic fate of proteins and lipids.

International audience; In their native state, milk lipids are present in the form of dispersed droplets called Milk Fat Globules (MFG, diameter 0.1-20 μm, average = 4 μm in bovine milk) [1,2]. The native MFG is constituted by a triglyceride core covered with an external trilayered membrane inherited from its secretory past. This membrane is mainly based on polar lipids (glycerophospholipids, sphingolipids and glycosphingolipids), proteins (25 % of total membrane with high proportion of glycoproteins and enzymes), neutral lipids and minor components. The major biological function of the MFG is to deliver energy to the mammal newborn, for that, the MFG has to be hydrolyzed in the gastro-intestinal tract by lipases, in successive steps. The lipases should interact with the MFG membrane and diffuse into the supramolecular object. The aim of this work was to determine the mechanisms involved in the enzymatic hydrolysis along the digestive process. We used millifluidic cells designed to trap MFG or model droplets and injected successively each lipase (gastric, pancreatic related 2, pancreatic triglyceride lipase) involved in the digestion process and thus mimicking different physiological stages (preterm infant, fullterm infant and adult). Thanks to the deep UV-microscope present at DISCO beamline, the autofluorescence of tryptophan (and tyrosine) of lipase aminoacids allowed protein observation without external labeling. The gastric and intestinal neonatal disintegration of milk fat globules (human or bovine) or other model systems (bovine anhydrous milk fat droplets stabilized by bovine milk membrane extracts or soy lecithin) was approached through transmission images recording. The analysis of the number of globules and their state of aggregation/coalescence during digestion (approached via diameter, size, mode and specific surface evolution against time) gave indication on the kinetics and mechanisms of lipolysis. Fluorescence (327-335 nm) image indicated lipase distribution. Gastric phase was mainly marked by the heterogeneous adsorption of the gastric lipase in the MFG membrane. Afterwards, heterogeneous adsorption of pancreatic triglyceride lipase could also be observed followed by the disappearance of the MFG core. The progression of lipases fronts was monitored and the kinetics of lipolysis characterized allowing the differentiation of substrate and of in vitro digestion models (full term infant, versus preterm infant versus adult). The microfluidics set up was a very interesting tool to follow sequentially the action of lipases, to save volume of purified lipase and to image simultaneously several positions. The high sensitivity of the DISCO beamline allowing the detection of digestive lipases auto-fluorescence, is a unique tool to unravel their mechanisms of adsorption onto complex substrate using free-label imaging and has generated useful data for infant formula optimization

Objectives: Nutritional strategies can play a major role in the management of cholesterolemia, notably in postmenopausal women at risk of CVD. Interest has recently grown on the potential health benefitsof milk polar lipids (MPL).We showed that isolipidic enrichment of the diet with MPL improved several lipid CV risk factors but underlying mechanisms remained unclear. We hypothesized that MPL reduceintestinal cholesterol absorption in humans.Methods:We performed a double-blind randomized controlled trial in 58 postmenopausal women with fasting HDL-cholesterol < 1.6 mM.They were subjected to a 4-week dietary intervention with daily consumption of a cream-cheese containing 12 g of milk fat including either 0 g (control, n = 19), 3 g (n = 19) or 5 g (n = 20) of MPL. Before and after each intervention, blood lipids were measured in the whole cohortwhereas fecal lipids and coprostanol were analyzed in a subgroup (n = 7–9 per group). A proof-of-concept mechanistic crossover study was also carried out in 4 ileostomized subjects who performed 8hpostprandial tests after consuming 0g-, 3g- or 5g-MPL enriched cheese labelled with 2H-cholesterol tracer. Plasma, chylomicrons and ilealefflux were analyzed.Results: Milk fat enriched with 3 to 5 g MPL induced doseresponse reductions in serum total cholesterol (up to −6.8% in 5 g group, p < 0.05), LDL-cholesterol (−8.7%, p < 0.05) and HDL/total-cholesterol ratio (p < 0.001), compared to the control that had no effect. Fecal excretion of coprostanol increased after MPL supplementation (p < 0.05, 3g- and 5g-MPL vs control), and the fecal coprostanol/cholesterol ratio was inversely correlated with serum total- and LDL-cholesterol after intervention (r = −0.5, p < 0.05). In ileostomized subjects, postprandial accumulation of 2Hcholesterol in plasma and chylomicrons was reduced after 3 to 5 g MPL consumption (p < 0.05, vs control). Both cholesterol and milk sphingomyelin increased in ileal efflux after MPL enriched cheeses (p < 0.05).Conclusions: Present results suggest that milk polar lipids decrease cholesterol absorption in humans through interactions with sphingomyelin and by increasing conversion of cholesterol to coprostanol.Funding Sources: ANR (French National Research Agency, VALOBAB project, ANR-11-ALID-007–01), PHRC-I (French Clinical Research Program, 14–007), CNIEL (French Dairy Interbranch Organization).

Deciphering the interfacial properties of the milk fat globules and the impact of processing using a multi-scale biophysical approach. Première réunion plénière du GDR SLAMM (Solliciter LA Matière Molle)

Increasing knowledge about the composition and biophysical properties of milk lipids is essential to better understand, modulate and control their properties in food products, to developinnovative functional foods but also to tailor specific lipid structures able to provide nutritional and health benefits. Milk lipids are an important source of energy and bioactive molecules for the optimal growth and development of breast-fed newborns. They are also involved in the functional properties and sensory quality of many dairy products that are consumed by adults[1]. Milk is a natural O/W emulsion in whichfat globules are highly complex and unique entities as regard to the wide diversity of lipid molecules (98% triacylglycerols withmore than 400 fatty acids characterized byvarious chain length and saturation; polar lipidscontaining 30% sphingomyelin, cholesterol) and the multiscale organization of lipids (mean diameter of fat globules 4 µm; crystals of TAG; trilayer of polar lipids in the biological membrane).The structure of milk lipids, both TAG and polar lipids, is affected by temperature and thermal kinetics that induce phase transitions. Dairy processingalso have a major impact on the structure of milk lipids, with consequences on their reactivity in complex dairy products, mainly interactions with milk proteins[1].Thelecturewill provide an overview of the specificities of milk fat globules in terms of composition, structure and functions.Moreover, the recent advances about the structure of the milk fat globule membrane including the dynamics of the lipid domainsrich in sphingomyelin and cholesterol that are responsible for topographical and mechanical heterogeneities will be presented [2,3,4]. The development of processed emulsion droplets bio-inspired by milk fat globules to improve the structure of lipids in infant formulas and narrow the gap with human milk will also be described [5].These recent and new findingswill undoubtadelyopen perspectives in dairy technology and human nutrition(infants and adults).

The biological membrane surrounding fat globules in milk (the MFGM) is poorly known despite its importance in the functional properties of many dairy products,in the mechanisms of milk lipids digestion occurring in the gastrointestinal tract and the increased scientific evidence of its health benefits.Studies recently revealed the formation of lipid domains inthe MFGM that havebeen interpreted as the lateral segregation of high phase transition temperature (Tm) lipids, mainly milk sphingomyelin (MSM; Tm 34°C), and cholesterol[1]. The properties ofthese MSM-rich domains and their functional rolein the MFGM arecurrently unknown and needs further investigation. The aim of this study was to investigate the biophysical properties of hydrated MSM bilayers in absence or presence of increased amount of cholesterol. The experiments have been performed using synchrotron radiation X-ray diffraction and differential scanning calorimetry[2].Also, the interactions between MSM and cholesterol have been investigated in monolayers composed of various MSM/cholesterol molar ratios by the recording of Langmuir isotherms of compression both for temperatures below and above Tm of MSM [3,4]. The role of cholesterol in the topography and mechanical properties of hydrated bilayers composed of MFGM polar lipids has been characterised using atomic force microscopy [5]. This study allowed the characterisation of the gel and liquid crystalline phase of MSM bilayers as well as their structural changes as a function of temperature. The addition of more than 40% mol cholesterol induces the formation of the liquid ordered phaseand dedrease the rigidity oft he membrane as compared to the MSM gel phase. These results improved knowledge about MSM properties and its interactions with cholesterol that areinvolved in the formation of complexes in the MFGM and potentially in the gastrointestinal tractduring digestion of milk fat globules.

Introduction P. freudenreichii is used both as Swiss-type cheese starters and as probiotics. For these purposes, it should be converted into a powdered form to be stabilized, without significant loss of viability. Freeze-drying and spray drying can be implemented in order to obtain dry starters or probiotics. Compared to freeze-drying, spray-drying requires less energy for water removal; however, the use of spray-drying involves exposure to air at high temperatures during the process. It is thus a stressful process, with simultaneous thermal, oxidative and osmotic stresses. To resist to these latter, bacteria should adapt their physiology. Culture media constitute a means to adapt bacteria in the aim to increase their survival during spray drying. Aim In this study, we explored the influence of the growth medium composition on 1) osmoprotectants accumulation and 2) bacteria survival during spray drying. Methods In rich YEL medium, the salt concentration chosen was the highest still allowing growth of P. freudenreichii CIRM BIA 129. For all experiments, cells were collected at the beginning of the stationary phase. Accumulated osmoportectants were identified and quantified by C and H NMR. The different cultures were then submitted to oxidative, heat, and spray drying challenges. Results During growth, P. freudenreichii CIRM-BIA 129 accumulated trehalose, glutamate and glycine betaine. In hyper-osmotic conditions, the accumulation of these osmoprotectants increased.Lactose, which is naturally present in sweet whey, or lactose added to YEL growth medium, triggered acid adaptation, but also increased intracellular trehalose accumulation. The glycine betaine/trehalose ratio accumulated in intracellular content was determined by the culture medium carbon/azote ratio.With an optimized intracellular glycine betaine/trehalose ratio, P. freudenreichii better survived heat and oxidative lethal challenges, as well as spray drying. Conclusion Designing the culture medium composition allows driving bacterial adaptation and leads to better survival after spray drying. This, in turn, should lead to high yield and high-quality production of starters and probiotics.

Interactions between biological membranes and proteins are crucial in biological functions such as cell signaling, trafficking or in the control of membranes’ physical stability or functional properties. Over the last decades, the nanoscale resolution of Atomic Force Microscopy (AFM) has allowed direct observation of such interactions in near-physiological conditions[1]. Among biological membranes, the milk fat globule membrane (MFGM) is of special interest as the interface with the surrounding bulk of milk proteins during dairy processes or with enzymes and tissues of the gastro-intestinal tract during digestion. The MFGM is composed of polar lipids showing either zwitterionic, e.g. milk sphingomyelin (MSM) and phosphatidylcholine (PC), or anionic head groups, e.g. phosphatidylserine (PS) and phosphatidylinositol (PI). It exhibits lateral heterogeneity with microdomains of MSM in gel-phase or in liquid-ordered (Lo) phase in the presence of cholesterol, surrounded by the fluid matrix of glycerophospholipids, ie DOPC, in the liquid-disordered (Ld) phase[2,3]. In the present study, our goal was to determine how the phase and charge states of MFGM polar lipids drive interaction with the casein micelles, as the major milk protein 100-nm assembly, negatively charged at pH 6.7. For that, supported-hydrated lipid bilayers with various lipid compositions were prepared, including MFGM polar lipid extract, MSM, MSM/cholesterol, MSM/DOPC, DOPC/PS/PI. AFM topography imaging was performed before and after injection of casein micelles in the environment. Zeta-potential and Langmuir isotherms of the different polar lipids gave additional information necessary to interpret AFM observations. No interaction was observed between the casein micelles and the organized phases of MSM in gel-phase or MSM/cholesterol in Lo phase. But the casein micelles did adsorb onto the Ld phase of DOPC (figure 1), probably as a result of its larger inter-molecular distance. However, the presence of anionic polar lipids, PS and PI, in the Ld phase prevented such interaction by inducing electrostatic repulsion of the casein micelles. Thus, interaction of casein micelles with the MFGM is controlled by the phase state and the ionisation of its constitutive polar lipids. These results open perspectives for the design of emulsions and liposomes with variable capacity for protein adsorption, using milk polar lipids as food-grade ingredients.

Ceramides are minor structural components of membranes involved in biological functions. In the milk fat globule membrane (MFGM), ceramides are susceptible to affect the lateral packing of polar lipids, especially the milk sphingomyelin (MSM). To investigate this, palmitoylceramide (PCer) was added to MSM/DOPC (dioleoylphosphatidylcholine) in order to form hydrated lipid bilayers. Differential scanning calorimetry evidenced interactions of PCer with the MSM in the solid-ordered phase to form MSM/PCer structures with a higher thermostability than MSM. Atomic force microscopy revealed that PCer modified lipid packing in both the liquid-disordered DOPC phase where it increased thickness and mechanical stability, and the solid-ordered MSM phase where it recruited MSM molecules yet initially in the liquid phase at 26 °C and then increased the area of the MSM/PCer domains. The effect of PCer on the mechanical properties of the MSM-rich domains remains to be elucidated. These results bring new insights on the role of ceramides in the control of biophysical and biological properties of the MFGM. They also open perspectives for the design of emulsions and liposomes, using milk polar lipids as food-grade ingredients.

Le fromage est un produit connu et élaboré par l’homme depuis des millénaires. Il est lié à la domestication des espèces laitières et à la connaissance empirique de la richesse nutritionnelle du lait, la transformation du lait en fromage répondant au besoin de conservation de cet aliment.Le Fromage réunit l’essentiel des connaissances aujourd’hui disponibles sur ce produit, qu’il aborde sous l’angle scientifico-technique. Ainsi, les fondamentaux et les lois de la biochimie et de la physico-chimie les mieux établies actuellement concernant la transformation du lait en fromage sont-ils présentés et analysés. La 4e édition de ce traité intègre également la réglementation spécifique à ce produit laitier, les réoccupations grandissantes des consommateurs en matière d’alimentation et les nouveaux modes de consommation, les interrogations des autorités de santé publique relatives aux relations possibles entre les régimes alimentaires et la santé, les évolutions à venir.Les chapitres s’articulent ainsi autour de six grandes parties :■ Histoire■ Aspects réglementaires■ Science et technologie■ Consommation■ Qualité■ Perspectives

The interactions between milk polar lipid membrane bilayers and the casein micelles depend on the phase state and charge. 16. Euro Fed Lipid Congress Fats, Oils and Lipids: Science, Technology and Nutrition in a Changing World

The crystallization properties of milk fat can be affected by many parameters such as the cooling rates and thermal history, the shear, the presence of minor lipid components, the dispersion state (anhydrous versus emulsified), and the changes in the fatty acids (FAs) and triacylglycerols (TAG) composition. Milk TAG crystals are involved in the rheological and sensorial properties of products. Besides solid fat content, the functionality of a fat is also affected by the crystal structure formed by TAGs. TAGs represent generally 97‐98% of milk fat. The balance is composed mainly by minor lipids such as free fatty acids (FFAs), monoacylglycerols (MAGs), diacylglycerols (DAGs), and phospholipids that can influence the mechanisms of TAG crystallization in bulk milk fat (AMF). The thermal properties and crystallization behavior of milk fat in complex food products have been investigated because TAG crystals can impact the physical stability, texture, sensorial properties, and acceptability by the consumer.

Advances in neonatal nutrition: a step forward infant formula biomimetic of human milk structure and digestive behaviour. Conférence PPGAN UNIRIO

Le comportement alimentaire a un impact direct sur le bien-être et la santé, ainsi que sur des maladies associées à des désordres nutritionnels, notamment les maladies inflammatoires, les maladies chroniques du foie et de l’appareil digestif, et les cancers. En outre, les troubles alimentaires, en particulier la consommation excessive d’aliments ou d’alcool, le syndrome métabolique associé à l’obésité et les surcharges en fer sont directement responsables d’un nombre important de maladies chroniques, ou contribuent à leur morbidité. Les xénobiotiques, contaminants environnementaux et produits chimiques présents dans l’alimentation et médicaments, sont d’autres facteurs de risque des maladies aiguës et chroniques du foie et de l’intestin. L’objectif de l’unité « Nutrition, Métabolismes et Cancer » est d’étudier comment les déterminants alimentaires, comportementaux, environnementaux et métaboliques ont un impact sur la santé et les maladies chroniques de différents organes cibles tels que le foie, le système digestif et le cerveau. Le projet soutient une recherche translationnelle et clinique forte pour accélérer le transfert des avancées de la recherche cognitive pour le bénéfice des individus et des malades. L’unité réunit des experts en sciences sociales et comportementales, neurosciences, nutrition, hépatologie, gastroentérologie, cancérologie, physiologie, métabolisme, toxicologie, microbiologie, biologie moléculaire et cellulaire, et génomique.

The biological membrane surrounding fat globules in milk, the MFGM, is poorly known despite its importance in the functional properties of many dairy products and in the mechanisms of milk lipids digestion occurring in the gastrointestinal tract of mammal newborns. Studies recently revealed the formation of lipid domains in the MFGM that have been interpreted as the lateral segregation of high phase transition temperature (Tm) lipids, mainly milk sphingomyelin (MSM; Tm 34°C) [1]. The role played by these MSM-rich domains in the MFGM is currently unknown and needs further investigation. In this context, the aim of this study was to investigate the role of temperature and cholesterol in the morphology and nanomechanical properties of the MFGM. Accessing the biophysical properties of biological membranes at nanoscale is possible using Atomic Force Microscopy (AFM). In the complex biomimetic membranes formed using a MFGM lipid extract, topographical AFM images revealed for T < 35°C the formation of µm-large domains that protruded above the continuous phase by ~1 nm [2]. The resistance of the MSM-rich gel phase domains to rupture was significantly higher than that of the liquid disordered continuous phase, i.e. breakthrough force FB of 23 nN vs. 6 nN at 25°C, respectively. The key role played by cholesterol in the lateral segregation of high Tm lipids, by decreasing the size of the lipid domains, their height and by fluidizing the MFGM has been demonstrated [3]. Such work on the heterogeneous distribution of polar lipids in the MFGM may open perspectives in dairy technology and infant nutrition, e.g. optimisation of the interface of processed lipid droplets in infant milk formulas to mimick the biological MFGM in breast milk.

Within the dairy matrix, milk fat globules play a crucial role. How do they interact with other components of the matrix and what opportunities do they offer the dairy industry in terms of new product development?

Iron deficiency is usually the result of insufficient dietary intake of iron, poor utilization of iron from ingested food, or a combination of the two. Cow milk and dairy products are considered as poor in iron. Addition of supplementary iron to milk or dairy products might be an effective mean of increasing the dietary intake of iron for the population. This presentation reviews information on the iron fortification of milk and dairy products. It will be described the different possible iron sources with their advantages and inconvenient. Different results from the scientific literature will be reported showing that iron fortification of milk or dairy products induces several changes. Among the changes, special attentions will be paid on the 1. Bio-physico-chemical modifications of dairy constituents with the location of added iron after enrichment, the formations of iron-casein, iron-phosphopeptides, iron-whey-proteins and iron-phosphate. The oxidations of lipids and iron will be also described. 2. Modifications of some technological properties of milk enriched in iron (thermal stability of casein micelles, properties of acid and rennet gels made with milk); 3. Quality (composition, colour, flavour…) of some dairy products enriched in iron such as yoghurts, cheeses… and 4. Nutritional interest of iron enrichment. The last part of this presentation will show different dairy products fortified in iron and commercialised.

Lipids of human milk or infant formula convey most of the energy necessary to support the newborn growth. Until recently, infant formula chemical composition had been optimized but not their structure. And yet, more and more proofs of evidence have shown that lipids structure in human milk modulates digestion kinetics and is involved in metabolic programming. Indeed there is a striking difference of structure between human milk which is an emulsion based on dispersed milk fat globules (4 µm) secreted by the mammary gland and the submicronic neoformed lipid droplets (0.5 µm) found in infant formula. These droplets result from a series of operation units. This difference of structure modifies digestion kinetics and emulsion disintegration in the intestinal tract of the newborn. This difference persists along gastric phase which is mainly dominated by acid and enzyme-induced aggregation. Lipid droplets size is thus the key parameter to control gastric lipolysis, gastric emptying and intestinal lipolysis. This parameter also controls proteolysis since adsorbed proteins are more rapidly hydrolyzed than when in solution. In animal models, these differences of lipid structure would also impact digestive and immune systems’ maturation and microbiota. Lipid structure during neonatal period would also be involved in the early programming of adipose tissues and metabolism. The supplementation of infant formulas with bovine milk fractions (milk fat globule membrane extracts, triacylglycerol) or recent development of large droplets infant formula biomimetic of human milk lipid structure, along with new fields of innovation in neonatal nutrition, will be reviewed. Despite these recent innovations, more data on the structure of human milk throughout lactation and on the digestive behaviour of specific fractions of human milk lipids are still needed to build a sound basis for the optimization of infant formula. A better understanding of fractions that escape enzymatic digestion in the upper tract, and serve as substrates for microbiota, may help controlling microbiota shifts that exist between breast-fed and formula-fed infants. Combinations of factors (synbiotics and lipid structure) and more staging, seem important levers to further improve infant formula but their efficacy and safety still have to be assessed in clinical trials.

Ensuring adequate growth of preterm newborns remains a challenge. When breastfeeding is not possible, pasteurized human milk (PHM) from milk banks is preferentially administered to hospitalized newborns. Holder pasteurization (62.5°; 30 min) is applied for sanitary reasons but may reduce fat absorption through the inactivation of milk endogenous lipases. It has been suggested that homogenization of Holder-pasteurized human milk (PHM) could improve fat absorption and weight gain. The objective of the present work was to determine the impact of pasteurization and homogenization on gastric digestion in preterm infants. In a randomized controlled trial (NCT02112331), hospitalized tube-fed preterm infants were their own control to compare the gastric digestion of either i) raw (RHM) and pasteurized human milk (PHM), or ii) pasteurized (PHM) and homogenized PHM (PHHM). Over a six-day sequence, gastric aspirates were collected twice a day, before and 35, 60 or 90 min after the start of milk ingestion. The impact of homogenization on PHM digestive kinetics, lipolytic activity and disintegration was monitored. Pasteurization and homogenization affected milk initial structure, with the formation of protein aggregates at the interface of the milk fat globules in PHM and a six-fold increase of the specific surface (P

Polar lipids from milk are valuable sources to design affordable and biocompatible liposomes for food or medical applications. In particular, the milk sphingomyelin (MSM) that accounts for about 30 % wt of milk polar lipids exhibits a complex composition with over 95 % mol. of saturated acyl chains (C16:0, C22:0, C23:0 and C24:0) and a melting temperature (Tm) of 35°C. The mechanical properties of the liposome’s bilayer are important to ensure e.g. physical stability. The objective of this study was to investigate the mechanical properties of liposomes as a function of their chemical composition and physical state. Liposomes (diameter < 200 nm) were produced using controlled compositions of polar lipids and immobilized onto flat silicium substrate in aqueous environment. The elastic modulus E and bending rigidity kc of their bilayer were measured using atomic force microscopy (AFM). As references, liposomes made of dipalmitoylphosphatidylcholine in the gel phase (DPPC; C16:0 ; Tm= 41°C) was found to be about 9 times more elastic at 20°C than that of dioleoylphosphatidylcholine in the fluid phase (DOPC; C18:1n-9 ; Tm=-20°C). Surprisingly, MSM liposome bilayers exhibited intermediate mechanical properties to those of DPPC and DOPC, in spite of the presence of long and saturated acyl chains. Experiments performed with liposomes of synthetic C16:0-SM, C24:0-SM and C24:1-SM showed that chain length heterogeneity or unsaturation both contribute to decrease the overall elasticity of MSM liposomes. The results demonstrate the potential of AFM indentation to assess the mechanical properties of curved and soft nano-objects such as liposomes. They also show that biologically relevant liposomes with complex lipid compositions, such as MSM, exhibit overall softer elasticity than expected, probably because of altered lateral packing of the molecules in the gel phase. This study contributes in a better understanding of the mechanical properties of membranes as a function of their composition and physical state.

Dans les pays en développement, quels que soient le climat et lesespèces animales domestiquées, le lait et ses dérivés occupent leplus souvent une place importante dans la vie quotidienne et constituentun vecteur indéniable de développement. La diversité des pratiques,des outils et des produits nis est considérable et implique unensemble d’acteurs le long des chaînes d’approvisionnement. Parfoismenacés par les dynamiques en cours de la mondialisation, le lait etses dérivés représentent néanmoins une valeur patrimoniale inestimable.Outre leur rôle nutritif incontesté, ces produits ont souvent unrôle clé dans la microéconomie et le développement territorial, avecde multiples modèles selon les contraintes et les opportunités locales.L’objectif de ces rencontres, qui font suite à la 1re édition organisée àRennes (France) en 2014 (colloque6.inra.fr/lait2014), est de favoriser leséchanges d’expériences autour de la diversité des modèles de développementlaitier observés à l’échelle de la planète, de rassembler toutes lesinitiatives et réseaux impliqués, de mesurer l’importance des femmes etdes jeunes dans ces dynamiques et de m@ieux cerner le rôle des politiquespubliques pour accompagner cet essor.Aboutir ensemble à une meilleure coordination des actions autour dulait dans les pays en voie de développement, et notamment à des projetsconjoints de recherche, de formation ou d’appui est la principaleambition de ces rencontres.; Milk is an emulsion of fat droplets stabilized by a biological membrane called the milk fat globule membrane. The MFGM is mainly composed of polar lipids that have different melting temperatures (Tm), cholesterol, glycoproteins, and enzymes. The microstructure of the MFGM depends on the packing of polar lipids in the outer bilayer of the membrane that can lead to phase separation with formation of ordered domains [1]. This microstructure and the phase separation of lipids induced by the formation of domains are still poorly known despite its importance in dairy processing and in nutrition. Milk is usually submitted to changes in temperature e.g. storage (4-7°C), churning (10-12°C) and heat treatments (e.g. pasteurization). Do these temperature variations and thermal history of milk affect the packing of polar lipids in the plane of the MFGM?In this work,we characterized the evolution of the MFGM microstructure in situ, in milk as function of temperature and time by using confocal microscopy and Rh-DOPE as fluorescent probe.The dynamic of lipid domains was investigated on wide range of temperature (4-60°C) which includes the temperature of MFGM phase transition (gel/fluid; Tm = 36.4°C). The cooling kinetics from 60°C and storage duration at low temperature (4 or 20°C) affect the shape, the size and the number of lipid domains, through the mechanisms of nucleation and growth. On the other hand, heating kinetics show several responses of lipid domains such as diffusion, coalescence, reduction in size or disappearance at the surface of the fat globules [2]. We suggest also that the reaction of lipid domains to temperature changes can indicate its phase state (gel or ordered liquid) and the composition (presence of cholesterol). These structural changes can affect the interfacial properties of the MFGM with consequences on the functional properties of fat globules and on the digestion mechanisms.

International audience; In their native state, milk lipids are present in the form of dispersed droplets called Milk Fat Globules (MFG, average diameter of 4 µm in human and bovine milks) that have been recently pointed out as key elements of early nutritional programming. The native MFG is a unique biophysical element differing from other lipoproteic objects by its external trilayered membrane inherited from its secretory past. To play its major biological function, i.e. deliver energy to the mammal newborn, the MFG has to be hydrolyzed in the gastro-intestinal tract by lipases. This hydrolysis is typically a heterogeneous phase reaction, in which the lipase has to diffuse and get adsorbed onto the lipid phase before the formation of the enzyme-substrate complex, and the onset of the proper catalytic action. Very few techniques allow assessing the mechanism involved in the enzymatic hydrolysis of complex supramolecular substrates such as milk fat globules in emulsion. To get a better insight of this mechanism, 4-D imaging of gastric and pancreatic lipases enzymes using synchrotron SOLEIL UV fluorescence microscopy was applied. This methodology allowed mapping the adsorption and diffusion of lipases onto/within human or bovine MFG or biomimetic droplets devoid of membrane proteins. These data were completed with simultaneous transmission light imaging of MFG disintegration during hydrolysis. The high sensitivity of the DISCO beamline allowed detecting the auto-fluorescence of the digestive lipases, is a unique tool to unravel their mechanisms of adsorption onto complex substrate using free-label imaging and has generated useful data for infant formula optimization.

Propriétés fonctionnelles des lipides polaires laitiersC. Lopez (INRA-STLO, Rennes)Les lipides polaires majeurs du lait sont les glycérophospholipides PE, PC, PI, PS et les sphingolipides, majoritairement la sphingomyéline (SM). Les propriétés fonctionnelles des lipides polaires résultent de leur caractère amphiphile qui dirige leur organisation dans les membranes et aux interfaces. Leur tête polaire est très sensible aux ions (pH, calcium). La composition particulière de la SM, notamment la présence d’acides gras saturés à longue chaine, lui confère des propriétés spécifiques avec un changement d’état en fonction de la température (Tm 34°C) et des interactions avec le cholestérol. Dans les ingrédients préparés à partir de babeurre et de sérum de beurre, les lipides polaires laitiers sont organisés sous forme de fragments de membrane ou de vésicules. Il est également important de considérer que les ingrédients contenant des lipides polaires laitiers contiennent également d’autres constituants tels que les protéines, les minéraux et le lactose. Les propriétés fonctionnelles de ces ingrédients résultent de la combinaison des propriétés de ces différents constituants. Dans le WP3 du projet ANR Valobab (ANR-11-ALID-007), les partenaires INRA-STLO, ENILIA et Philolao ont investigué les propriétés fonctionnelles d’ingrédients contenant des lipides polaires.Les partenaires ENILIA et Philolao ont mis en place des tests standardisés visant à évaluer la capacité moussante (1% ingrédient) et la capacité émulsifiante (10% huile de tournesol, 0,5% ingrédient) de l’ingrédient produit dans le projet Valobab et d’ingrédients du commerce plus ou moins riches en lipides polaires d’origine laitière, végétale ou d’œuf. Dans les conditions expérimentales utilisées, l’ingrédient Valobab n’a pas de capacité moussante, par contre il a une très bonne capacité d’émulsification et permet de fabriquer des émulsions stables dans le temps.Le partenaire INRA-STLO a caractérisé la microstructure et les propriétés rhéologiques d’émulsions fabriquées avec l’ingrédient Valobab produit à Rennes (décrit dans Gassi et al., 2016). Dans les conditions expérimentales utilisées (20% MG, 4% ingrédient, pH de 6.7 à 4.6), il a été montré que cet ingrédient a d’excellentes propriétés émulsifiantes (Lopez et al., 2017). Les fragments de membrane des globules gras adsorbés à la surface des gouttelettes d’émulsion dirigent leurs propriétés interfaciales et contribuent à leur stabilité physique. Pour des pH < 5.5, il y a agrégation des gouttelettes d’émulsion et formation d’un gel avec une augmentation de la viscosité des émulsions. L’ingrédient et les émulsions préparées avec cet ingrédient sont très sensibles au pH et à l’environnement minéral. L’INRA-STLO a également montré que les lipides polaires laitiers permettent de moduler la microstructure et les propriétés rhéologiques d’émulsions contenant des protéines laitières, particulièrement pour pH < 5.5. En diminuant la connectivité entre les gouttelettes d’émulsion, les lipides polaires laitiers diminuent la viscosité des gels formés pour pH < 5.5. Les propriétés émulsifiantes d’ingrédients contenant des lipides polaires laitiers et des fragments de membrane des globules gras peuvent être utilisées dans diverses émulsions alimentaires, e.g. formules infantiles, crèmes, fromages, spreads, mais aussi dans les beurres et produits allégés en matière grasse.Références citées : Gassi et al. (2016) International Dairy Journal, 52, 26-34; Lopez et al. (2017) Food Research International, 91, 26-37.

Concentration en lipides polaires de babeurres. Journée de restitution du programme de recherche VALOBAB VALOrisation durable du BABeurre

The miscibility of milk sphingomyelin (milk-SM) and cholesterol was investigated in this study. Theeffect of different physical states of milk-SM on its interactions with cholesterol was determined bythe recording of isotherms of compression of Langmuir films for temperatures above and below thegel to La phase transition of milk-SM (Tm 34 C). For T = 15 C < Tm, the liquid expanded (LE) to liquidcondensed (LC) phase transition of milk-SM monolayers was observed at surface pressures of 10–15 mN/m. For T = 43 C > Tm, the milk-SM molecules were in a LE phase regardless of the surface pressureapplied. A phase diagram pressure – milk-SM/cholesterol composition was established. This studydemonstrated that both temperature and surface pressure affected the miscibility between the milk-SM and cholesterol. The strongest attractive forces (i.e. condensing effect) were identified for 30 mol%cholesterol when the milk-SM was in the LE phase state.

Sphingomyelin (SM) molecules are major lipid components of plasma membranes that are involved in functional domains. Among natural SMs, that found in milk (milk-SM) exhibits important acyl chain heterogeneities in terms of length and saturation, which could affect the biophysical properties and biological functions of the milk fat globule membrane or of liposome carriers. In this study, the thermotropic and mechanical properties of milk-SM, synthetic C16:0-SM, C24:0-SM and the binary mixtures C16:0-SM/C24:0-SM (50:50% mol) and C24:0-SM/C24:1-SM (95:5% mol) bilayer membranes were investigated using differential scanning calorimetry and atomic force microscopy, respectively. Results showed that acyl chain length, heterogeneity and unsaturation affected i) the temperature of phase transition of SM bilayers, and ii) the mechanical properties of liposome (diameter

Beyond fatty acid composition of milk fat that can impact the health of consumers, interest is growing regarding the importance of the supramolecular structure of milk lipids on their nutritional properties. Indeed, milk fat is found naturally under the form of an emulsion of lipid droplets called the milk fat globule (MFG) composed of a triglyceride core stabilized by a complex trilayered membrane called the MFG membrane. Recent researches have highlighted that this unique structure and the presence of bioactive lipids such as sphingomyelin could have a beneficial metabolic impact on lipid metabolism and contribute to intestinal and systemic health. The purpose of this chapter is to provide a focused overview on the composition of milk lipids, their organization as MFG and, their impact on lipid digestion and postprandial lipemia. In addition, the long-term effect on lipid metabolism and related metabolic players such as inflammation and gut microbiota are discussed.

Les lipides laitiers du lait maternel ou de formules infantiles fournissent la plupart de l’énergie disponible pour la croissance du nouveau-né. Jusqu’alors, la composition chimique des formules infantiles a été optimisée mais pas leur structure. Or il est de plus en plus démontré que la structure des lipides dans le lait maternel module les cinétiques de digestion et participe à la pré-programmation du métabolisme lipidique. Il existe en effet une différence majeure entre les émulsions natives de globules gras laitiers (4 μm) sécrétées par la glande mammaire et la structure des lipides dans les formules infantiles qui résultent d’une succession d’opérations unitaires de transformation et sont constituées de gouttelettes submicroniques (0.5 μm) avec des interfaces néoformées. Cette différence de structure modifie les cinétiques de digestion et de déstructuration des émulsions dans le tractus digestif des nouveau-nés. Ces cinétiques seront présentées sur différents types de formules infantiles commerciales ou modèles pouvant inclure des lipides laitiers (triacylglycérols ou extraits membranaires) et obtenues au cours de digestions in vitro simulant les conditions digestives chez le nouveau-né. Elles seront comparées aux cinétiques obtenues sur lait maternel in vivo ou in vitro. De façon générale, le lait maternel est lipolysé et protéolysé plus lentement que les émulsions transformées (modèles ou formules infantiles commerciales). La différence de structure initiale entre lait maternel et formules infantiles se maintient pendant toute la phase gastrique, qui est surtout dominée par des mécanismes d’agrégation acide. La taille des gouttelettes est le paramètre clé pour contrôler les lipolyses gastrique et intestinale et module également la vitesse de vidange gastrique néonatale. Ce paramètre contrôle également les cinétiques de protéolyse puisque les protéines adsorbées sont hydrolysées plus rapidement que les protéines solubilisées. La réintroduction d’extraits membranaires et de triacylglycérols issus de lait bovin dans les formules, permet de rapprocher les profils en acides gras libérés de ceux du lait maternel in vitro et module la physiologie digestive et le microbiote in vivo chez le porcelet. L’ensemble de ces résultats souligne le besoin de développer des traitements technologiques doux pour la fabrication de formules infantiles plus biomimétiques du lait maternel, comportant des globules gras préservés ou des structures lipidiques très analogues.

La microstructure de la membrane des globules gras du lait, et en particulier la séparation de phase des lipides qui induit la formation de microdomaines, sont peu connues malgré leur importance dans les propriétés fonctionnelles des globules gras et les mécanismes interfaciaux (e.g. interaction avec les enzymes digestives au cours de la digestion). La présence de microdomaines riches en sphingomyéline de lait (SM) a été montrée dans la membrane des globules gras de différents laits (humain, vache, bufflonne), à température ambiante [1]. Or, les globules gras peuvent subir des variations de températures: 4°C (stockage au froid), 37°C (digestion), 60°C (traitements thermiques).L’originalité de ce travail était de caractériser les évolutions structurales de la membrane des globules gras du lait en fonction de la température et de la durée de stockage. La microstructure de la membrane des globules gras a été observée, in situ dans le lait, par microscopie confocale en utilisant un phospholipide exogène comme sonde fluorescente (Rhodamine-DOPE).Les domaines riches en SM ont été observés à la surface des globules gras sur une large plage de températures (T : 4 – 60°C), qui inclue des températures inférieures et supérieures à la température de transition de phase phase gel – liquide des lipides polaires dans la membrane des globules gras (Tm = 36.4°C). Pour T > Tm, les domaines doivent correspondre à des complexes entre la SM et le cholestérol en phase liquide ordonnée Lo alors que pour T < Tm les domaines peuvent être en phase gel ou en phase Lo. Nous avons montré que des refroidissements rapides de T=60°C > Tm à T=20 – 4°C < Tm favorisent les mécanismes de nucléation avec la formation de nombreux petits domaines, et que le stockage favorise la croissance des domaines. Au cours du chauffage des laits, nous avons observé la diffusion des domaines, leur coalescence et leur diminution de taille jusqu’à disparition. Ces modifications de la microstructure de la membrane des globules gras peut avoir des conséquences en technologie laitière et dans les mécanismes de digestion des lipides du lait, notamment chez les nouveaux nés allaités.

Objectives and study: Hydrolysis of milk lipids is an essential step in their digestion, initiated in thedigestive tract by human gastric lipase (HGL). Although limited, gastric lipolysis has been presentedvery early as a key phenomenon in efficient fat digestion for newborns. It compensates for theimmaturity of exocrine pancreatic function and favours the subsequent action of other lipolyticenzymes such as pancreatic or bile salt dependant lipases (HPL and BSSL, respectively). Some valuesof HGL activity have been determined in gastric aspirates of infants in fasting state or postprandially.High variability was reported probably due to influence of the nature of the meal (infant formulaversus human milk), the age of the infant or the analysis method. However, in these studies the HGLoutput has never been estimated after administration of various types of human milk, nor thepotential contribution of non-gastric lipolytic enzymes. The objective of the present study is thus todetermine HGL activity, output and the contribution of other lipolytic enzymes in gastric aspirates ofpreterm infants in fasting state or after administration of raw, pasteurized or pasteurizedhomogenizedhuman milk.-Methods: In vivo study was conducted at Rennes Hospital on preterm infants fed by nasogastrictube (NCT02112331). The infants were included in two independent groups determining the type ofmeals: A) raw and pasteurized human milk; B) pasteurized and pasteurized-homogenized humanmilk. After collection (twice a day, six-day sequence), aspirates were immediately blended withglycerol (50:50 v/v) and frozen. Fasted gastric contents were collected three hours after last meal (upto 12 times per patient to verify intra-individual variation) and postprandial digesta at 35, 60 or 90min after administrated meal. Gastric volume and pH decrease were monitored. Lipolytic activity wasassessed by pH-stat at pH 6 (37°C) using tributyrin as substrate (as detailed by Gargouri et al., 1986),at least on triplicate. A subsequent determination at pH 8 allowed the estimation of non-gastriclipases contribution.-Results: Results evidenced high inter and intra-individual variability on estimated gastric lipolyticactivities. In the group A (n=12), lipolytic activity measured at pH 6 ranged from 2 up to 100 U/mL offasting gastric content. The determination at pH 8 revealed a contribution of non-gastric lipasesactivity ranging between 0 and 61%: as HGL is not active at such pH, a remaining activity will thusindicate the presence of BSSL or HPL. These contributions were higher in patients fed raw comparedto pasteurized human milk in both fasted and postprandial states, probably indicating: i) active BSSLfrom residual raw human milk contributed to gastric activity even three hours after meal; ii) thepresence of HPL (and hence intestinal content) in the stomach, which confirms the immaturity ofmotility function in preterms. In patients fed with pasteurized milk the lipolytic activity increasedwith postprandial time, indicating a HGL secretion induced by the meal. Lipolytic activities fromgroup B are currently been analyzed and will be further detailed.-Conclusion: This study presents a unique set of data illustrating the specificity of preterm infants’gastric digestive conditions. These data will be useful to develop relevant in vitro models of infantdigestion and analyze the link between gastric lipolytic activity and lipid digestion.

Objectives and study: The digestive functions are immature during the first months of life, especiallyfor preterm newborns (i.e. motility, enzymatic and secretory functions). The gastric digestion ofcomplex colloidal emulsions such as human milk and infant formulas is a key step which will furthermodulate nutrient absorption and infant nutrition. Factors such as gastric acidification, emptying rateand enzyme outputs are key parameters that play a role in the kinetics of hydrolysis and thedisintegration of these emulsions, and may be influenced by the nature of the meal and the age ofthe infant. The purpose of this study was to characterize gastric contents and physiologicalparameters of preterm infants in fasting state or after ingestion of raw, pasteurized or pasteurizedhomogenizedhuman milk.-Methods: In vivo study was conducted at Rennes Hospital on preterm infants fed by a nasogastrictube (NCT02112331). Newborns were included in two independent groups determining the type ofmeals: A) raw and pasteurized human milk; B) pasteurized and pasteurized-homogenized humanmilk. Gastric contents were collected twice a day, over six day. Gastric contents were collectedbefore meal ingestion and 35, 60 or 90 min after meal ingestion. Gastric volume and pH weremeasured. Lipase activity was determined by titration of released free fatty acids from tributyrin (pHstattechnique, at pH 6 and pH 8, at 37°C). Gastric emptying rates and ratio of meal to secretionswere determined using two different meal markers: total fatty acids for the lipid phase and taurinefor the liquid phase. The markers were quantified respectively by gas and cation-exchangechromatography.-Results: Infants from group A (n=12) were 16 to 53-day old at the first day of the study. On average(±SD), birth weight was 1.4 ± 0.3 kg and gestational age 29.6 ± 1.0 weeks. In group A, fasting gastricvolume was 1.4 ± 1.6 mL/kg of body weight and fasting pH was 3.7 ± 1.0 (range: 1.7 to 5.6). Gastricacidification was not impacted by meal (p > 0.05). On average, pH values of gastric digesta were 6.0 ±0.6, 5.2 ± 0.7 and 4.4 ± 0.8 at 35, 60 and 90 min after ingestion, respectively. These data confirm theneonates’ limited capacity of acidification but also suggest the impact of frequent feeding. Still ingroup A, at 35 min of digestion the gastric volume was higher for pasteurized than for raw humanmilk (p < 0.05). Similar trends were observed in group B and will be further discussed. Some lipaseactivity was measured in the fasting state; in postprandial aspirates the activity depended on themeal ingested. The estimation of gastric emptying rates and ratio of meal to secretions determinedby lipid or liquid markers is an original approach. Values differed depending on the marker, revealinga non-homogeneous emptying of the emulsion. It has been demonstrated (Marciani et al., 2007) thatemulsions that are destabilized in the gastric compartment can modulate the hormonal feedback(cholecystokinin).-Conclusion: This study presents a unique set of data illustrating the specificity of preterm infants’gastric digestive conditions. Understanding the physiological environment in the infant gastric tract isessential to optimize nutrition and oral drug delivery. Moreover, these data will be useful to developrelevant in vitro models of infant digestion.

The aim of the study was to determine the effect of maternal diets administered since day 1 of gestation and containing dairy lipids or vegetable oils differing in the supply of n-3 polyunsaturated fatty acids (n-3 PUFAs) (equilibrated or deficient) and of Lactobacillus fermentum (L. fermentum) on the docosahexaenoic acid (DHA) accretion in the pups at postnatal day 14 in the prefrontal cortex (PFC) and hippocampus (HC) for brain structures and in the liver and adipose tissue for peripheral tissues. Maternal milk fatty acid composition was also assessed by analyzing the fatty acid composition of the gastric content of the pups. DHA was higher in mice supplemented with L. fermentum than in mice in the deficient group in HC and PFC and also in liver and adipose tissue. This increase could be linked to the slight but significant increase in C18:3n-3 in the maternal milk. This proportion was comparable in the dairy lipid group for which the brain DHA level was the highest. L. fermentum may have a key role in the protection of the brain during the perinatal period via the neuronal accretion of n-3 PUFAs, especially during n-3 PUFA deficiency.

International audience; Milk is an emulsion of fat droplets stabilized by a biological membrane called the milk fat globule membrane (MFGM; Figure 1). The MFGM is mainly composed of polar lipids that have different melting temperatures (Tm), cholesterol, glycoproteins, and enzymes. The microstructure of the MFGM depends on the packing of polar lipids in the outer bilayer of the membrane that can lead to phase separation with formation of ordered domains (Figure 2). Milk is usually submitted to changes in temperature e.g. storage (4-7°C), churning (10-12°C) and heat treatments (e.g. pasteurization). Do these temperature variations and thermal history of milk affect the packing of polar lipids in the plane of the MFGM ? Experiments were performed by confocal laser scanning microscopy (CLSM) under temperature controlled conditions, using the head-labelled phospholipid fluorescent probe Rh-DOPE. Only the fluid phase of MFGM was labelled.

International audience; The milk fat globule membrane ( has recently gained a lot of attention, due to the growing interest in its nutritional and technological properties Its composition, rich in polar lipids, has great potential for new product applications with unique physical properties such as liposomes Milk polar lipids might be advantageous for both the stability and the biological acceptance of the formulation Milk polar lipids possess different structures of molecules saturated with high melting temperatures (Tm),in particular the milk sphingomyelin SM,Tm 35 C) or unsaturated with low Tm Does this difference in the molecular structure affect the mechanical properties of the membranes?

International audience; The enzymatic lipolysis of complex natural lipoproteic assemblies such as milk fat globules is central in neonatal digestion. This process first requires the rapid adsorption of a lipolytic enzyme, gastric lipase, onto the membrane enveloping the triglyceride substrate before the onset of catalytic activity. The interactions governing lipase adsorption onto this complex lipid/water interface are not fully elucidated. This study was designed to unravel the interactions of recombinant dog gastric lipase (rDGL) with model monolayers presenting liquid-liquid phase coexistence and mimicking the outer leaflet of the milk fat globule membrane. Combining biophysical tools (ellipsometry, tensiometry and atomic force microscopy), it was evidenced that rDGL partitions toward liquid expanded phase and at phase boundaries. rDGL gets adsorbed at several levels of insertion suggesting molecular cooperation that may favor insertion and strongly impacts on the lipid phase lateral organization. The addition of phosphatidylserine, negatively charged, reinforced adsorption; hence besides hydrophobic interactions and as further investigated through surface potential modeling, rDGL adsorption is favored by electrostatic interactions

Le 26 mai à Rennes, l'axe bio-imagerie de Biogenouest organise une journée dédiée aux lipides. Lors de cette journée, les plates-formes technologiques en bio-imagerie présenteront leurs techniques en prenant un exemple basé sur les lipides.Le 26 mai à Rennes, l'axe bio-imagerie de Biogenouest organise une journée dédiée aux lipides. Lors de cette journée, les plates-formes technologiques en bio-imagerie présenteront leurs techniques en prenant un exemple basé sur les lipides.; absent

Plusieurs équipes de recherche rennaises utilisent des expériences aux interfaces fluides planes pour connaître et comprendre les propriétés de biomolécules variées. Lors d’une journée d’échanges, des scientifiques de l'UMR STLO et d’autres équipes contribueront à dresser le panorama des thématiques concernées et montrer le potentiel de ces expériences. Une journée d'échanges scientifiques est organisée par l'Institut de Physique de Rennes, le 22 janvier 2015. Elle vise à illustrer le potentiel et à construire une vision d'ensemble des expériences aux interfaces planes, dans des domaines scientifiques aussi variés que la physique des mousses et émulsions, les technologies de transformation des aliments, la digestion néonatale des lipides laitiers ou l'interaction de protéines avec les membranes biologiques. L'opportunité de montrer que les expériences aux interfaces planes livrent des informations abondantes et pertinentes.Plusieurs équipes de recherche rennaises utilisent des expériences aux interfaces fluides planes pour connaître et comprendre les propriétés de biomolécules variées. Lors d’une journée d’échanges, des scientifiques de l'UMR STLO et d’autres équipes contribueront à dresser le panorama des thématiques concernées et montrer le potentiel de ces expériences.Une journée d'échanges scientifiques est organisée par l'Institut de Physique de Rennes, le 22 janvier 2015. Elle vise à illustrer le potentiel et à construire une vision d'ensemble des expériences aux interfaces planes, dans des domaines scientifiques aussi variés que la physique des mousses et émulsions, les technologies de transformation des aliments, la digestion néonatale des lipides laitiers ou l'interaction de protéines avec les membranes biologiques. L'opportunité de montrer que les expériences aux interfaces planes livrent des informations abondantes et pertinentes.; National audience; La lipolyse d’assemblages lipoprotéiques complexes tels que le globule gras laitier est très fréquente notamment durant la phase néonatale1. Cette lipolyse est initiée dans l’estomac par la lipase gastrique humaine qui agit à pH acide et possède des propriétés biochimiques et biophysiques uniques lui permettant d’initier l’attaque du globule gras, ce qui favorise ensuite l’action de la lipase pancréatique. La lipolyse est une réaction interfaciale qui nécessite avant la phase catalytique stricte une étape d’adsorption de la lipase gastrique sur cette interface2. Les interactions qui gouvernent l’adsorption de la lipase gastrique sur la membrane du globule gras ne sont pas totalement élucidées. L’objectif de ce travail était donc d’élucider ces interactions ainsi que la distribution latérale de la lipase gastrique dans des membranes modèles présentant une coexistence de phases identique à celle observée dans la membrane du globule gras. Une lipase gastrique recombinante de chien (rDGL) a été utilisée comme modèle à la lipase gastrique humaine. Une combinaison d’outils biophysiques de la plateforme BioMIF (ellipsométrie, tensiométrie et microscopie de force atomique) a été mise en œuvre pour caractériser l’adsorption de la rDGL dans les membranes modèles3. Des films de Langmuir ont été utilisés pour imiter le feuillet extérieur de la membrane du globule gras. Des mélanges de glycérophospholipides et extraits de babeurre présentant différentes phases physiques, charges de surface et densités moléculaires ont permis d’identifier les interactions enzyme/membrane gouvernant l’adsorption. Nous avons montré que: 1.La rDGL présente une forte affinité pour les interfaces lipide/liquide. Néanmoins, si une grande partie des molécules est proche de l’interface un nombre restreint de molécules s’insère à l’interface. 2. La rDGL s’adsorbe préférentiellement dans la phase liquide expansée et aux frontières des deux phases, l’adsorption se fait à trois niveaux de profondeur dans la membrane (h1~5.5 nm, h2

Plusieurs équipes de recherche rennaises utilisent des expériences aux interfaces fluides planes pour connaître et comprendre les propriétés de biomolécules variées. Lors d’une journée d’échanges, des scientifiques de l'UMR STLO et d’autres équipes contribueront à dresser le panorama des thématiques concernées et montrer le potentiel de ces expériences. Une journée d'échanges scientifiques est organisée par l'Institut de Physique de Rennes, le 22 janvier 2015. Elle vise à illustrer le potentiel et à construire une vision d'ensemble des expériences aux interfaces planes, dans des domaines scientifiques aussi variés que la physique des mousses et émulsions, les technologies de transformation des aliments, la digestion néonatale des lipides laitiers ou l'interaction de protéines avec les membranes biologiques. L'opportunité de montrer que les expériences aux interfaces planes livrent des informations abondantes et pertinentes.Plusieurs équipes de recherche rennaises utilisent des expériences aux interfaces fluides planes pour connaître et comprendre les propriétés de biomolécules variées. Lors d’une journée d’échanges, des scientifiques de l'UMR STLO et d’autres équipes contribueront à dresser le panorama des thématiques concernées et montrer le potentiel de ces expériences.Une journée d'échanges scientifiques est organisée par l'Institut de Physique de Rennes, le 22 janvier 2015. Elle vise à illustrer le potentiel et à construire une vision d'ensemble des expériences aux interfaces planes, dans des domaines scientifiques aussi variés que la physique des mousses et émulsions, les technologies de transformation des aliments, la digestion néonatale des lipides laitiers ou l'interaction de protéines avec les membranes biologiques. L'opportunité de montrer que les expériences aux interfaces planes livrent des informations abondantes et pertinentes.; National audience

The microstructure of milk fat in processed dairy products is poorly known despite its importance in their functional, sensorial and nutritional properties. However, for the last 10 years, several research groups including our laboratory have significantly contributed to increasing knowledge on the organization of lipids in situ in dairy products. This paper provides an overview of recent advances on the organization of lipids in the milk fat globule membrane using microscopy techniques (mainly confocal microscopy and atomic force microscopy). Also, this overview brings structural information about the organization of lipids in situ in commercialized milks, infant milk formulas and various dairy products (cream, butter, buttermilk, butter serum and cheeses). The main mechanical treatment used in the dairy industry, homogenization, decreases the size of milk fat globules, changes the architecture (composition and organization) of the fat/water interface and affects the interactions between lipid droplets and the protein network (concept of inert vs active fillers). The potential impacts of the organization of lipids and of the alteration of the milk fat globule membrane are discussed, and technological strategies are proposed, in priority to design biomimetic lipid droplets in infant milk formulas.

Milk lipids supply most of the calories necessary for newborn growth in maternal milk or infant formulas. The chemical composition of infant formulas has been optimized but not the structure of the emulsion. There is still a major difference between the native emulsions of milk fat globules and processed submicronic emulsions in infant formulas. This difference may modify the kinetics of digestion of emulsions in newborns and influence lipid metabolism. To check this, semi-dynamic gastric in vitro digestions were conducted on three matrices: a standardized milk emulsion containing native milk fat globules referred to as minimally-processed emulsion and two processed model infant formulas (homogenized or homogenized/pasteurized). Gastric conditions mimicked those reported in newborns. The minimally-processed emulsion was lipolyzed and proteolyzed slower than processed formulas. The difference in initial structure persisted during digestion. The surface of the droplets was the key parameter to control gastric lipolysis kinetics, the pattern of released fatty acids and proteolysis by faster hydrolysis of adsorbed proteins.

International audience; The interfacial quality of emulsions impacts their digestibility. Infant formulas are stabilized by milk proteins and non-dairy tensioactives whereas Human milk is stabilized by a native membrane based on Milk Polar Lipids (MPL) and proteins. The addition of MPL in infant formulas seems a clever approach to closely mimic Human milk natural interface although very few infant formulas use milk lipids more expensive than vegetable lipids. The interfacial composition of such emulsion has never been characterized nor its effect on emulsion digestibility. Our study aimed at elucidating these two points. Two model emulsions with similar droplets size (mode=2 µm, specific surface~15 m2/g of lipids) and based on a blend of vegetable fats (3 g/100 g) were produced at labscale: the emulsions were stabilized by MPL and milk proteins (molar ratio=1:1); MPL were introduced before homogenization in emulsion MPL1 to favour their interfacial contribution whereas MPL were introduced after homogenization in emulsion PROT1. The emulsions structures and interfacial compositions were characterized by laser granulometry, confocal laser scanning microscopy and high performance liquid chromatography. The emulsions were then digested using a dynamic in vitro model of neonatal digestion [1,2]. The interface of MPL1 contained 0.32 % of total MPL/m2 of emulsion surface area whereas only 0.06-0.12 % of total MPL/m2 occupied the interface of PROT1. No selectivity in the adsorption of MPL was reported. The protein interfacial coverage was twice lower in MPL1. For both emulsions a selective adsorption of caseins (α-s and β in particular) was observed. The digestive desintegration and kinetics of lipolysis and proteolysis of the emulsions in the gastric phase were affected by these interfacial differences: the structure of MPL1 was more stable and its hydrolysis slightly slower.

National audience; Le globule gras natif de lait de mammifère constitue un objet biophysique unique se démarquant des autres objets lipoprotéiques (oléosome, lipoprotéines…) notamment par sa membrane tricouche héritée du mécanisme de sécrétion du globule [1,2]. Au niveau de ses fonctions biologiques le globule gras natif est avant tout vecteur d’énergie via son cœur de triglycérides qui fournit 50-60 % des calories nécessaires au développement du nouveau-né de mammifère [3] Afin d’assurer ce rôle énergétique le globule gras est hydrolysé au niveau de la lumière gastro-intestinale. La première phase de cette hydrolyse est catalysée par la lipase gastrique humaine. Les questions qui sont encore aujourd’hui posées concernent d’une part l’organisation structurale de la membrane externe [4] et d’autre part les mécanismes d’action de la lipase sur cet objet. Notre approche est de reconstruire le feuillet externe de la membrane lipidique en utilisant les films de Langmuir comme modèle membranaire et d’utiliser la microscopie à force atomique afin d’obtenir des informations fines d’organisation moléculaire. Ainsi nous avons mis en évidence l’hétérogénéité de la membrane reconstituée à partir des éléments natifs purifiés. Dans la suite de ce travail, l’affinité de la lipase gastrique pour cette membrane a été quantifiée, sur à la fois des systèmes lipides simplifiés (DOPC, DPPC) et sur les systèmes reconstitués ‘naturels’. Pour conclure, au travers de nos résultats nous avons mis en évidence une localisation préférentielle de la lipase sur la membrane avec des taux d’insertion très faibles pour une présence protéique importante. La suite de ce travail est de mettre en évidence des effets des traitements technologiques sur la structuration de la membrane qui seront alors susceptibles d’induire des modifications d’activité de la lipase gastrique.

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Ce séminaire scientifique montre l’orientation nouvelle des recherches menées au sein de l’UMR STLO en termes de technologie des procédés laitiers. L’éco-conception est la ligne directrice de ce séminaire. Le programme est : Eco-conception : définitions et démarches développées au STLO Présentation de la Plateforme INRA pour l‘analyse multicritère de la durabilité (Means) Mise en place d'une démarche d'éco-conception dans les itinéraires technologiques : cas dans le domaine du fractionnement de protéines et lipides laitiers Intérêt de l'instrumentation dans une démarche d'éco-conception : Cas d’un atelier de concentration-séchage idéal Caractérisation du procédé d’évaporation sous vide: démarche et intérêts Intérêt de la modélisation dans l'éco-conception : cas de l'évaporation sous vide.

Session : Nutrition & EndoscopySession : Nutrition & Endoscopy; Presence of milk phospholipids and milk lipids modified the immunomodulatory properties of infant formula in neonatal pigs. 4th World Congress of Pediatric Gastroenterology, Hepatology and Nutrition

Introduction et But de l’étude. – Les procédés de transformation appliqués aux matières premières telles que le lait peuvent engendrer des modifications de structure des principaux constituants. Par exemple, le traitement thermique du lait provoque des interactions entre les protéines et les autres constituants de la matrice (lipides, sucres) entrainant l’apparition d’agrégats thermo-induits, de composés de Maillard… La susceptibilité de ces structures néoformées à être digérées par le nourrisson et la nature des peptides bioactifs libérés au niveau intestinal par leur hydrolyse a été très peu étudiée jusqu’alors. L’objectif de ce travail était donc de déterminer l’impact de deux paramètres technologiques (couple temps/température, pourcentage d’extrait sec du lait avant traitement thermique) considérés comme essentiels dans la fabrication de formules infantiles sur la digestion des caséines et en particulier sur leur aptitude à résister au tractus digestif. Matériel et Méthodes. – Six échantillons de poudres ont été fabriqués en atelier pilote en soumettant un lait à 25 % ou 35 % d’extrait sec à trois types de traitements thermiques classiquement utilisés en industrie (80 °C/20 s, 85 °C/180s, 105 °C/60s). Les six échantillons produits plus un 7e n’ayant reçu aucun traitement thermique (témoin négatif) ont été caractérisés (taille des particules, composition globale) puis soumis à un modèle statique in vitro de digestion. Le modèle utilisé consistait en trois phases : une phase gastrique de 60 min à pH 3 en présence de pepsine porcine, suivie d’une phase duodénale de 30 min à pH 6,5 en présence de trypsine porcine, chymotrypsine bovine et sels biliaires puis d’une incubation de 15 min avec des vésicules de la bordure en brosse de l’épithélium intestinal de porc. Les pHs et teneurs en enzymes et sels biliaires ont été choisis pour correspondre à ceux physiologiquement retrouvés chez le nourrisson. Les formules infantiles digérées avec ce modèle ont été analysées en électrophorèse SDS-PAGE et par technique ELISA et western-blotting en utilisant une collection de 22 anticorps monoclonaux spécifiques de différents épitopes des caséines \alphas1, \alphas2, \beta et \kappa. Les peptides générés en fin de phase duodénale et intestinale ont été identifiés par spectrométrie de masse. Résultats. – Les régions \alphas1(f133-151), \alphas1(f185-199), \alphas2(f36-75), \beta(1-25) et \beta(76-93) ont été montrées comme les plus résistantes à la digestion et ce, quel que soit le procédé de transformation utilisé. Ces régions correspondent à des zones phosphorylées des caséines ou très hydrophobes au pH gastrique et donc peu accessibles aux protéases. Le traitement thermique du lait modifie toutefois les profils peptidiques obtenus en fin de digestion. Conclusions. – Ces résultats renforcent l’idée qu’à termes, en maitrisant les procédés de fabrication des formules infantiles, on doit pouvoir orienter la production de peptides bioactifs dans l’intestin.