The Experts below are selected from a list of 19623 Experts worldwide ranked by ideXlab platform
Sophie Gallier - One of the best experts on this subject based on the ideXlab platform.
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modification of milk fat Globules during processing and gastrointestinal digestion
2020Co-Authors: Sophie Gallier, Harjinder SinghAbstract:Milk is an important source of nutrition in the diet of children and adults. Our understanding of the structure of the milk fat Globules and the effect of dairy processing on the digestion of lipids has increased over the last decades. The role of the milk fat globule membrane (MFGM) has moved beyond being simply a triglyceride-stabilizing membrane and is recognized for providing efficient digestion, gut maturation and protection and brain development. This chapter reviews the structure of the MFGM, the effect of processing on the structure of the fat Globules and impact on their digestion under adult and infant conditions, and the development of emulsions mimicking the structure of milk fat Globules.
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Nature's complex emulsion: The fat Globules of milk
Food Hydrocolloids, 2017Co-Authors: Harjinder Singh, Sophie GallierAbstract:Abstract The milk fat globule in milk represents a unique emulsion system designed by Nature to deliver energy, essential fatty acids and lipid-soluble nutrients to the neonate. The fat Globules range from 0.1 to 15 μm in diameter and are stabilised by milk fat globule membrane (MFGM) which is composed of phospholipids, various glycoproteins, enzymes and cholesterol. Extensive knowledge on the intracellular origin, composition and structure of fat Globules and MFGM has been accumulated over the last 30 years. Recently, it has been speculated that the MFGM has profound effects on the accessibility of the triglycerides for lipase-catalysed digestion. This has initiated a large number of studies on the digestion of milk fat Globules in various dairy systems involving both in vitro and in vivo human digestion models. In addition, the identification of health-beneficial components of MFGM has led to increasing interest in developing MFGM as a food ingredient with unique functional properties and health benefits. This review focuses on recent knowledge on composition and structure of fat Globules, the MFGM, and the behaviour of fat Globules during gastro-intestinal digestion. MFGM ingredients and their applications are briefly discussed.
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a novel infant milk formula concept mimicking the human milk fat globule structure
Colloids and Surfaces B: Biointerfaces, 2015Co-Authors: Sophie Gallier, Karin Vocking, J A Post, Bert J M Van De Heijning, Dennis Acton, Eline M. Van Der Beek, Ton Van BaalenAbstract:Human milk (HM) provides all nutrients to support an optimal growth and development of the neonate. The composition and structure of HM lipids, the most important energy provider, have an impact on the digestion, uptake and metabolism of lipids. In HM, the lipids are present in the form of dispersed fat Globules: large fat droplets enveloped by a phospholipid membrane. Currently, infant milk formula (Control IMF) contains small fat droplets primarily coated by proteins. Recently, a novel IMF concept (Concept IMF) was developed with a different lipid architecture, Nuturis®, comprising large fat droplets with a phospholipid coating. Confocal laser scanning microscopy (CLSM), with appropriate fluorescent probes, and transmission electron microscopy were used to determine and compare the interfacial composition and structure of HM fat Globules, Concept IMF fat droplets and Control IMF fat droplets. The presence of a trilayer-structured HM fat globule membrane, composed of phospholipids, proteins, glycoproteins and cholesterol, was confirmed; in addition exosome-like vesicles are observed within cytoplasmic crescents. The Control IMF fat droplets had a thick protein-only interface. The Concept IMF fat droplets showed a very thin interface composed of a mixture of phospholipids, proteins and cholesterol. Furthermore, the Concept IMF contained fragments of milk fat globule membrane, which has been suggested to have potential biological functions in infants. By mimicking more closely the structure and composition of HM fat Globules, this novel IMF concept with Nuturis® may have metabolic and digestive properties that are more similar to HM compared to Control IMF.
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Chemical and structural characterisation of almond oil bodies and bovine milk fat Globules
Food Chemistry, 2012Co-Authors: Sophie Gallier, Keith C. Gordon, Harjinder SinghAbstract:Abstract Lipids in almonds are present as oil bodies in the nut. These oil bodies are surrounded by a membrane of proteins and phospholipids and are a delivery vehicle of energy in the form of triglycerides, similarly to the more studied bovine milk fat globule membrane. Chemical, physical and microscopic analyses revealed major differences in the composition and structure of almond oil bodies and bovine milk fat Globules. The lipids of both natural emulsions differed in degree of unsaturation, chain length, and class. The almond oil body membrane does not contain any cholesterol or sphingomyelin unlike the bovine milk fat globule membrane. Therefore, the phospholipid distribution at the surface of the oil bodies did not present any liquid-ordered domains. The membranes, a monolayer around almond oil bodies and a trilayer around bovine fat Globules, may affect the stability of the lipid droplets in a food matrix and the way the lipids are digested.
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composition of bovine milk fat Globules by confocal raman microscopy
International Dairy Journal, 2011Co-Authors: Rafael Jimenezflores, Sophie Gallier, Keith C. Gordon, David W. EverettAbstract:Confocal Raman microscopy was used to determine the chemical fingerprint of individual bovine milk fat Globules of different sizes and from milk sourced from different breeds. No detectable level of triglycerides was found in the small milk fat Globules of 1 μm diameter or less in size. These small fat Globules also delivered information about the lipids of the milk fat globule membrane. In addition, the lipid composition varied according to the size of the Globules with an increasing concentration of carotenoids and decreasing level of unsaturation with increasing diameter. The carotenoids content also varied according to the breed origin of the milk, with Jersey milk fat Globules containing more carotenoids than the Friesian-Jersey milk fat Globules. The results suggest that the milk fat Globules have different properties according to their size.
Harjinder Singh - One of the best experts on this subject based on the ideXlab platform.
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modification of milk fat Globules during processing and gastrointestinal digestion
2020Co-Authors: Sophie Gallier, Harjinder SinghAbstract:Milk is an important source of nutrition in the diet of children and adults. Our understanding of the structure of the milk fat Globules and the effect of dairy processing on the digestion of lipids has increased over the last decades. The role of the milk fat globule membrane (MFGM) has moved beyond being simply a triglyceride-stabilizing membrane and is recognized for providing efficient digestion, gut maturation and protection and brain development. This chapter reviews the structure of the MFGM, the effect of processing on the structure of the fat Globules and impact on their digestion under adult and infant conditions, and the development of emulsions mimicking the structure of milk fat Globules.
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symposium review fat Globules in milk and their structural modifications during gastrointestinal digestion
Journal of Dairy Science, 2019Co-Authors: Harjinder SinghAbstract:The fat Globules in milk are unique oil droplets that are stabilized by a specific and structurally complex membrane, the milk fat globule membrane (MFGM). In the last decade, excellent progress has been made on studying the structure of the milk fat Globules and the MFGM and how common processing treatments affect these structures to deliver dairy products with improved functional properties. Although the digestion of milk fat to deliver energy and lipid-soluble nutrients is essential for survival of the neonate, there is little understanding of the complex processes involved. The structural alterations to fat Globules during gastrointestinal processing affect the way in which milk fat is digested, absorbed, and metabolized. The packaging of these Globules within the MFGM or in other forms may affect the bioaccessibility of raw or processed milk fat Globules; in turn, this may affect access of the gastrointestinal enzymes to the Globules and, therefore, may influence the rate and extent of lipid digestion. This review focuses on recent advances in understanding milk fat Globules during gastrointestinal digestion, including the effects of processing on their bioavailability and the kinetics of lipid digestion. Possible effects of the dairy matrix on lipid digestion and physiological responses are briefly described.
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Nature's complex emulsion: The fat Globules of milk
Food Hydrocolloids, 2017Co-Authors: Harjinder Singh, Sophie GallierAbstract:Abstract The milk fat globule in milk represents a unique emulsion system designed by Nature to deliver energy, essential fatty acids and lipid-soluble nutrients to the neonate. The fat Globules range from 0.1 to 15 μm in diameter and are stabilised by milk fat globule membrane (MFGM) which is composed of phospholipids, various glycoproteins, enzymes and cholesterol. Extensive knowledge on the intracellular origin, composition and structure of fat Globules and MFGM has been accumulated over the last 30 years. Recently, it has been speculated that the MFGM has profound effects on the accessibility of the triglycerides for lipase-catalysed digestion. This has initiated a large number of studies on the digestion of milk fat Globules in various dairy systems involving both in vitro and in vivo human digestion models. In addition, the identification of health-beneficial components of MFGM has led to increasing interest in developing MFGM as a food ingredient with unique functional properties and health benefits. This review focuses on recent knowledge on composition and structure of fat Globules, the MFGM, and the behaviour of fat Globules during gastro-intestinal digestion. MFGM ingredients and their applications are briefly discussed.
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Chemical and structural characterisation of almond oil bodies and bovine milk fat Globules
Food Chemistry, 2012Co-Authors: Sophie Gallier, Keith C. Gordon, Harjinder SinghAbstract:Abstract Lipids in almonds are present as oil bodies in the nut. These oil bodies are surrounded by a membrane of proteins and phospholipids and are a delivery vehicle of energy in the form of triglycerides, similarly to the more studied bovine milk fat globule membrane. Chemical, physical and microscopic analyses revealed major differences in the composition and structure of almond oil bodies and bovine milk fat Globules. The lipids of both natural emulsions differed in degree of unsaturation, chain length, and class. The almond oil body membrane does not contain any cholesterol or sphingomyelin unlike the bovine milk fat globule membrane. Therefore, the phospholipid distribution at the surface of the oil bodies did not present any liquid-ordered domains. The membranes, a monolayer around almond oil bodies and a trilayer around bovine fat Globules, may affect the stability of the lipid droplets in a food matrix and the way the lipids are digested.
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proteolysis of milk fat globule membrane proteins during in vitro gastric digestion of milk
Journal of Dairy Science, 2011Co-Authors: Aiqian Ye, Harjinder SinghAbstract:The influence of gastric proteolysis on the physicochemical characteristics of milk fat Globules and the proteins of the milk fat globule membrane (MFGM) in raw milk and cream was examined in vitro in simulated gastric fluid (SGF) containing various pepsin concentrations at pH 1.6 for up to 2 h. Apparent flocculation of the milk fat Globules occurred in raw milk samples incubated in SGF containing pepsin, but no coalescence was observed in either raw milk samples or cream samples. The changes in the particle size of the fat Globules as a result of the flocculation were dependent on the pepsin concentration. Correspondingly, the physical characteristics of the fat Globules and the composition of the MFGM proteins in raw milk changed during incubation in SGF containing pepsin. The major MFGM proteins were hydrolyzed at different rates by the pepsin in the SGF; butyrophilin was more resistant than xanthine oxidase, PAS 6, or PAS 7. Peptides with various molecular weights, which altered with the time of incubation and the pepsin concentration, were present at the surfaces of the fat Globules.
Marie-caroline Michalski - One of the best experts on this subject based on the ideXlab platform.
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Membrane phospholipids and sterols in microfiltered milk fat Globules
European Journal of Lipid Science and Technology, 2007Co-Authors: Caroline Fauquant, Nadine Leconte, Michel Guichardant, Valérie Briard-bion, Marie-caroline MichalskiAbstract:Native milk fat Globules of various mean diameters, ranging from d43 = 2.3 mm to 8.0 mm, were obtained using microfiltration of raw whole milk. After milk fat globule washing, the milk fat globule membrane (MFGM) was separated by manual churning. After total lipid extraction and separation of polar lipids, their phospholipid (PL) and sterol composition was measured using thin-layer chromatography, methyl ester analyses by gas chromatography, and gas chromatography coupled to mass spectrometry. The main PL species were phosphatidylethanolamine, phosphatidylcholine and sphingomyelin. The respective fatty acid composition of each PL species was measured. Many different minor bioactive sterols were detected in the MFGM, e.g.lanosterol, lathosterol, desmosterol, stigmasterol and b-sitosterol. No significant differences in the PL and sterol profile were found between MFGM extracted from small and large milk fat globule fractions.
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cla profile in native fat Globules of different sizes selected from raw milk
International Dairy Journal, 2005Co-Authors: Marie-caroline Michalski, Pierre JuanedaAbstract:Abstract The CLA content and isomer profile were characterized among two subclasses of the native milk fat Globules. The latter corresponded to two fractions obtained by a microfiltration process using Spring mixed milk, leading to small fat Globules (SFG; d 32 ∼ 2.8 μ m ) in the microfiltrates and large ones (LFG; d 32 ∼ 5 μ m ) in the retentates. Relatively, SFG always contained more CLA than the LFG originating from the same mixed milk, though discrepancies among different milk samples were observed. The main CLA isomer was the cis -9, trans -11, the content of which tended to increase when the native milk fat globule size decreased (from 82.2% to 87.3% of total CLA isomers). Consequently, the SFG contained less trans -12, trans -14; trans -11, trans -13; trans -11, cis -13 and trans -8, cis -10 isomers than the corresponding LFG. However, the relative variation of some isomers between small and large fat globule from the same milk varied depending on milk origin and the potential of fat globule fractionation for influencing the content and distribution of CLA seems to be limited.
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Differently sized native milk fat Globules separated by microfilftration: fatty acid composition of the milk fat globule membrane and triglyceride core
European Journal of Lipid Science and Technology, 2005Co-Authors: Caroline Fauquant, Nadine Leconte, Valérie Briard-bion, Marie-caroline MichalskiAbstract:The aim of this study was to characterize the fatty acid composition of the core and membrane of differently sized milk fat Globules separated by microfiltration, which can now be used to manufacture dairy products. Native milk fat Globules of various mean diameters, ranging from d43 = 2.3 µm to 8.0 µm, were obtained using microfiltration of raw whole milk. After milk fat globule washing, the milk fat globule membrane (MFGM) and the triglyceride core (TC) were separated by manual churning. After total lipid extraction from each fraction, their fatty acid composition was characterized using methyl ester analysis by gas chromatography. Regardless of season, no significant differences were observed in the fatty acid composition of the MFGM phospholipids. Conversely, significant differences were found in the fatty acid composition of TC; particularly, small fat globule TC contained more medium-chain fatty acids and less stearic acid than large fat globule TC. These results show that the previously observed differences in total fatty acid composition among differently sized milk fat Globules are due to their triglyceride composition and MFGM amount rather than to the composition of the MFGM.
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The size of native milk fat Globules affects physico-chemical and functional properties of Emmental cheese
Le Lait, 2004Co-Authors: Marie-caroline Michalski, Nadine Leconte, Valérie Briard, Françoise Michel, Henri Goudedranche, Benedicte Camier, Jean-yves Gassi, Jacques FauquantAbstract:Emmental cheeses were produced using either small (~3 $\mu$m, SFG) or large (~6 $\mu$m, LFG) native milk fat Globules obtained by a patented microfiltration process. Ripened SFG cheeses were less flexible and less firm than LFG cheeses. Indeed, the SFG cheeses contained more moisture and underwent greater proteolysis than the LFG cheeses 52 d after manufacture. However, lipolysis was three-fold lower in SFG cheeses. This was linked to the milk fat structure in Emmental cheese: larger inclusions of denuded destabilized fat were observed in LFG cheeses, whereas more fat Globules were observed in SFG cheeses. One Emmental cheese was produced using homogenized milk fat Globules, in which lipolysis was dramatically increased and unacceptable. For a given size range, the structure of milk fat is thus of tremendous importance regarding lipolysis and small natural milk fat Globules cannot be replaced by homogenized ones. The melting temperature and solid fat content of fat in Emmental cheese increased with native fat globule size. This is related to the improved functional properties of SFG cheeses, i.e., increased stretching, elastic increase and melting, and lower extrusion force compared with LFG cheeses. This study confirms, as previously pioneered using Camembert cheese manufacturing technology, that the use of native milk fat Globules with different sizes can lead to a range of new dairy products with different physico-chemical and functional properties.
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Native fat Globules of different sizes selected from raw milk: thermal and structural behavior
Chemistry and Physics of Lipids, 2004Co-Authors: Marie-caroline Michalski, Nadine Leconte, Valérie Briard-bion, Michel Ollivon, Christelle LopezAbstract:The aim of this study was to characterize differences in the thermal and structural behavior between different sized native milk fat Globules. A novel microfiltration process permits the selection of native small fat Globules (SFG, 1–3 m) and large fat Globules (LFG, >5 m) in raw milk, that were analyzed by X-ray diffraction (XRD) coupled to differential scanning calorimetry (DSC). There were no major differences in triglyceride crystalline structures between SFG and LFG, after eliminating thermal history and the influence of cooling rates. The three main 3L and 2L crystalline structures appearing under slow cooling existed regardless of globule size. The supercooling increased for the SFG, mainly due to heterogeneous nucleation in winter milk, and also to compositional variations in spring milk. Differences appeared regarding stabilized crystalline forms at 20 ◦C and subsequent cooling: the SFG contained less 2L triglyceride structures than the LFG. These results can be important in dairy manufactures using tempering periods.
Peter S Kim - One of the best experts on this subject based on the ideXlab platform.
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a specific hydrophobic core in the alpha lactalbumin molten globule
Journal of Molecular Biology, 1998Co-Authors: Peter S KimAbstract:Molten Globules are partially structured protein folding intermediates that adopt a native-like overall backbone topology in the absence of extensive detectable tertiary interactions. It is important to determine the extent of specific tertiary structure present in molten Globules and to understand the role of specific side-chain packing in stabilizing and specifying molten-globule structure. Previous studies indicate that a small degree of specific side-chain packing stabilizes the structures of the cytochrome c, apomyoglobin, and staphylococcal nuclease molten Globules. Here we investigate the extent of specific side-chain packing in the molten globule of α-lactalbumin (α-LA), a highly fluctuating, non-cooperatively formed molten globule. By analyzing a set of point mutations in the helical domain of α-LA, we have identified a stabilizing hydrophobic core. Moreover, this core corresponds to a previously identified structural subdomain and likely contains some native-like packing interactions. Our results suggest that native-like packing of core amino acids helps stabilize molten Globules and that some specific interactions can exist in even highly dynamic, fluctuating species.
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different subdomains are most protected from hydrogen exchange in the molten globule and native states of human α lactalbumin
Journal of Molecular Biology, 1995Co-Authors: Brenda A Schulman, Zhengyu Peng, Christina Redfield, Christopher M. Dobson, Peter S KimAbstract:Abstract α-Lactalbumin (α-LA) is a two-domain, calcium-binding protein that forms one of the best studied molten Globules. We present here amide hydrogen exchange studies of the molten globule formed by human α-LA at pH 2 and compare these results with a similar study of the native state at pH|nlbsb|6.3. The most persistent structure in the molten globule is localized in the helical domain, consistent ith previous results. However, the helices most protected from hydrogen exchange in the molten globule are, in the native state, less protected from exchange than other regions of the protein. The molten globule appears to contain major elements of the native fold, but formation of the fully native state requires stabilization of structure around the calcium-binding site and domain interface.
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bipartite structure of the alpha lactalbumin molten globule
Nature Structural & Molecular Biology, 1995Co-Authors: Zhengyu Peng, Peter S KimAbstract:Molten Globules are thought to be general intermediates in protein folding. Apparently conflicting studies have failed to clarify whether one of the best characterized molten Globules, that of alpha-lactalbumin, resembles an expanded native-like protein or a nonspecific collapsed polypeptide. Here we show that the molten globule properties of alpha-lactalbumin are largely confined to one of its two domains. The alpha-helical domain forms a helical structure with a native-like tertiary fold, while the beta-sheet domain is largely unstructured. Molten Globules thus possess a native-like backbone topology, but this topology does not necessarily encompass the entire polypeptide chain. Our studies indicate that molten Globules provide an approximate solution to, and considerable simplification of the protein folding problem.
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local structural preferences in the alpha lactalbumin molten globule
Biochemistry, 1995Co-Authors: Zhengyu Peng, Peter S KimAbstract:Molten Globules have been proposed to be general intermediates in protein folding. Despite numerous studies, a detailed description of the structure of a molten globule remains elusive. Recently, we showed that the molten globule formed by the helical domain of alpha-lactalbumin (alpha-LA) has a native-like backbone topology. Here we probe local structural preferences in the helical domain of the alpha-LA molten globule by analyzing a set of native and nonnative single disulfide bond variants using a combination of circular dichroism spectroscopy and determination of the equilibrium constant for disulfide bond formation. We find that the region surrounding the 28-111 disulfide bond has a high preference to adopt a native-like structure. Formation of other native or nonnative disulfide bonds is significantly less favorable. Our results suggest that molten Globules contain regions with varying degrees of specificity for native-like structure and that the core region surrounding the 28-111 disulfide bond plays an important role in alpha-LA folding by stabilizing the molten globule intermediate.
Christelle Lopez - One of the best experts on this subject based on the ideXlab platform.
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The size and interfacial composition of milk fat Globules are key factors controlling triglycerides bioavailability in simulated human gastro-duodenal digestion
Food Hydrocolloids, 2014Co-Authors: Cyrielle Garcia, Benoît Robert, Christelle Lopez, Claudine Antona, Martine ArmandAbstract:Lipids organisation might modulate fatty acid bioavailability leading to health implications. We determined whether the size and the interfacial composition of cow milk fat Globules could affect triglycerides digestibility. Native fat Globules of various sizes covered by their biological membrane (4.2 mm, large LFG 6.6 mm, small SFG 1.7 mm) or homogenised heat-treated (0.3 mm) were digested in gastric and duodenal conditions simulating human physiology. Lipolysis extents were calculated from the amount of free fatty acids generated, and the fatty acid composition of the products of lipolysis was determined by GC analysis. SFG were more efficiently hydrolysed than LFG by gastric (13.3 versus 5.6%), gastric plus pancreatic (62.9 versus 48.7%) and pancreatic (79.6 versus 54.7%) lipases. A higher lipid interface area with native SFG, that might increase lipases binding sites, can explain these results. However, the homogenisation, which markedly decreases fat globule size increasing consequently the lipid/water interface area, did not improve gastric (9%) or duodenal (64.5%) lipolysis probably due to an important change in globule surface composition (proteins versus phospholipids). Interestingly, the size of the milk globule (SFG and HM versus NM and LFG) controls the type of the free fatty acids generated by the human gastric lipase, palmitic versus oleic acid, suggesting a different orientation of the accessible mixed triglycerides. Moreover, the type of monoglycerides produced from SFG digestion could be less atherogenic compared to LFG. The size of fat Globules governs gastric and duodenal lipolysis extent when the composition of the interfacial layer is appropriate. It might further control fatty acid bioavailability impacting on gastric emptying rate via the preferential release of oleic acid, a strong stimulator of CCK.
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milk fat Globules enveloped by their biological membrane unique colloidal assemblies with a specific composition and structure
Current Opinion in Colloid and Interface Science, 2011Co-Authors: Christelle LopezAbstract:Abstract Milk fat Globules are the natural colloidal assemblies secreted by the mammary epithelial cells to provide lipids and other bioactive molecules in the gastrointestinal tract of newborns. They are also consumed by human adults in food products such as cream and cheeses. These biological entities (about 4 μm diameter) have a complex architecture composed of a core rich in triacylglycerols (TAGs) enveloped by a biological membrane, the milk fat globule membrane (MFGM). Although their utmost importance for infants and their functional and nutritional role in dairy products, milk fat Globules remain the least understood aspect of milk. This paper provides an overview of recent knowledge with emphasis on milk fat globule origin, size heterogeneities, fatty acid and TAG composition. The crystallisation properties are reported. Recent studies focusing on the MFGM including characterisation of its composition, probing of its structure, and accumulation of scientific evidence of MFGM nutritional and health properties are also discussed. The unique composition and structure of milk fat Globules leading to specific functionalities are highlighted.
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fat Globules selected from whole milk according to their size different compositions and structure of the biomembrane revealing sphingomyelin rich domains
Food Chemistry, 2011Co-Authors: Christelle Lopez, Jacques Fauquant, Nadine Leconte, Eric Beaucher, Valerie Briardbion, Olivia Menard, Florence Rousseau, Benoît RobertAbstract:Abstract Milk fat Globules are unique delivery systems for biologically active molecules in the gastrointestinal tract. However, their properties have not yet been fully investigated. In this study, we performed a comparative analysis of the polar lipid and fatty acid compositions of milk fat Globules as a function of their size and investigated the structure of the milk fat globule membrane (MFGM). An optimised process of microfiltration was used to select the small milk fat globule (SMFG; 1.6 μm) fractions and the large milk fat globule (LMFG; 6.6 μm) fractions from the same initial whole milks (4.2 μm). The SMFG-fractions contained significantly (i) higher amounts of polar lipids, 8.9 ± 0.9 vs 2.7 ± 0.3 mg/g fat for LMFG-fractions and 6.3 ± 0.5 mg/g fat for whole milks, (ii) lower relative proportions of phosphatidylcholine and sphingomyelin in the MFGM, (iii) higher amounts of C12:0, C14:0, C16:0, C18:1 trans , C18:2 c9 tr11, and lower amounts of C18:0 and C18:1 c9 than did LMFG-fractions and whole milks. Whatever the size of native milk fat Globules, the biophysical characterisation performed in-situ , using confocal laser scanning microscopy, showed heterogeneities in the MFGM. The lateral segregation of sphingomyelin in rigid liquid-ordered domains, surrounded by the fluid matrix of glycerophospholipids in the liquid-disordered phase, was revealed. The heterogeneous distribution of glycolipids and glycoproteins was also observed in the MFGM. A new model for the structure of the MFGM is proposed and discussed. The physical, chemical and biological consequences, (i) of the differences in milk fat globule compositions according to their size and (ii) of the specific structure of the MFGM due to sphingomyelin remain to be elucidated.
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Native fat Globules of different sizes selected from raw milk: thermal and structural behavior
Chemistry and Physics of Lipids, 2004Co-Authors: Marie-caroline Michalski, Nadine Leconte, Valérie Briard-bion, Michel Ollivon, Christelle LopezAbstract:The aim of this study was to characterize differences in the thermal and structural behavior between different sized native milk fat Globules. A novel microfiltration process permits the selection of native small fat Globules (SFG, 1–3 m) and large fat Globules (LFG, >5 m) in raw milk, that were analyzed by X-ray diffraction (XRD) coupled to differential scanning calorimetry (DSC). There were no major differences in triglyceride crystalline structures between SFG and LFG, after eliminating thermal history and the influence of cooling rates. The three main 3L and 2L crystalline structures appearing under slow cooling existed regardless of globule size. The supercooling increased for the SFG, mainly due to heterogeneous nucleation in winter milk, and also to compositional variations in spring milk. Differences appeared regarding stabilized crystalline forms at 20 ◦C and subsequent cooling: the SFG contained less 2L triglyceride structures than the LFG. These results can be important in dairy manufactures using tempering periods.
