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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Effects of Microfluidization and Homogenization on the Composition and Structure of Liposomal Aggregates from Whey Buttermilk and Commercial Buttermilk

Nguyen, Tracey Mai T 01 August 2013 (has links)
Milk derived ingredients from the production of cheese and butter can be used as vehicles for nutrients. Buttermilk is a nutritious product of milk that comes from the churning of cream into butter. One of the advantages of buttermilk is that it is enriched in milk fat globule components, such as phospholipids and forms emulsions with fat when treated with high shear. The objective of this work was to explore the effects of shear on regular buttermilk and whey buttermilk in terms of liposomal aggregate size and chemical composition. The effects of microfluidization at 2000 psi and homogenization at 2000 psi/500 psi on the particle size distribution of liposomal aggregates between whey buttermilk (WBM) at pH 4.6 and 6.8 and commercial sweet buttermilk (SBM) at pH 4.60 were compared with whey protein isolate (WPI) at pH 4.6. At pH 6.80, WPI and SBM are too soluble in water to measure particle size but WBM is not as soluble. From this investigation, the mean particle diameter of the SBM aggregates at pH 4.6 decreased after the first pass through the microfluidizer and the same is true, after homogenization. SBM aggregates at pH 4.6 had a significantly larger mean particle diameter before treatments in both shear processes compared to WPI at pH 4.6 and WBM at pH 4.6 and WBM at pH 6.8 (p < 0.0001). WPI at pH 4.6 and WBM at both pH showed no significant differences in their mean particle size in both homogenized and microfluidized treatments. WPI and SBM samples resulted in significant particle diameter differences vi from before to after homogenizing at pH 4.6. SBM at pH 4.6 had significantly larger average particle diameter than WBM at pH 4.6 (p < 0.0002), WPI at pH 4.6 (p < 0.0002) and WBM at pH 6.8 (p < 0.0045) before microfluidization at pass 0. WBM and WPI across all treatments showed very similar tendencies in small particle size attributes and some similarities in protein composition. In addition, the small aggregate size of WBM is suggested to be influenced by the presence of phospholipids and thus, creating significantly smaller mean particles compared to SBM even before inducing high shear. In contrast, treated and untreated SBM differed from WBM in phospholipid composition in both homogenization and microfluidization techniques. WBM samples contained more phospholipids than SBM, whereas WPI samples contained very low concentrations of phospholipids. Through HPLC analysis, WPI, SBM, and WBM showed different profiling of the phospholipid classes. These differences may be due structural changes of the aggregates from shearing, initial thermal treatments or hydrophobic and/or protein-phospholipid interactions between the aggregates. SBM samples also exhibited different protein profiling than WBM and WPI samples. This study suggests that high shear and presence of phospholipids impact the size distribution of liposomal aggregates through structural alterations. The aggregates can be utilized as a novel ingredient and in the processing of dairy foods to deliver nutrition.
2

F4ac-fimbrial-binding proteins in porcine milk and the absorption of colostral proteins by piglets

Huang, Yanyun 13 November 2008
F4 positive enterotoxigenic Escherichia coli (ETEC) is the most common pathogen causing neonatal diarrhea in piglets. The pathogenesis requires the attachment of ETEC to the intestinal brush border, mediated by F4 fimbria. Colostral anti-F4 antibodies and some non-immunoglobulin porcine skim milk proteins can bind F4 and prevent colonization and infection by F4-positive ETEC. Little is known, however, about the F4-binding ability of porcine milk fat globule membrane (MFGM) proteins. In addition, the knowledge of the absorption of porcine colostral proteins into the blood of neonatal piglets is limited, despite the well accepted concept that in neonatal piglets, protein absorption from the intestine is non-selective.<p> In this study, the ability of porcine MFGM proteins to bind purified F4ac (one of the three subtypes of F4 fimbriae) was investigated. Porcine MFGM proteins were first separated by 2D SDS-PAGE and subsequently identified by mass spectrometry. Overlay western Blot was then employed to demonstrate the interaction between porcine MFGM proteins and purified F4ac. Several proteins from porcine MFGM reacted with F4ac, and of these, lactadherin, butyrophilin, adipophilin, and acyl-CoA synthetase 3 reacted strongly. The biological function of these proteins in vivo was not investigated but it is possible that their interaction with F4ac positive ETEC interferes with bacterial attachment and colonization. In order to investigate protein absorption by neonatal piglets after natural suckling, the protein profiles of the plasma of pre-suckling and 24 h post-suckling neonatal piglets were studied by 2D SDS-PAGE. Those plasma proteins that increased prominently after suckling were then identified by mass spectrometry. Only immunoglobulins were unequivocally determined to be absorbed, because they were absent before suckling and present in large quantity in plasma 24 h after suckling. The absorption of other colostral proteins was either equivocal or not detectable by our detection methods. These results suggest that, unlike immunoglobulins, major non-immunoglobulin proteins in porcine colostrum may not be absorbed into systemic circulation in substantial amounts.
3

F4ac-fimbrial-binding proteins in porcine milk and the absorption of colostral proteins by piglets

Huang, Yanyun 13 November 2008 (has links)
F4 positive enterotoxigenic Escherichia coli (ETEC) is the most common pathogen causing neonatal diarrhea in piglets. The pathogenesis requires the attachment of ETEC to the intestinal brush border, mediated by F4 fimbria. Colostral anti-F4 antibodies and some non-immunoglobulin porcine skim milk proteins can bind F4 and prevent colonization and infection by F4-positive ETEC. Little is known, however, about the F4-binding ability of porcine milk fat globule membrane (MFGM) proteins. In addition, the knowledge of the absorption of porcine colostral proteins into the blood of neonatal piglets is limited, despite the well accepted concept that in neonatal piglets, protein absorption from the intestine is non-selective.<p> In this study, the ability of porcine MFGM proteins to bind purified F4ac (one of the three subtypes of F4 fimbriae) was investigated. Porcine MFGM proteins were first separated by 2D SDS-PAGE and subsequently identified by mass spectrometry. Overlay western Blot was then employed to demonstrate the interaction between porcine MFGM proteins and purified F4ac. Several proteins from porcine MFGM reacted with F4ac, and of these, lactadherin, butyrophilin, adipophilin, and acyl-CoA synthetase 3 reacted strongly. The biological function of these proteins in vivo was not investigated but it is possible that their interaction with F4ac positive ETEC interferes with bacterial attachment and colonization. In order to investigate protein absorption by neonatal piglets after natural suckling, the protein profiles of the plasma of pre-suckling and 24 h post-suckling neonatal piglets were studied by 2D SDS-PAGE. Those plasma proteins that increased prominently after suckling were then identified by mass spectrometry. Only immunoglobulins were unequivocally determined to be absorbed, because they were absent before suckling and present in large quantity in plasma 24 h after suckling. The absorption of other colostral proteins was either equivocal or not detectable by our detection methods. These results suggest that, unlike immunoglobulins, major non-immunoglobulin proteins in porcine colostrum may not be absorbed into systemic circulation in substantial amounts.
4

Anticarcinogenic and Immunomodulatory Properties of the Milk Fat Globule Membrane

Zanabria Eyzaguirre, Romina 10 May 2013 (has links)
The milk fat globule membrane (MFGM) obtained from bovine milk is a source of bioactive compounds. In this research, the hypothesis that the MFGM possesses anticarcinogenic capacity and immune modulatory properties was tested, along with the hypothesis that processing history of the fat globules will affect the bio-functionality of the MFGM. Throughout all experiments, lipopolysaccharide (LPS) was minimized by extracting the milk using a catheter, working under aseptic conditions and avoiding contamination via reagents. To study the anticarcinogenic capacity, native MFGM was tested in vitro using two colon adenocarcinoma cell lines (HT-29, Caco-2). Stimulated cells showed a dose-dependent decrease in cell proliferation, starting at very low concentrations (1 μg/mL based on protein) and its efficiency was comparable or even superior to the commercial anticarcinogenic drugs melphalan and C2-ceramide. Cytotoxicity and apoptosis were found to be mechanisms responsible for this bioactivity, as shown by the lactate dehydrogenase enzyme activity and the increase in caspase-3 production. MFGM- immune modulatory capacity was also tested by studying its effects on splenocyte proliferation, apoptosis and cytokine production. While splenocyte proliferation was not affected when the MFGM isolate was used alone, it suppressed cell division in the presence of polyclonal activators (LPS, Concanavalin A) used to simulate inflammatory conditions. Cytokine production suggests inhibition of the splenocytes’ activation process as the mechanism behind its bioactivity. Milk heating caused a significant decrease in bioactivity, indicating that protein interactions and denaturation as well as the structural changes caused by this treatment, directly affect the MFGM bio-functionality. Partial hydrolysis (by trypsin and phospholipase-A2) caused a similar effect, suggesting that not only the phospholipids are involved in the anticarcinogenic capacity, but also, the complex mixture of proteins which form part of the MFGM complete system. In summary, the bioactivity of the MFGM extracted from milk is not limited to its anticarcinogenic but also to its immune regulatory ability, by helping control the response of the immune system when inflammatory conditions arise. However, pre-treatment of the raw material greatly affects this bioactivity, suggesting that greater care may be needed in processing of fat globules to maintain such important characteristics of their components. / Canadian Dairy Council (CDC), Ontario Dairy Council (ODC), Natural Sciences and Engineering Research Council of Canada (NSERC).
5

Mjölkfettkulemembran : och dess effekter på träning hos vuxna människor. / Milk fat globule membrane

Konstantino Egerfors, Catrin January 2018 (has links)
Konsumtion av kosttillskott i samband med träning är något som ökat i Sverige de senaste åren. Det är främst produkter med högt proteininnehåll som konsumeras, även om behovet av extra protein är under diskussion. Men det kan finnas andra ämnen med positiv påverkan på träning. Exempelvis mjölkfettkulemembran (MFGM) som är en viktig del av bröstmjölk då det bland annat verkar bidra till spädbarnets kognitiva utveckling. Senare studier på möss har visat att MFGM tycks ha positiva effekter på träning. Syftet med denna litteraturstudie var därför att undersöka om MFGM även har positiva effekter på människor i samband med träning. Artiklar togs fram genom sökning i databasen PubMed. Artiklarna skulle undersökt effekten av MFGM på människors träning för att inkluderas, samt vara randomiserade, dubbelblindade och placebokontrollerade. Totalt inkluderades fem studier. Samtliga studier visade på positiva effekter av MFGM i samband med träning, dock skiljde sig resultaten mellan studierna beroende på vilken effekt MFGM hade. Om MFGM har någon effekt på styrka är fortfarande oklart då resultaten är oeniga, däremot kan det tänkas att rörlighet och neuromuskulär utveckling förbättras av ett tillskott av MFGM, men ytterligare studier behövs för att bekräfta detta. / Consumption of dietary supplements associated with exercise has increased in Sweden the last couple of years. It is mainly products with high protein that are consumed, although the need for additional protein is questionable. However, there may be other substances with positive effects on exercise. For example milk fat globule membrane (MFGM) which is an important part of breast milk that seems to contribute to infant's cognitive development. Studies on mice have shown that MFGM seems to have positive effects on exercise. The purpose of this literature study was therefore to investigate whether MFGM also has positive effects on humans in combination with exercise. Articles for this study was selected by searching the PubMed database. The articles were included if they were studying the effect of MFGM on exercise on humans, they also had to be randomized, double blinded and placebo-controlled. A total of five studies were included. All studies showed positive effects of MFGM combined with exercise, however, the results differed between studies in terms of what kind of effect. If MFGM has any effect on strength is still unclear since the results varies. Agility and neuromuscular development may be improved by a dietary supplement of MFGM, but further studies are needed to confirm this.
6

Monitoring Heat-Induced Conformational Changes and Binding of Milk Fat Globule Membrane and β-lactoglobulin using Quartz Crystal Microbalance with Dissipation

Fishel, Simone 22 December 2022 (has links)
No description available.
7

Effects of Milk Processing on the Milk Fat Globule Membrane Constituents

Elías-Argote, Xiomara E 01 July 2011 (has links)
ABSTRACT Effects of Milk Processing on the Milk Fat Globule Membrane Constituents Xiomara E. Elías-Argote The milk fat globule membrane (MFGM) is avidly studied by many groups of scientists around the world due to its unprecedented nutritional and functional properties; however, limited research has been performed on the effects of milk processing on the chemical changes of the MFGM. Thus, this study highlights the changes that lipids and proteins undergo from the time milk leaves cow’s udders. Cooling (4 °C) was included along with subsequent pasteurization by different traditional thermal processes and cold pasteurization by pulse light ultra violet treatment. Cooling milk to 4 °C had a measureable effect on the MFGM composition, resulting in protein alterations, particularly to butyrophilin and adipophilin. Thermal treatments disturbed the native structures of molecules and increased the adsorption of milk and whey proteins on the globules, especially a-lactalbumin and b-lactoglobulin. As the heat intensity increased, the aggregation of fat globules became more pronounced due to protein interactions. Intrinsic MFGM proteins also varied in relative abundance during the processing steps. The concentrations of polar lipids did not change during processing, with the exception of phosphatidylserine, which decreased during the cooling and thermal treatments. Cold pasteurization (UV treatment) had a minimal effect on fat globules and MFGM proteins. Since the MFGM promises to deliver nutritional effects and more when included in food products, currently HTST pasteurization was shown to be the best method to process milk and obtain MFGM isolates for further supplementation.
8

Dietary Milk Fat Globule Membrane Reduces the Incidence of Aberrant Crypt Foci in Fischer-344 Rats and Provides Protections Against Gastrointestinal Stress in Mice Treated with Lipopolysaccharide

Snow, Dallin R. 01 December 2010 (has links)
Milk fat globule membrane surrounds the fat droplets of milk. It is a biopolymer containing primarily membrane glycoproteins and polar lipids which contribute to its properties as a possible neutraceutical. The aims of the studies were to determine if dietary milk fat globule membrane: (1) confers protection against colon carcinogenesis; and (2) promotes gut mucosal integrity while decreasing inflammation compared to diets containing corn oil or anhydrous milk fat. Aim 1. Three dietary treatments differing only in the fat source were formulated: (1) AIN-76A, corn oil; (2) AIN-76A, anhydrous milk fat; and (3) AIN-76A, 50% milk fat globule membrane, 50% anhydrous milk fat. Each diet was formulated to contain 50 g/kg diet of fat and to be identical in macro and micro nutrient content. To assess protection against colon carcinogenesis, male, weanling Fischer-344 rats were randomly assigned to one of the three dietary treatments. Animals were injected with 1,2-dimethylhydrazine once per week at weeks 3 and 4. After 13 weeks animals were sacrificed, colons were removed, and aberrant crypt foci were counted by microscopy. Rats fed the milk fat globule membrane diet (n = 16) had significantly fewer aberrant crypt foci (20.9 ± 5.7) compared to rats fed corn oil (n = 17) or anhydrous milk fat (n = 16) diets (31.3 ± 9.5 and 29.8 ± 11.4 respectively; P < 0.05). Aim 2. Male BALB/c mice were randomly assigned to one of two diets: AIN- 76A, corn oil or AIN-76A, 50% milk fat globule membrane, 50% anhydrous milk fat. After 5 weeks mice were injected with saline vehicle control or lipopolysaccharide and gavaged with dextran-FITC. To assess gut mucosal integrity and inflammation, serum samples were assayed for dextran-FITC 24 and 48 hours after gavage, and a panel of 16 cytokine concentrations was analyzed. Serum concentrations of IL-6, IL-10, IL-17, MCP-1, IFNγ, and TNFα decreased and gut permeability decreased 45% in lipopolysaccharide challenged mice fed milk fat globule membrane diet compared to control diet at 24 hours (P < 0.05). Overall, the results of these aims suggest that diets containing milk fat globule membrane are protective against colon carcinogenesis, inhibit the inflammatory response, and protect against gastrointestinal stress.
9

Obtenção de ingrediente lacteo enriquecido em lipideos polares a partir de leitelho de soro / Obtention of dairy ingredient enriched in polar lipids from whey buttermilk

Costa, Marcela de Rezende 12 September 2008 (has links)
Orientadores: Mirna Lucia Gigante, Rafael Jimenez-Flores / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-09-11T21:12:34Z (GMT). No. of bitstreams: 1 Costa_MarceladeRezende_D.pdf: 1269005 bytes, checksum: be9b972dd7766eba5cc6917dd666c5f0 (MD5) Previous issue date: 2008 / Resumo: O leitelho de soro é um subproduto do processamento de manteiga a partir do creme de soro. Esse subproduto lácteo contém fragmentos da membrana do glóbulo de gordura do leite (MGGL), material rico em componentes com funções nutricionais e efeitos benéficos à saúde, destacando-se os fosfolipídeos. O objetivo desse trabalho foi obter um ingrediente lácteo enriquecido em fosfolipídeos da MGGL a partir do leitelho de soro utilizando a associação de duas tecnologias de fracionamento: ultrafiltração e extração com fluido supercritico (EFS). O leitelho de soro foi submetido à ultrafiltração e a cinco diafiltrações a 25 °C e o retentado obtido foi seco em spray-dryer, obtendo-se o leitelho de soro em pó (LSP), o qual foi submetido a três ciclos de extração a 50 °C com dióxido de carb ono supercrítico. As matériasprimas, produtos finais e uma amostra comercial de leitelho tradicional em pó (LTP) foram analisados quanto a sua composição centesimal, teor de fosfolipídeos, perfis lipídico e protéico. Os leitelhos de soro em pó, submetidos ou não à EFS, e o LTP foram avaliados quanto ao tamanho de partículas e suas propriedades funcionais (solubilidade protéica e capacidade emulsificante) em pH 5 e 7. A filtração em membrana reduziu em 74 e 96% os teores de lactose e cinzas no retentado e aumentou os de proteínas, lipídeos e fosfolipídeos em 91, 190 e 300%, respectivamente. A EFS reduziu em 55,4% o teor de lipídeos, removendo exclusivamente lipídeos apolares, com isso aumentou em 71% o teor de fosfolipídeos no leitelho de soro em pó, resultando em um produto com 73% de proteínas, 21% de lipídeos, 3% de lactose, 3% de cinzas e 12% de fosfolipídeos, em base seca. As propriedades funcionais dos leitelhos de soro em pó, submetidos à extração supercrítica (LSP-EFS) ou não (LSP), foram pouco ou não afetadas pelo pH, enquanto o abaixamento de pH prejudicou as características do LTP, devido ao alto teor de caseínas nesse tipo de pó em relação aos de leitelhos de soro. Os pós em soluções (5% de proteína) apresentaram de 69 a 84% de suas partículas, em % volumétrica, entre 10 e 100 µm. A solução de LTP em pH 5 foi a que apresentou a maior quantidade de partículas acima de 100 µm. LSP e LSP-EFS apresentaram solubilidades protéicas em torno de 86 e 84%, respectivamente, independente do pH. O LTP teve a solubilidade reduzida de 86 para 73% quando o pH foi reduzido de 7 para 5. Em pH 7, as emulsões (20% óleo de canola, 1% proteína) de LSP e de LSPEFS apresentaram melhor estabilidade (IC de 0,2 e 0,4%, respectivamente) do a emulsão de LTP (IC de 3,0%). Em pH 5, a emulsão de LSP-EFS foi a que mostrou melhor estabilidade, apresentando um IC de 7%, valor cerca de 82% menor do que os das emulsões de LSP e LTP. Os leitelhos de soro em pó obtidos podem ser considerados ingredientes com características promissoras, associando propriedades tecnológicas, especialmente para uso em alimentos de baixo pH, e conteúdo de compostos potencialmente benéficos à saúde, principalmente após o tratamento com extração supercrítica / Abstract: OBTENTION OF DAIRY INGREDIENT ENRICHED IN POLAR LIPIDS FROM WHEY BUTTERMILK. Whey buttermilk is a by-product from the whey cream processing into butter. This dairy by-product contains milk fat globule membrane (MFGM) fragments, a material rich in components with nutritional functions and beneficial health effects, especially phospholipids. The objective of this research was obtaining a dairy ingredient enriched in MFGM phospholipids from whey buttermilk using the association of two fractionation technologies: ultrafiltration and supercritical fluid extraction (SFE). Whey buttermilk was submitted to ultrafiltration and five diafiltrations at 25 °C. The retentate was spray-dried and later s ubmitted to three cycles of extraction at 50 °C with supercritical carbon dioxi de. Raw materials, final products and a commercial traditional buttermilk powder sample (BMP) were analyzed for gross composition, lipid and protein profiles, and phospholipids content. Whey buttermilk powders, before and after the SFE, and the BMP had particle size and some functional properties (protein solubility and emulsifying capacity) evaluated in pH 5 and 7. Membrane filtration reduced in 74 and 96% lactose and ash contents in the retentate and increased proteins, lipids and phospholipids in 91, 190 and 300%, respectively. SFE reduced in 55.4% the lipids content, removing exclusively non-polar lipids, while increased in 71% the phospholipids content in whey buttermilk powder, resulting in a product with 73% of proteins, 21% of lipids, 3% of lactose, 3% of ash and 12% of phospholipids, in dry matter basis. Functional properties of the whey buttermilk powders, treated (WBP-SFE) or not through SFE (WBP), were little or not affected by pH, while dropping the pH impaired the BMP features, due the high casein content in this type of powder in relation to the ones from whey buttermilk. The powders in solutions (5% protein) presented from 69 to 84% of the particles, in volume%, between 10 and 100 µm. The BMP solution in pH 5 was the one with the biggest amount of particles above 100 µm. WBP and WBP-SFE showed protein solubilities around 86 and 84%, respectively, independent of pH. BMP had the solubility reduced from 86 to 73% when pH was reduced from 7 to 5. In pH 7, the emulsions (20% canola oil, 1% protein) of the WBP and the WBP showed better stability (CI of 0.2 and 0.4%, respectively) than the BMP emulsion (CI of 3.0%). When in pH 5, WBP-SFE emulsion had the best stability, presenting CI of 7%, value about 82% smaller than the ones of WBP and BMP emulsions. Whey buttermilk powders obtained in this work can be considered ingredients with promising features, combining technological properties, especially for use in low pH foods, and content of components with potential health benefits, mainly after the supercritical extraction treatment / Doutorado / Doutor em Tecnologia de Alimentos
10

The milk fat globule membrane: physico-chemical studies and its techno-functional valorisation in buttermilk

Vanderghem, Caroline 04 June 2009 (has links)
Vanderghem Caroline. (2009). La membrane du globule gras du lait : études physico-chimiques et sa valorisation technofonctionnelle dans les babeurres (Thèse de doctorat en Anglais). Gembloux, Belgique, Faculté Universitaire des Sciences Agronomiques de Gembloux. 198p., 14 tabl., 59 fig. Résumé La membrane du globule gras du lait (MGGL) est une structure complexe qui enveloppe, protège et délivre des composants bioactifs et des nutriments dune façon efficace au nouveau-né. Sa structure est unique par rapport à dautres systèmes biologiques de transport de lipides. Lobjectif général de ce travail a été de contribuer à augmenter les connaissances et la compréhension de cet émulsifiant naturel. La première partie de cette thèse concerne létude de la structure de la MGGL. Limportance des protéines membranaires concernant la stabilité et leur disposition dans la MGGL ont été étudiés. Les protéines de la MGGL sont présentes en petite quantité dans le lait et une technique de pré-fractionnement simpose afin de les isoler par rapport aux autres protéines du lait (caséines et protéines du lactosérum). Une technique dextraction qui a été développée dans notre laboratoire a été testée afin disoler la MGGL de la crème laitière. Une analyse détaillée a révélé que cette procédure est très bien adaptée pour lélimination dun maximum de protéines du lait écrémé. Une approche protéomique a été établie et a permis lidentification de protéines majeures de la MFGM ainsi que dautres protéines mineures (GTP-binding proteins, annexins, actin) afin de compléter le protéome. Par la suite, différentes protéases ont été testées en vue dobtenir différents degrés et/ou sélectivité dhydrolyse des protéines de la MGGL. La distribution asymétrique des protéines de la MGGL a été étudiée par une approche basée sur lattaque protéolytique du globule gras natif. Sur base de nos résultats et des données bibliographiques récentes, un nouveau modèle de la structure de la MGGL est proposé. La deuxième partie de cette thèse est consacrée à évaluer les propriétés technofonctionnelles de la MGGL dans les babeurres. Les propriétés interfaciales, moussantes et émulsifiantes du babeurre sont comparées à dautres ingrédients laitiers comme le lait écrémé et le concentré protéique de lactosérum. Nos résultats montrent le bon pouvoir émulsifiant du babeurre en comparaison des autres ingrédients laitiers. Dans les émulsions recombinées, la stabilité envers le crémage a été améliorée et les membranes ont présenté une meilleure résistance face à la coalescence. Les résultats sur la tension interfaciale et les propriétés rhéologiques interfaciales ont été mis en relation avec certaines propriétés des mousses et des émulsions. Vanderghem Caroline. (2009). The milk fat globule membrane: physico-chemical studies and its techno-functional valorisation in buttermilk (Thèse de doctorat). Gembloux, Belgium, Gembloux Agricultural University, 198p., 14 tabl., 59 fig. Summary The milk fat globule membrane (MFGM) is a complex structure that surrounds, protects and delivers bioactive compounds and nutrients in an efficient manner to the neonate. Its structure is unique in relation with any other biological lipid transport system. The overall aim of this work was to contribute to increase the knowledge and comprehension of this natural emulsifier. The first part of this thesis concerned the study of the structure of the MFGM. Membrane proteins were targeted and their importance regarding stability and disposition in the MFGM was studied. MFGM proteins are present at low concentrations in milk and a pre-fractionation of the sample is required in order of MFGM proteins to be visible among other milk proteins (caseins and whey proteins). A mild procedure developed in our laboratory was tested in order to isolate MFGM from cream. Detailed analysis revealed that this procedure is very well suited for the elimination of a maximum of skim milk proteins. A proteomic approach was established and allowed the identification of the most important MFGM proteins and additional minor MFGM proteins for additional completion of the proteome (GTP-binding proteins, annexins, actin). Subsequently, different proteases were screened in an attempt to obtain different degrees and/or selective proteolysis of MFGM proteins. Asymmetric arrangement of MFGM proteins was studied with an approach based on the proteolytic attack on the native fat globule. Based on our results and recent bibliographic data, an updated model of the MFGM structure was proposed. The second part of this thesis was devoted to assess the techno-functional properties of the MFGM in buttermilks. Interfacial, foaming and emulsifying properties of buttermilk were assessed and compared to classic milk ingredients such as skim milk and whey protein concentrate. Our results highlighted that buttermilk possesses good emulsifying power compared to other milk ingredients. In buttermilk recombined emulsions stability towards creaming was improved and the recombined membrane presented a great resistance to coalescence. Results of the interfacial pressure and the interfacial rheological properties were related to some foams and emulsions properties.

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