Cow Milk Fat Globules Research Articles

Differences in proteomic profiles and immunomodulatory activity of goat and cow milk fat globule membrane

This study aimed to clarify the composition and bioactivity differences between goat and cow milk fat globule membrane (MFGM) protein by proteomic, and the immunomodulatory activity of MFGM proteins was further evaluated by using mouse splenic lymphocytes in vitro. A total of 257 MFGM proteins showed significant differences between goat and cow milk. The upregulated and unique MFGM proteins in goat milk were significantly enriched in the positive regulation of immune response, negative regulation of Interleukin-5 (IL-5) secretion, and involved in nucleotide-binding oligomerization domain (NOD)-like receptor signaling. The contents of IL-2 and Interferon-γ in the supernatant of spleen lymphocytes treated with goat MFGM proteins were much higher than those of IL-4 and IL-5, suggesting a Th1-skewed immune response. These results revealed that goat MFGM proteins could possess better immunomodulatory effects as compared to cow milk. Our findings may provide new insights to elucidate the physiological functions and nutritional of goat milk.

Comparison of lipid structure and composition in human or cow's milk with different fat globules by homogenization.

Homogenization is used in human milk to add supplements for premature infants and in cow's milk to make it more uniform and stable for commercial purposes. However, it may destroy the milk fat globule (MFG) structure and composition, affecting its functional characteristics. This study aims to compare human and cow's milk with particle size ranges of 4-6 μm (large-sized), 1-2 μm (medium-sized), and 0.3-0.5 μm (small-sized) before and after homogenization at different pressure levels. CLSM and SDS-PAGE were used to perform the structural characterization. The lipid compositions were analyzed using GC and LC-MS. The results showed that homogenization obviously changed the MFG structure and its lipid composition. After homogenization, more caseins and whey proteins were adsorbed on both the human and cow's milk fat globule interface, while the proteins observed in human milk were dispersed. This could be attributed to the different types and contents of proteins initially. The influence of homogenization on milk phospholipids was higher than triacylglycerols and fatty acids, which was highly correlated with their initial distributions in MFGs. These results provide new information about the interfacial composition of human and cow's milk fat globules upon homogenization and establish the scientific basis for homogenization application in human and cow's milk to help explore their potential functions.

Composition and interfacial properties play key roles in different lipid digestion between goat and cow milk fat globules in vitro

The different TAG, interfacial properties and digestion rate between goat and cow milk fat globules were investigated. The mechanism of their different lipid digestion was also elucidated. Raw goat milk fat globules had smaller size, less large molecular weight and unsaturated TAG, larger liquid-ordered region and fewer glycoproteins, which contributed to the higher digestion rate than cow milk. After homogenization, the goat lipids also had higher digestion rate that was attributed to the special structure of easy-to-digest TAG and less glycosylated molecules not globule size. More integrated phospholipid layers and glycosylated molecules of HTST milk fat globules resulted in a lower lipid digestion rate than other processed milks. No difference in digestion rate between pasteurized goat and cow milk fat globules might be explained by the more denatured proteins and glycosylated molecules, respectively. Therefore, the TAG and interfacial properties contributed to different digestion between goat and cow milk fat globules.

Emulsions containing optimum cow milk fat and canola oil mixtures replicate the lipid self-assembly of human breast milk during digestion

HypothesisThe digestion of different milks and milk substitutes leads to the formation of a variety of self-assembled lipid structures, with the structuring of human milk being paramount for infant nutrition. It was hypothesised that mixing cow milk fat rich in medium/long-chain lipids with canola oil rich in long-chain unsaturated lipids would replicate the structuring of human milk by balancing lipid chain lengths and saturation levels. ExperimentsEmulsions of cow milk fat/canola oil mixtures were prepared in two ways – by pre-mixing ghee and canola oil before dispersing them and by dispersing canola oil directly into commercial cow milk. Small angle X-ray scattering combined with titration of the fatty acids produced during digestion allowed for the correlation of dynamic lipid self-assembly with the extent of lipid digestion. Laser light scattering was used to show that the particle sizes in the digesting mixtures were similar and coherent anti-Stokes Raman spectroscopy (CARS) microscopy was used to confirm the mixing of canola oil into cow milk fat globules. FindingsAs the amount of long-chain unsaturated canola oil lipids in the mixtures increased, the lipid self-assembly tended towards colloidal structures of greater interfacial curvature. When the ratio of cow milk fat to canola oil lipids was 1:1 (w/w), the digesting lipids assembled themselves into the same liquid crystalline structures as human breast milk. This observation was independent of the method used to mix the lipids, with CARS microscopy indicating uniform mixing of the canola oil into cow milk upon ultrasonication.

Identification and Characterization of whey Protein, Casein Micelles and Fat Globules in Cow Milk

Pasteurized cow milk (whole milk) was used in the present study and also fat was removed from the whole milk to obtain skimmed milk. Whey is the liquid remaining after milk has been curded and strained during the manufacture of cheese. The sample was filtered using a Whatman filter paper to separate the precipitate. The filtrate thus obtained is called whey (devoid of casein and fat). The micrographs of whole milk, skimmed milk and whey were obtained using an inverted phase contrast microscopy. The hydrodynamic size and zeta potential of the samples were obtained using Dynamic light scattering technique. Atomic force microscopy was also performed to understand the surface morphology of whole milk, skimmed milk and whey on mica substrate.

Shifts in the Holstein dairy cow milk fat globule membrane proteome that occur during the first week of lactation are affected by parity

BackgroundThe milk fat globule membrane (MFGM) proteomes of colostrum and transition milk are rich sources of proteins that are likely important for neonatal calf health. In addition, characterization of these proteomes could also yield valuable information regarding mammary gland physiology of the early postpartum lactating cow. The objectives of this research were to characterize the MFGM proteomes of colostrum and transition milk through sample collections at four timepoints postpartum, including the first milking (M1, colostrum), second milking (M2, transition milk), fourth milking (M4, transition milk), and fourteenth milking (M14, mature milk), and compare these proteomes between multiparous (MP; n = 10) and primiparous (PP; n = 10) Holstein dairy cows. Isolated MFGM proteins were labeled using Tandem Mass tagging and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Protein identification was completed using MASCOT and Sequest in Proteome Discoverer 2.2. The scaled abundance values were analyzed using PROC MIXED in SAS to determine the effects of milking (MIL), parity (PAR), and MIL × PAR. The adaptive false-discovery rate (FDR)-adjusted P values were determined using PROC MULTTEST. Protein characterization and bioinformatic analysis were completed using a combination of PANTHER, Blast, and Uniprot.ResultsA total of 104 common proteins were identified in each of the MFGM samples. Statistical analysis revealed that 70.2% of identified proteins were affected by MIL. Of these, 78.1% were lower in M14 compared with M1, including immune-related proteins lactotransferrin, lactadherin and hemopexin. Parity affected 44.2% of proteins. Of the proteins affected by PAR, 84.8% were higher in MP cows compared with PP cows, including apolipoprotein E and histones 2A, 2B, 3, and 4 b. Butyrophilin subfamily 1 member 1A and annexin 5 were higher in samples from PP cows. Milking × parity affected 32.7% of identified proteins, including lactotransferrin, gelsolin, vitamin D binding protein, and S100 proteins.ConclusionsThis research supports previous findings that the Holstein MFGM proteome changes rapidly during the first week of lactation. In addition, this research identifies the impact of parity on the colostrum and transition milk MFGM proteomes, which may be important for milk-fed calf health or for the identification of protein biomarkers for mammary functionality.

Simulated in vitro infant gastrointestinal digestion of yak milk fat globules: A comparison with cow milk fat globules

Lipolysis products released during digestion exert positive metabolic impacts on the nutrition of newborns. However, the lipolysis behavior of yak milk lipids during digestion remains unknown. In this study, the simulated in vitro infant gastrointestinal digestion of cow, yak and standardized yak milk fat globules the same size as those from cow milk (Cow MF, Yak MF and Yak SMF) were compared. Although Cow MF showed a higher lipolysis rate at the beginning of gastric digestion, Yak MF and Yak SMF exhibited a higher lipolysis level during later gastrointestinal digestion. Higher hydrolysis efficiency of yak milk lipids was due to their lipid properties, including their composition and structure. Furthermore, yak milk lipids released more unsaturated fatty acids than Cow MF throughout digestion. This study highlights the crucial role of lipid characteristics in the efficient digestion of milk lipids and provides new insight for the design of yak milk infant diets.

Oil bodies from dry maize germ as an effective replacer of cow milk fat globules in yogurt-like product formulation

The effect of the maize germ oil bodies in the form of a highly stable emulsion as a substitute for cow milk fat globules was investigated on the textural, physicochemical and sensory properties of a yoghurt-like product using a commercial yoghurt culture. The natural emulsion gave a satisfactory acidification kinetics pattern and an acid gel with a liquid-like structure. Gel formation was enhanced by skim milk incorporation, even more effectively when compared with cow milk with equal total solid content (16%, w/v), as determined by acidity, water holding capacity, syneresis, rheological and texture profile analysis. Studies on microbiological, physical and oxidative stability of the fortified yoghurt-like product reflect its quality assurance upon refrigerated storage. Different classes of endogenous bioactive constituents (mono- and polyunsaturated fatty acids, tocopherols) and volatile compounds derived from maize germ contribute to its high quality.

Evaluation of six sample preparation procedures for qualitative and quantitative proteomics analysis of milk fat globule membrane.

Proteomic analysis of membrane proteins is challenged by the proteins solubility and detergent incompatibility with MS analysis. No single perfect protocol can be used to comprehensively characterize the proteome of membrane fraction. Here, we used cow milk fat globule membrane (MFGM) proteome analysis to assess six sample preparation procedures including one in-gel and five in-solution digestion approaches prior to LC-MS/MS analysis. The largest number of MFGM proteins were identified by suspension trapping (S-Trap) and filter-aided sample preparation (FASP) methods, followed by acetone precipitation without clean-up of tryptic peptides method. Protein identifications with highest average coverage was achieved by Chloroform/MeOH, in-gel and S-Trap methods. Most distinct proteins were identified by FASP method, followed by S-Trap. Analyses by Venn diagram, principal-component analysis, hierarchical clustering and the abundance ranking of quantitative proteins highlight differences in the MFGM fraction by the all sample preparation procedures. These results reveal the biased proteins/peptides loss occurred in each protocol. In this study, we found several novel proteins that were not observed previously by in-depth proteomics characterization of MFGM fraction in milk. Thus, a combination of multiple procedures with orthologous properties of sample preparation was demonstrated to improve the protein sequence coverage and expression level accuracy of membrane samples.

Microstructural and lipid composition changes in milk fat globules during milk powder manufacture

The purpose of this study was to investigate the effects of milk powder processing conditions (pasteurisation, homogenisation and spray-drying) on the microstructure and composition of fat globules in cow milk.

The size and interfacial composition of milk fat globules are key factors controlling triglycerides bioavailability in simulated human gastro-duodenal digestion

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 μm, large LFG 6.6 μm, small SFG 1.7 μm) or homogenised±heat-treated (0.3 μm) 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.

Buffalo vs. cow milk fat globules: Size distribution, zeta-potential, compositions in total fatty acids and in polar lipids from the milk fat globule membrane

Although buffalo milk is the second most produced milk in the world, and of primary nutritional importance in various parts of the world, few studies have focused on the physicochemical properties of buffalo milk fat globules. This study is a comparative analysis of buffalo and cow milk fat globules. The larger size of buffalo fat globules, 5 vs. 3.5 μm, was related to the higher amount of fat in the buffalo milks: 73.4 ± 9.9 vs. 41.3 ± 3.7 g/kg for cow milk. Buffalo milks contained significantly lower amount of polar lipids expressed per gram of lipids (0.26% vs. 0.36%), but significantly higher amount of polar lipids per litre of milk (+26%). Buffalo and cow milk fat globule membranes contain the same classes of polar lipids; phosphatidylethanolamine, sphingomyelin (SM) and phosphatidylcholine (PC) being the main constituents. A significant higher percentage of PC and lower percentage of SM were found for buffalo milks. The fatty acid analysis revealed that saturated fatty acids, mainly palmitic acid, trans fatty acids, linolenic acid (ω3) and conjugated linolenic acid were higher in buffalo milk than in cow milk. Such results will contribute to the improvement of the quality of buffalo milk-based dairy products.

Solubilization methods and reference 2-DE map of cow milk fat globules

Milk fat globules (MFGs) are secretory vesicles assembled and secreted by mammary epithelial cells during lactation. They consist of fat globules surrounded by a lipid bilayer membrane which is derived from the apical membrane of the lactating cells. MFGs contain, besides lipids, proteins from the apical plasma membrane and from the cytoplasmatic material. Their peculiar vesicle nature makes them a suitable and easily available source of biological material in monitoring the physiopathological state of the mammary gland. Unfortunately, the conspicuous lipidic component of MFGs consistently limits protein extraction and purification for MFG proteomic investigations. This work deals with the development of a suitable procedure for protein extraction from the cow MFGs in order to qualitatively and quantitatively improve 2-D electropherograms of the MFG. MFGs were purified from raw milk by centrifugation and then delipidated/precipitated. The resulting protein pellets were solubilised using four different 2-D SDS PAGE compatible lysis buffers. Applied methodological procedures for protein extraction and evaluation of the resulting 2-D protein-pattern are presented and discussed. Using these procedures a reference 2-D map of cow milk fat globules is also reported. The majority of the obtained identifications was represented by proteins involved in lipid synthesis or in fat globule secretion.

Contribution to the study of camel milk fat globule membrane

The camel milk fat globule membrane has been characterized according to several approaches. Compared with the cow milk fat globule membrane, various specificities have been revealed. Its physicochemical composition showed a poor content in proteins, and a higher content in neutral lipids and in phospholipids. The mechanical properties measured at low (4°C, 20°C) and high temperatures (40°C, 45°C and 50°C) using a film balance are different when the camel milk fat globule membrane is spread at the air–water interface. The thermal study revealed an important proportion of high-melting triacylglycerols that involves fatty acids with long chains.

Quantitative characterization of phospholipids in milk fat via 31P NMR using a monophasic solvent mixture.

The phospholipids (PL) occurring in both ewe and cow milk fat globule membrane were identified and quantitatively determined using 31P NMR spectroscopy with inverse gated decoupled sequences, which allowed a rigorous quantitative analysis. A strict relation between amount and distribution of PL and type of feeding was found. The method was calibrated over a mixture of PL standards. A recently introduced solvent constituted by a monophasic dimethylformamide/triethylamine/guanidinium hydrochloride solvent mixture was used. Compared to the traditional chloroform/methanol/water-EDTA solvent, the new solvent mixture shows very similar accuracy and precision from a quantitative point of view. The monophasic solvent overcomes the partition problems related to a biphasic system, and slightly enlarges the range of 31P NMR chemical shifts, thus improving the resolution. In addition, the new solvent apparently displays a lower chemical shift dependence on the various PL concentrations. The limit of the method is mainly determined by the formation of adducts between triethylamine and some PL, namely, PE, monomethylphosphatidylethanolamine, phosphatidylethanolamine plasmalogens, and some lyso-PL. However, the new 31P NMR signals arising from these adducts could be easily quantified in the determination of PE.

ＭＦＧＭ（牛乳脂肪球被膜）の乳化能とその油脂エマルション安定性に及ぼす油脂成分の影響

A cow milk fat globule membrane (MFGM) has an excellent emulsifying ability against lipids. In this study we examined the effect of oil phase on emulsifying ability of MFGM and on stability of its emulsion and comparison with other surface active substances. In addition to that there was no significant differences of diameter of MFGM emulsions among those with various oils : triolein, ethyl eicosapentanoate, butter oil and soybean oil, they also did not greatly affect the stability of those emulsions which was determined by their turbidity. Although MFGM exerted less solubilizing ability against lipid soluble drug, its emulsifying ability was almost equal as sucrose fatty acid esters having good emulsifying ability and no toxicity. In relation of the emulsifying ability of MFGM to other substances in milk : casein (isoelectric pH 4.7), a major protein in milk but not included in MFGM, showed pH dependent its emulsion stability as well as MFGM, that is stable in weak alkaline and unstable in weak acidic solution. It was reported that the mean isoelectric point of whole MFGM is close to pH 5. These facts suggest the possibility that proteins in MFGM might contribute to its emulsifying ability.