Structure Of Fat Globules Research Articles

Nature's complex emulsion: The fat globules of milk

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.

The overall and fat composition of milk of various species

Milk, an essential source of offspring nourishment, varies in it’s composition and properties significantly across species. In human nutrition, fresh milk and dairy products are valuable sources of protein, fat and energy, and are an important part of daily meals. Most of the world’s milk production (85 %) comes from cows followed by buffaloes, goats, ewes, mares and donkeys. However milk related food allergies in infants may be a reason for health problems and may cause a decrease in milk. The objective of this paper was to give an overview of the overall composition of milk and fat from different species in comparison to women milk. Regarding the overall milk composition remarkable differences in energy content, fat, lactose, protein and ash of the various milks were found, but also some similarities among milk from ruminants and non-ruminants were detected. The structures of fat globule membranes were similar among non-ruminants and women milk, while the milk fat globule structure in ruminants differed significantly. The size of fat globules was significantly different between species and highly correlated to the milk fat content, regardless of the specie. The amount of triacylglycerols was notably higher, while the amount of free fatty acids and phospholipids was notably lower in milk from ruminants and women compared to milk from mares and donkeys. The triacylglycerol structure in women and non-ruminantsˈ was similar. The percentage of saturated and monounsaturated fatty acids was lower, while the unsaturated fatty acid content was higher in milk from non-ruminants, with a remarkably higher percentage of C-18:2 and C-18:3. The cholesterol content was similar in women and ruminantsˈ milk, but lower in that of non-ruminants. This review indicates that milk from non-ruminants could be more suitable for human nourishment than milk from ruminants.

A novel infant milk formula concept: Mimicking the human milk fat globule structure

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.

Classification and Processing Optimization of Barley Milk Production Using NIR Spectroscopy, Particle Size, and Total Dissolved Solids Analysis

Barley is a grain whose consumption has a significant nutritional benefit for human health as a very good source of dietary fibre, minerals, vitamins, and phenolic and phytic acids. Nowadays, it is more and more often used in the production of plant milk, which is used to replace cow milk in the diet by an increasing number of consumers. The aim of the study was to classify barley milk and determine the optimal processing conditions in barley milk production based on NIR spectra, particle size, and total dissolved solids analysis. Standard recipe for barley milk was used without added additives. Barley grain was ground and mixed in a blender for 15, 30, 45, and 60 seconds. The samples were filtered and particle size of the grains was determined by laser diffraction particle sizing. The plant milk was also analysed using near infrared spectroscopy (NIRS), in the range from 904 to 1699 nm. Furthermore, conductivity of each sample was determined and microphotographs were taken in order to identify the structure of fat globules and particles in the barley milk. NIR spectra, particle size distribution, and conductivity results all point to 45 seconds as the optimal blending time, since further blending results in the saturation of the samples.

Comparative fat digestibility of goat, camel, cow and buffalo milk

The differences in the milk fat digestion from milk of different species using an in vitro digestion model were investigated. Milk samples were collected from healthy lactating goats, camels, cows and buffalos. The in vitro digestion of milk fat was carried out at pH 7.5 to mimic pancreatic lipase activity in the small intestine leading to fatty acid release from fat globules. It was found that the amount of free fatty acids released per unit volume of the milk sample decreased in the following order: goat camel > cow > buffalo. The differences in the structure of fat globules during the digestion were characterised using confocal laser scanning microscopy. The information generated provided important insights into the factors that influence the activity of lipases during lipid digestion and improve understanding of in vivo fat digestion by pancreatic lipase.

Laits maternels et formules lactées 1er âge : péroxydation lipidique

Human milk is rich in polyunsaturated fatty acids (PUFA) that are prone to oxidation. We have measured a global (MDA) and specific end-markers of n–6 and n–3 PUFA oxidation, respectively: 4-HNE and 4-HHE, from 7 breast milk samples. Analyses were performed on milk fresh or stored 1 day at 18°C or 7 days at 4°C. Ten infant formulas, liquids or in powder, some supplemented in long chain PUFA, were also studied. The ratio [4-HHE/n–3 PUFA] was 20-fold higher in liquid infant formula than in human milk (0.19 ±0.01μg.g−1). The ratio [4-HNE/n–6 PUFA] was 300-fold higher in liquid infant formula than in human milk (0.004 ±0.000μg.g−1). Storage of human milk did not increase significantly lipid peroxidation, on the contrary to infant formula where MDA increased. The native structure of fat globules in breast milk can take part in its greater protection against oxidation compared to the artificial fat droplets in infant formulas. The health consequences of chronic infant exposure to low dietary doses of lipid peroxidation products should be investigated and infant formulas should be stored in appropriate conditions.

Microstructure of Fat Globules in Whole Milk after Thermosonication Treatment

The structure of fat globules in whole milk was studied after heat and thermosonication treatments to observe what happens during these processes at the microscopic level using scanning electron microscopy. Raw whole milk was thermosonicated in an ultrasonic processor-Hielscher UP400S (400 W, 24 kHz, 120 microm amplitude), using a 22-mm probe at 63 degrees C for 30 min. Heat treatment involved heating the milk at 63 degrees C for 30 min. Color and fat content were measured to correlate the images with analytical measurements. The results showed that the surface of the fat globule was completely roughened after thermosonication. Ultrasound waves were responsible for disintegrating the milk fat globule membrane (MFGM) by releasing the triacylglycerols. Furthermore, the overall structure of milk after sonication showed smaller fat globules (smaller than 1 microm) and a granular surface. This was due to the interaction between the disrupted MFGM and some casein micelles. Minor changes in the aspect of the globules between thermal and raw milks were detected. Color measurements showed higher L* values for sonicated samples. Sonicated milk was whiter (92.37 +/- 0.20) and generally showed a better degree of luminosity and homogenization compared to thermal treated milk (88.25 +/- 0.67) and raw milk (87.82 +/- 0.18). Fat content analysis yielded a higher value after sonication (4.24%) compared to untreated raw milk (4.04%) because fat extraction is more efficient after sonication. The advantages of thermosonicated milk are that it can be pasteurized and homogenized in just 1 step, it can be produced with important cost savings, and it has better characteristics, making thermosonication a potential processing method for milk and most other dairy products.

Free Oil and Rheology of Cheddar Cheese Containing Fat Globules Stabilized with Different Proteins

Cheddar cheese was manufactured from recombined milk containing fat globules coated with αs1-CN (casein), αs2-CN, β-CN, κ-CN, α-lactalbumin, or β-lactoglobulin. The effect of the coating on fat globule structure, free oil formation, and cheese rheology was investigated to determine if globule coating affected the physical structure of cheese. Fat globule size and shape were determined in cheese using confocal laser scanning microscopy, and the rheological properties measured by uniaxial compression after maturation for 35 and 70 d. Fat globules were elongated and clustered in the control cheese coated with native membrane material and in cheese where the globules were coated with αs2-CN, but were more circular and distinct than all others. Cheese containing globules coated with αs2-CN fractured at a lower strain and with a lower stress than other experimental cheeses. Free oil decreased in cheese as the stress at fracture of the cheese protein matrix increased. Strain at fracture increased as pH increased from 4.7 to 5.3. There was no correlation between free oil and fat globule circularity. Cheddar cheese aroma was not evident in experimental cheeses.

Release of remnant plasma membrane from milk fat globules by Triton X-100

The nonionic detergent, Triton X-100, was investigated as an agent for releasing plasma membrane from milk fat globules. The sedimentable material ( 50 000 × g, 1 h) derived by treating washed goat globules with the detergent (0.2%) was compared to membrane made by the classical globule churning procedure. Characterization included lipid and protein analyses, gel electrophoresis of peptide components, determination of enzymatic activities, and examination with the electron microscope. The results established that the detergent-released material is membrane with similarities to the product by churning. Evaluation of variables revealed that a detergent concentration of 0.1 to 0.2% and reaction temperature of 20–22°C appear optimum with respect to membrane yield when a reaction time of 2 min is employed. At higher detergent concentrations or temperatures removal of phospholipid from the membrane was maximized. Triton X-100 was observed to release membrane from milk fat globules of the goat, human and cow, the latter with a minor procedural modification. The detergent based method is a convenient procedure for obtaining plasma membrane material in good yield for biochemical studies. It also should aid investigations of milk fat globule structure.