Understanding Milk Fat Globules: Structure, Function, and Nutritional Benefits

Milk fat globules (MFGs) are integral components of milk, originating in the mammary epithelial cells. As they move toward the apical cell membrane, they grow in size before being extruded into the alveolar lumen. The diameter of these globules ranges from 0.1 μm to 15 μm, with a volumetric average of around 4 μm. This variation is influenced by factors such as cow breed, feed, and season.

Structurally, MFGs are composed of a triglyceride-rich core surrounded by a tri-layer membrane known as the milk fat globule membrane (MFGM), which is derived from mammary gland epithelia. The core of MFGs contains a wide range of fatty acids, while the MFGM, which stabilizes the globule, is a complex mixture of 60% protein and 40% fat. This membrane, approximately 10-20 nm thick, acts as an emulsifier, protecting the globules from coalescence and enzymatic degradation.

The MFGM is primarily made up of phospholipids, glycolipids, proteins (which account for 25-60% of its mass), lipoproteins, and enzymes such as butyrophilin and xanthine oxidase. This highly structured membrane contains unique polar lipids and membrane-specific proteins. Sphingolipids, which are highly bioactive molecules predominantly found in animal-derived polar lipids, constitute up to one-third of the MFGM polar lipid fraction. These components play a crucial role in protecting fat globules from lipolysis catalyzed by lipase activity, which is mainly linked to the casein micelles.

The size and distribution of fat globules significantly affect the viscosity of milk and have implications for the processing and manufacture of milk products. Smaller fat globules tend to be better dispersed, resulting in a more homogeneous mixture of fat in milk. Their small size leads to a higher phospholipid content due to the increased surface area. This characteristic is beneficial in dairy product formulations, providing desirable textural and stability properties.

Recent research highlights the importance of MFGM in the development of brain and nerve tissues, as well as its role in the absorption and digestion of fat. This has led to an increased interest in the nutritional and functional applications of MFGM components. Due to their origin, composition, and structure, MFGM polar lipids and proteins have potential uses as emulsifiers or stabilizers, combining technological functionality with nutritional benefits.

One of the main factors responsible for the rapid formation of a cream layer on cow milk is a heat-denaturable protein adsorbed on cold fat globules, which exhibits characteristics of a euglobulin. This protein, known as fat agglutinin, promotes the clustering of globules, facilitating the creaming process.

Overall, the intricate structure and composition of MFGs and MFGM not only contribute to the physical properties and stability of milk but also offer significant health benefits. Continued research in this area promises to enhance our understanding and utilization of these components in both dairy science and nutrition.
Understanding Milk Fat Globules: Structure, Function, and Nutritional Benefits

α-Lactalbumin

α-Lactalbumin is a globular protein that constitutes approximately 22% of the proteins in human milk and approximately 3.5% of those in bovine milk

It is the second major protein of bovine whey. It has a molecular weight of 14 kDa and accounts for about 20% of the total whey proteins.

α-Lactalbumin biological actions are attributed such as stress reduction
*Antibacterial activity
*Antihypertensive action
*Regulation of cell growth, anti-ulcer activity
*Immunomodulating, but above all specific intestinal actions.

It is an important source of bioactive peptides and essential amino acids, including tryptophan, lysine, branched-chain amino acids, and sulfur-containing amino acids, all of which are crucial for infant nutrition.

Due to the high content of branched-chain amino acids ( ~26%), especially leucine, α-Lactalbumin effectively supports and stimulates muscle protein synthesis, making it the ideal protein source for improving muscle health and help prevent sarcopenia during ageing.

The protein can be isolated from milk using chromatography/gel filtration, membrane separation, enzyme hydrolysis, and precipitation/aggregation technologies.

α-Lactalbumin contributes to reducing the risk of incidence of some cancers (e.g., breast and colon cancer), as it constrains cell division when present in intestinal cell lines. α-Lactalbumin as a protein source increases blood tryptophan levels, which promotes the synthesis and availability of serotonin in the brain. In turn, serotonin supports the production of melatonin, the hormone that helps regulate sleep patterns.
α-Lactalbumin