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
