What are the emulsifiers in dairy milk?

October 13, 2025 •

3 min read

Milk is a natural oil-in-water emulsion, with tiny fat globules suspended in a water-based liquid. This delicate suspension is made possible by naturally occurring emulsifiers that prevent the fat from separating and rising to the top as a cream layer, a phenomenon known as creaming.

Quick Summary

Dairy milk contains natural emulsifiers like casein proteins and phospholipids that keep fat and water from separating. Processing methods such as homogenization and pasteurization alter these compounds, and additional emulsifiers may be added to processed milk for stability.

Key Points

Natural emulsifiers: Casein proteins and phospholipids within the Milk Fat Globule Membrane (MFGM) are the primary natural emulsifiers in raw milk.
Homogenization's effect: Processing like homogenization breaks up fat globules and replaces the original MFGM with a new stabilizing layer composed mainly of milk proteins.
Added emulsifiers: Certain processed dairy products like chocolate milk, ice cream, and fortified versions may have additional emulsifiers added for enhanced stability.
Common additives: Examples of commercial emulsifiers include mono- and diglycerides, lecithin, and carrageenan, which serve different purposes in dairy production.
Stability is key: Emulsifiers are crucial for preventing milk fat from separating and ensuring a consistently smooth texture, a process particularly important in homogenized and processed dairy products.

Understanding Emulsions in Dairy Milk

An emulsion is a stable mixture of two or more liquids that are normally immiscible, such as oil and water. Milk is an oil-in-water emulsion, where tiny droplets of fat are dispersed throughout the water-based liquid. Emulsifiers, also known as surface-active agents or surfactants, have both a water-loving (hydrophilic) end and a fat-loving (lipophilic) end. They work by coating the fat droplets, creating a protective layer that prevents them from clumping together and stabilizing the overall emulsion.

Natural Emulsifiers in Raw Milk

Raw milk contains a sophisticated system of natural emulsifiers that work together to maintain its stability. These include specialized proteins and phospholipids.

Casein Proteins

Casein is a family of phosphoproteins that makes up about 80% of the protein in cow's milk. Casein proteins exist as large, spherical clusters called casein micelles, which are amphiphilic, with both hydrophobic and hydrophilic regions. This allows them to adsorb to the surface of milk fat globules, creating a protective barrier that provides electrostatic repulsion and keeps the droplets dispersed, preventing aggregation.

The Milk Fat Globule Membrane (MFGM)

The MFGM is a complex, three-layered membrane rich in phospholipids and proteins that surrounds and stabilizes the milk fat droplets in raw milk. Phospholipids, a fundamental component of the MFGM, have strong emulsifying properties due to their amphiphilic structure. The MFGM is the primary stabilizing agent for fat globules in raw, unprocessed milk and also contains bioactive compounds with potential nutritional benefits.

The Effect of Processing on Milk's Emulsion

Modern milk processing, including pasteurization and homogenization, significantly impacts the natural emulsification system of milk.

Homogenization

Homogenization is a physical process that breaks down large fat globules into smaller, more uniform ones by forcing milk through a small valve at high pressure. This process disrupts the original MFGM. As the smaller fat globules increase the total surface area, they are covered by a new membrane formed primarily from casein micelles and whey proteins present in the milk. This results in a more stable emulsion, preventing creaming.

Pasteurization

Pasteurization involves heating milk to kill harmful bacteria. While heat can cause some protein denaturation and aggregation, in homogenized milk, the effect on emulsion stability is generally managed, especially when additional emulsifiers or stabilizers are used in certain products.

Added Emulsifiers in Commercial Dairy Products

Many processed dairy products, such as ice cream, chocolate milk, and concentrated milks, contain additional emulsifiers to improve texture, stability, and shelf life.

Common Added Emulsifiers

Mono- and Diglycerides (E471): Used in ice cream and other products to prevent fat separation and enhance texture.
Lecithin: Often from soy or egg yolks, used to stabilize emulsions and prevent crystallization in cheese.
Carrageenan (E407): Extracted from red seaweed, acts as a thickener and stabilizer, often added to chocolate milk to prevent settling.
Polysorbate 80: A synthetic emulsifier used in products like whipped cream and ice cream for improved consistency.

Comparing Natural and Added Emulsifiers


Feature	Natural Emulsifiers	Added Emulsifiers
Composition	Casein proteins and phospholipids within the Milk Fat Globule Membrane (MFGM).	Mono- and diglycerides, lecithin, carrageenan, polysorbates, etc..
Role in Plain Milk	Naturally stabilizes raw milk by preventing fat globules from coalescing and separating.	Not typically added to plain, fresh milk, which is naturally stable.
Role in Processed Milk	The casein layer that forms after homogenization takes over much of the natural emulsifying function.	Added to specific products (e.g., chocolate milk, fortified milks, ice cream) for enhanced stability, texture, and shelf life.
Effect on Fat Globules	Creates a complex, native MFGM in raw milk.	Help form and reinforce the new fat globule membrane after homogenization.
Regulatory Status	Generally considered natural components of milk.	Categorized as food additives and regulated by food safety authorities.

The Function of Emulsifiers in Dairy Products

Emulsifiers are crucial for the sensory properties of dairy products. They contribute to a smooth texture and creamy mouthfeel, prevent separation for a consistent appearance, extend shelf life, and aid in integrating added ingredients like omega-3 fatty acids in fortified milks.

Conclusion

Dairy milk's emulsification system involves both natural components like casein proteins and the phospholipid-rich MFGM in raw milk, and in some processed products, added emulsifiers. Homogenization modifies the natural system by creating a new protein-based membrane around smaller fat globules. Additional emulsifiers are used in various dairy products to ensure desired texture, stability, and shelf life. This blend of natural and added emulsifiers results in the consistent quality of the dairy products we consume(https://researchportal.hw.ac.uk/en/publications/emulsifiers-in-dairy-products-and-dairy-substitutes-4).

Frequently Asked Questions

No. Plain, fresh milk is naturally stabilized by its proteins and fats. Additional emulsifiers are only typically added to processed products like flavored milks, ice cream, or fortified versions for specific functional needs, such as improved texture or preventing separation.

The MFGM is a complex, natural membrane made of phospholipids and proteins that surrounds the fat globules in raw milk, stabilizing the emulsion. It is disrupted by homogenization.

Homogenization uses high pressure to break up large fat globules into smaller, more uniform ones. This process replaces the original MFGM with a new membrane made largely of casein and whey proteins, preventing the cream from rising.

Emulsifiers are added to flavored milks, such as chocolate milk, to prevent the added solids (like cocoa) or other ingredients from settling to the bottom. They ensure a uniform and consistent product texture.

Mono- and diglycerides are common food additives derived from fatty acids. In many dairy products, including ice cream and concentrated milks, they help stabilize the fat emulsion and prevent separation, enhancing the product's texture and shelf life.

Yes, beyond its emulsifying properties, the MFGM contains biologically active lipids and proteins. Research suggests these components may provide health benefits, especially in infant nutrition, and efforts are being made to preserve them in processed products.

Yes, most added emulsifiers used in food production are widely studied and considered safe for consumption by food safety regulatory bodies worldwide. Their use is approved to enhance food quality and stability.

The cream layer forms on raw or unhomogenized milk because the larger, less dense fat globules naturally rise and collect at the surface. This happens because the natural emulsification provided by the original MFGM is not strong enough to overcome the density difference over time.