What does ‘Creaming’ mean in dairy?

Creaming wears many hats when it comes to dairy. The term “creaming” in dairy science can refer to several related but distinct processes, depending on the context and the product. Here is a comprehensive overview of its various definitions:

1. Cream separation in milk

Classic definition: Creaming is the process by which fat globules in milk rise to the surface to form a layer of cream, due to their lower density compared to the aqueous phase. This occurs naturally in unhomogenized milk, often described by Stokes’ Law of sedimentation (or flotation, in this case).

Influencing factors: Fat globule size, temperature, time, viscosity of milk, and whether the milk has been homogenized.

2. Mechanical creaming (Centrifugation)

In dairy processing, creaming can also refer to the mechanical separation of cream from milk using a cream separator (centrifuge), which accelerates the process. Centrifugal force accelerates the separation of fat from the aqueous phase, allowing efficient collection of cream.

Influencing factors: Centrifuge speed, temperature, fat content, and milk viscosity.

3. Creaming in fermented dairy products (e.g., yoghurt, curd)

Sometimes, “creaming” is used to describe the migration and accumulation of fat at the surface of fermented products like yogurt or curd, forming a creamy top layer during fermentation and cooling. During incubation and subsequent cooling, fat migrates and coalesces at the surface, leading to a visible cream layer.

Influencing factors: Fat content, fermentation time, cooling rate, and product handling.

4. Creaming in cheese making

In cheese making, “creaming” can refer to the adjustment of the fat content of milk by adding or removing cream to make cheese milk for cheese production. While in some soft cheeses, creaming describes the formation of a creamy layer on the surface due to fat migration during ripening known as surface creaming. The mechanism for the first case is physical standardization of milk, and migration of fat within the cheese matrix during ripening/storage, resulting in a creamy surface for the second.

Influencing factors: Cheese variety, milk standardization, and ripening conditions.

5. Creaming in butter making

“Creaming” also refers to the first stage in butter making, where cream is churned to concentrate fat globules causing fat globules to cluster and concentrate before phase inversion and butter formation. Mechanical agitation disrupts the membrane of fat globules, causing them to coalesce and separate from the buttermilk.

Influencing factors: Churning speed, temperature, and fat content of the cream.

6. Creaming in dairy emulsions

In dairy emulsions (like cream liqueurs or processed cheese), creaming refers to the upward movement of fat droplets, leading to a fat-rich upper layer — a sign of emulsion instability. Fat droplets in the emulsion rise due to their lower density, and may coalesce, resulting in visible separation.

Influencing factors: Emulsifier type, droplet size, storage temperature, and viscosity of the emulsion.

7. Processed Cheese

In cheese science and processed cheese manufacture, “creaming” can describe the process by which the molten cheese mass thickens or increases in viscosity during heating. This thickening is primarily a protein-based interaction: as the cheese is heated, proteins (mainly caseins) interact and form a network, trapping water and fat, leading to a creamy, thick consistency. Starch, when added, can further influence this process by absorbing water, swelling, and interacting with the protein network, thus modifying the texture and viscosity of the melted cheese.

Influencing factors: Protein content, type and amount of emulsifying salts, presence and type of starch, heating temperature and time, and moisture level.

In summary