Homogenization process

Homogenization is a mechanical process that turns an unstable emulsion into a stable one. It reduces the particle size of the dispersed phase until it is uniformly distributed throughout the continuous phase. This process is commonly used in the initial steps of milk processing, and it is carried out by special pieces of equipment called homogenizers.

The standard procedure involves two steps in the so-called 2-step homogenization (Figure 1, A). Homogenization uses high pressure to reduce the particle size of the dispersed phase. To achieve this, emulsions pass through tiny orifices, which are determined by valves (Figure 1, B). As a result, there is not only a drastic decrease in the particles size but also an increase in their surface area.

Figure 1. Two-step homogenization process. A. Liquid flow in a two-step homogenization process. B. Detail of particle size when liquid passes through a valve.

During homogenization, fat globules have different size and distribution depending on the step (Figure 2).

Figure 2. Milk fat globules size and distribution according to the homogenization step. Unhomogenized milk has bigger fat globules, while after homogenization their size is decreased, being the only difference between both steps their distribution. The observed clustering is also known as flocculation.