How does rendering separate fat from animal tissues?

Rendering is a primary method used to extract fats from animal tissues by liberating the fat from its cellular structure. The process can be performed through conventional or modern centrifugal techniques.12

Conventional Rendering

In conventional rendering, fatty tissue is chopped into small pieces and heated, either by boiling in open vats or cooking in steam digesters. As the heat ruptures the cells, the fat is released and floats to the surface of the water, where it is collected by skimming. The remaining solid membranous matter, known as greaves, is then pressed using hydraulic or screw presses to recover additional fat.1

Centrifugal Rendering

Developed in the 1960s, centrifugal processes offer higher yields and better quality. This method involves:
* Disintegration: Fatty tissues are ruptured in specialized equipment under strictly controlled temperatures.1
* Separation: A desludging centrifuge removes the protein tissue from the liquid phase. A second centrifuge then separates the pure fat from the remaining aqueous protein layer.1

The resulting protein residue from these processes is often utilized for animal feed or fertilizer.1