By this stage of the processing, the mix is basically an oil in water emulsion. Homogenisation reduces the size of the oil droplets to a much smaller diameter and renders the mix more stable towards separation and clumping. The homogenised mix is smoother and more uniform and generally has an improved whipping ability; the resultant ice cream has better melt-down. During this process, the milk protein and surface active agents are distributed onto the fat globule surfaces.

Homogenisation is best effected at the pasteurising temperature and consists of passing the mix through a very small opening under high velocity and high pressure. There is a tendency for the fat particles to clump as the mix passes away from the homogenising valve, particularly if the mix is cold (less than 120°F) or more acid than usual, or based on butter. If this clumping becomes marked, the mix becomes more viscous and slower to whip and freeze, and for this reason two stage homogenisation is sometimes used. In this, the mix is passed through a valve at relatively high pressure (about 2500psi) and then through a second valve at a lower pressure (about 500psi) to break up any clumps which are formed. The actual pressures used depend on a number of factors, including the composition of the mix. Mixes with higher fat content are homogenised at lower pressures. The viscosity of the mix can be reduced by lower homogenising pressures, higher temperature at homogenisation and by the use of a second valve.

All content is copyright Harbour Bar Ltd. 2013.