Simply mixing together the ingredients and freezing them does not make good quality ice cream, because this does not produce the micro-structure of small ice crystals, air bubbles and fat droplets held together by the matrix. The factory process for making this microstructure is based on the same principles as the Victorians used, but it has evolved over many years to enable the rapid and cost-effective production of ice cream on an industrial scale. The details of the process vary from factory to factory, according to the type of equipment and scale of manufacture, but the basic stages, which are described in this chapter, are common to all. These are: mix preparation (which consists of dosing and mixing of the ingredients, homogenization and pasteurization), ageing, freezing and hardening. The process is summarized in Figure 4.1, which also shows the points of addition of the ingredients, including air, and the temperature changes that take place. The assembly and packaging of products by combining ice cream with other components, such as cones, chocolate, fruit, sticks, tubs etc. takes place before and/or during the hardening stage, and is covered in Chapter 5.

Figure 4.1: Schematic diagram of the manufacturing process, showing the points of addition of ingredients and components and the temperature profile