First why, then how.

In a milk gelato, water makes up roughly 58–60% of the mix. When it freezes, part of it turns into ice crystals and the rest stays liquid, together with dissolved sugars and salts. That ratio of ice to liquid phase is what makes a gelato scoop easily or turn rock-hard in the display case.

That is why we don’t talk about “how much water”, but about total solids: everything that isn’t water. The more solids, the less free water is left to form large crystals. For modern milk gelato we work with at least 41% total solids.

Every sugar does two things: it sweetens (POD) and it lowers the freezing point (PAC). The catch is that they don’t all do both in the same proportion. Dextrose, for example, is about 70% as sweet as sucrose, but lowers the freezing point almost twice as much.

This means that by combining sugars you can set, separately, how sweet the gelato is and how soft it is at your display temperature. Sucrose alone rarely gets you there: the gelato ends up either too sweet or too hard.

Fat gives gelato body and a creamy feel, and it carries flavour. In milk gelato we usually work between 6% and 10%. During batch freezing, some fat globules join together and form a network that holds air and gives structure.

More is not better. Beyond a point the gelato becomes heavy, leaves a greasy mouthfeel and masks flavour, especially with fruit and chocolate. The right amount depends on the flavour, not on a fixed base recipe.

NFMS are the proteins, lactose and minerals of milk. Proteins bind water, help incorporate air and stabilise the structure. That is why a gelato with too little NFMS feels “empty” and melts quickly.

Lactose sets the limit. If NFMS rise too high relative to the water in the mix, lactose crystallises and the gelato turns sandy. In practice, milk gelato sits around 9–11%, depending on the other solids.