That famously delicious mouth-feel of Italian ice cream is created by using a stabiliser.
Left to their own devices, the oils and water within ice cream won’t mix together very well. Fat molecules will be drawn to other fat molecules and water molecules to other water molecules.
A stabiliser creates a permanent bond to both the water and the fatty molecules, regimenting the ice-cream structure, reducing air-loss, the formation of ice crystals and flooding on the plate.
When you turn ice-cream, you have no control over where the molecules will end up. Anywhere that you end up with fat molecules touching other fat molecules, you will create a heavy, dense part to your ice-cream.
Part of the joy of ice-cream is the fact that you’ve got an ‘over-run’ resulting from the air within the ice-cream, giving you the smoothness and the mouth-feel. If you’ve got two fat molecules that touch, then the air can very easily escape along the slippery surface of the fat molecules. This results in molecular movement within the ice-cream; the fat molecules tend to drop, sugar molecules collect in one area and water molecules collect together. If you’ve got long-chains of water molecules together in the freezer, you get ice crystals.
If you’ve added a stabiliser, which bonds the fat and water together and has basically regimented the way the different types of molecules sit, then the air can’t escape so easily, ice crystals can’t build up in the freezer and there’s no flooding on the plate!
The stabilising elements are mono- and di-glycerides of fatty acids (vegetarian-based). These molecules have ‘spiral hooks’ on either side, each type (mono and di) has a permanent bond to either the fat or the water molecules. It’s a little like a battery with a + and -, each attracting either water or fat!