Notes

Milk fat gives ice cream its distinctive richness and characteristic smooth texture. by volume, 20 to 50% of ice cream is air whipped into the mix during the early stages of the freezing process. ice cream has a colloidal structure. Tiny air bubbles and ice crystals are dispersed among liquid water and a network of destabilized fat globules. The structure contributes to the taste. the milk fat exists as tiny globules in the milky starting mixture. Milk proteins on the globules' surface work as an emulsifier to keep the fat in solution. To make the ice-cream structure, these fats need to be destabilized so that they coalesce into larger networks. "When two partially crystallized fat globules come together, like in ice cream, they form a partially coalesced structure." Egg yolks were originally used as this destabilizing emulsifier, but now, ice-cream manufacturers use mono- and diglycerides as well as the sorbitan ester Polysorbate 80.Whipping the mixture introduces air bubbles and also helps the fat globules to coalesce. These fat globules, in turn, help stabilize the air bubbles. This freezing-point depression is a colligative property arising from the sugars and salts in the ice-cream solution. As crystals of pure ice form, the solution's sugar and salt concentration increases, depressing the freezing point further. Goff says that, even at the typical ice-cream serving temperature of –16 °C, only about 72% of the water is frozen. The unfrozen concentrated solution component keeps the ice cream "scoopable" and also keeps ice-cream eaters from breaking their teeth when they bite into the treat. The size of the ice crystal is critical to the ice cream's quality. ice crystals should be small. Large crystals lead to a coarse, grainy texture. Crystal size depends on how quickly the ice cream is frozen. Slow freezing gives a small number of large crystals, whereas fast freezing promotes a larger number of nucleation sites and, consequently, a large number of small crystals. If the temperature increases during shipping, storage at the grocery store, or even as the ice cream is transported to a consumer's freezer, those tiny crystals can melt and recrystallize into larger structures. To curtail this problem, manufacturers add stabilizers such as plant-derived guar gum and carageenan. The stabilizers also prevent the air bubbles from collapsing and promote good flavor release. ice cream is a complex mix of fatty and watery components. the more you understand about chemistry, the better you can do product development." For example, Hartel says, if a company were developing a low-fat ice cream, they could not rely on the fat-soluble flavorings they use for their full-fat products. Instead, they would aim to use more hydrophilic flavorings.