The Chemistry of Gelato. http://www.youtube.com/watch?v=4VA5vEi4tWU. The structure of gelato : Gelato is considered a colloid or suspension of air and ice crystals in a sugar solution. Air Ice crystals Fat Sugar. http://www.icecreamnation.org/science-of-ice-cream/
Gelato contains all three states of matter simultaneously
4. Ageing– the stabilizers bind to the surface of the fat droplets and the fat droplets begin to harden (crystalize). The stabilizer helps to keep the fat droplets small after they’ve been broken up, by binding to the surface of the droplets.
5. Churning and freezing– air is added to the mixture while the temperature is lowered. Gelato contains much less air (30-40%) than ice cream (50%) which contributes to its creamier texture. It is also served at a higher temperature.
The fat droplets partially crystalize and help to stabilize the air bubbles.
Ice cream scientists use the freezing point curve when formulating ice cream recipes. Suppose, for example, they want to make 1 kg of ice cream that contains 50 per cent ice by weight at a normal freezer temperature of -18°C. How much sucrose should they use? From the curve, the sucrose mole fraction in equilibrium with ice at -18°C is 0.083 or 63 per cent w/w, ie:
Msucrose/(Msucrose + Mwater) = 0.63
The total mass is 1 kg, and 50 per cent of this will be ice, so the remainder, must be sucrose and unfrozen water.
Msucrose+ Mwater = 500 g
Solving these two equations gives Msucrose = 320 g.
Freezing must be done quickly so that the ice crystals formed are as small as possible.
Ice crystals at -10°C Ice crystals warmed to -7°C Ice crystals re-cooled to -10°C