The manufacturing method
To make your ice cream, you will have to follow a method that can be divided in 6 steps.
1st step : Pasteurization
All ingredients will be mixed and undergo a pasteurization cycle to eliminate bacteria. There are several ways to make this pasteurization.
Heating the mix at 100°C destroys all germs. But it is no longer pasteurization and we should instead talk about sterilization. The disadvantage is that we will have an alteration of the flavor and color of certain ingredients. Morevoer, some ingredients (eggs for example) can not withstand such a high temperature. This technique will therefore not be used.
Low temperature pasteurization consists in keeping the mix at a 65°C temperature during 30 minutes. It will not be used for pratical reasons.
High temperature pasteurization consists to bring the mix at a 85°C temperature during a few seconds. It will be the technique we will use because it is easier to proceed so. It has also the advantage to favour the efficiency of emulsifiers/stabilizers and to obtain a better fat emulsion. Finally, with eggs in the recipe, it is safer to use high pasteurization while taking care not to exceed 85°C to avoid ending up with an omelet.
Pasteurization not destroying all the germs, it will be essential to cool the mixture as quickly as possible. Bacteria still alive will not withstand the sudden cold. It is necessary to lower the temperature to 4°C as fast as possible in one or two hours. The most critical phase is when the mix temperature is between 40°C and 20°C.
Impossible to do this at home ? Absolutely not. When the temperature reaches 85°C, pour your mix in another container and immerse it in an ice water bath then in the refrigerator.
2nd step : Homogenization
The homogenization occurs when temperature is between 75°C and 65°C during cooling time of pasteurization. It consists in breaking up the solids (mainly fat) into small particles.
This phase is rather reserved for industrial manufacture and will not be necessary for homemade ice cream. A few seconds with an hand blender after pasteurization and it will be OK.
3rd step : Ageing
The ageing consists in keeping the mix at 4°C with slow stirring for 6 to 12 hours. This essential step allows to initiate the crystallation of fat, to ensure a good texture and to exhale the flavors.
At home, ageing will simply consists in letting the mix stand one night in the fridge because it is difficult to have a system stirring the mix during this phase.
4th step : Creaming
Here is the step during which the ice cream will actually be made. It consists in cooling the mixture while incorporating air.
At home, we will use for that our ice-cream maker.
5th step : Cooling
When creaming is over, ice cream will reach a -10°C temperature. It must be cooled as fast as possible to -30°C for industrial productions.
At home, it will consist in storing the ice cream in a freezer at -18°C.
6th step : Tasting
It is now finished ! The next day, your ice cream will have hardened well so you can finally taste it.