Introduction to making ice cream
Ice cream consists of a few simple ingredients; cream and/or milk, egg yolks, sugar and flavorings or fruit juices or purees.
Ice cream texture
The creaminess in ice cream comes from a balanced level of fat and sugar in the recipe. Emulsifiers and stabilizers are what control the mouth feel and texture of the final product. Creaminess in an ice cream comes from the even distribution of air bubbles (controlled by the stabilizer) throughout the mixture, and the size of the ice crystals (controlled by the emulsifier).
Ice creams made at home contain egg yolks which contain lecithin. Lecithin is an emulsifier, which helps maintain an even distribution of fat particles all throughout the ice cream. On the other hand, commercial versions of ice cream contain stabilizers and emulsifiers, instead of egg yolks.
Individual ingredient effects when making ice cream
If you use only cream (35%), the ice cream will have a pronounced butter taste.
Egg yolks contain lecithin (protein), which gives softness to the ice cream.
Using too much glucose in the ice cream mixture will give a rubbery texture to the ice cream.
If you use only milk (2%), the ice cream may not thicken enough. Adding a bit of milk powder in the ice cream gives texture and improves overrun.
Sugar gives a softer ice cream because it reduces the formation of ice crystals and at the same time lowers the freezing point of ice cream. Another words the ice cream needs to be frozen at a lower temperature in order to freeze. The lower the freezing temperature of the ice cream means that you have more time to churn the ice cream mixture in the ice cream machine before it freezes and this in turn gives you more time to incorporate more air into the ice cream giving you a softer end product.
Stabilizers in ice cream absorb the water contained within the ice cream mixture. This prevents formation of ice crystals after freezing the ice cream.
Emulsifiers cause the fats to be distributed very finely all throughout the ice cream mixture, enabling the creating of an emulsion between the fats and the water.
Other ingredients used in ice creams
Atomized glucose does not impart much sweetness, but it is used primarily to prevent the water (contained in the ice cream) from forming ice crystals (crystallization). If you use too much, the ice cream may get a somewhat rubbery texture.
Invert sugar also called Trimoline, is used for the same purpose as Atomized glucose, except it also imparts a lot of sweetness to the final product.
If you add cocoa powder in an ice cream recipe, you need to compensate with an addition of extra sugar.
Procedure for making ice cream
One of the procedure for making ice cream, is exactly the same as for making Créme Anglaise (English cream). You nee to heat the cream/milk mixture with half the sugar until mixture comes to a boil. Allow about to cool slightly.
While the milk/cream mixture is cooling, whisk the egg yolks with remaining sugar until light pale yellow in color. A good beating of the egg yolks will distribute the lecithin more evenly all throughout the ice cream mixture.
Once the cream/milk mixture has cooled enough, pour it into the egg yolk/sugar mixture in a slow steady stream, while whisking constantly. We do this in order to temper the eggs.
Next, pour the tempered egg yolk mixture back into the hot cream/milk mixture. Continue heating the mixture until it begins to thicken, but never allow it to come to a boil or the eggs will coagulate. To test for doneness, using your finger, draw a line in the back of the wooden spoon that you have been using to stir the mixture. If the mixture is thick enough, the line will hold its shape. This means that the mixture is ready. Stop cooking immediately, strain the mixture and cool it rapidly to room temperature using an ice water bath.
Once ice cream mixture has cooled to room temperature, for best results, refrigerate mixture over night. The next step is churning the ice cream in an ice cream machine. After about 30 minutes of churning the ice cream should be ready. Add-ins are added into the ice cream during the final minute of churning.
Cooking the custard to 180deg. F will give you best results, while cooking the custard to 170deg. C or less will give a rougher texture to the ice cream.
Vanilla extract complements chocolate and coffee flavors.
Overrun refers to the amount of air that gets incorporated into the ice cream while it is being churned in an ice cream machine. An ice cream with 100% overrun, means that an ice cream mixture of 1 liter will yield 2 liters of finished product; ice cream. The less the overrun, the less air is incorporated into the ice cream giving you a harder, denser and heavier ice cream, while the more the overrun, the more air is incorporated into the ice cream giving you a softer, creamy and airy texture.
When the prepared ice cream mixture (that has rested in the refrigerator over night) is poured into the ice cream machine, and the machine is turned on, the compressor cools the metal container that carries the ice cream mixture to below the freezing point. This in turn begins to freeze the ice cream. The constant rotation of the rotating blades prevents the ice cream from freezing completely and at the same time air is incorporated into the mixture giving the ice cream a lighter and smoother texture.
Storing and serving ice cream
Once the mixture of ice cream is ready it should be placed in the freezer at -18deg. C. Ice cream should be served when the ice cream temperature is almost -15deg. C. The longer you wish to store a churned ice cream, the cooler the freezer should be (~ -45deg. C).
Professional ice cream machines have more air inject more air in the ice cream (than homemade ice cream machines), giving you a lighter, less icy texture. In professional ice cream machines eggs are not used, but instead a stabilizer is used.
- Too many eggs overpower the ice cream taste.
- Too much cream (or only cream) in the ice cream gives a buttery taste.
- Using only milk will promote ice crystals in the ice cream, diluted taste.
- Sugar reduces ice crystals and lowers the freezing temperature of the custard. For example, if your ice cream was frozen solid at -15deg. C, by adding more sugar, you ice cream would not freeze solid at -20 deg. C. Sugar also promotes a smoother, and softer ice cream. 3/4 cup sugar per liter of ice cream is just perfect. Less sugar than that, eg; 1/2 cup sugar will give you an ice cream that is too firm, and too icy.
- Ice cream tastes best at around 10 - 12 deg. F.
NOTE: Ice cream coming out of an ice cream machine will not come out with a firm texture. Several hours in the freezer will complete the freezing process.
For more information on the subject, and the exact quantity of ingredients used, see our step by step video tutorials on ice cream.