The ability of freezers to harden and crystallize certain liquids depends on their composition and properties. When it comes to freezing and crystallizing, several factors come into play:
Water content: Water is the primary component that freezes easily in a typical household freezer. When you freeze water, it forms ice crystals, which give the frozen substance its solid structure. Fruit juices and whipped creams also contain a significant amount of water, which allows them to freeze and crystallize similarly to ice.
Sugar content: Sweeteners like sugar and other syrups can act as "cryoprotectants," which means they lower the freezing point of the liquid. This interferes with the formation of large ice crystals, resulting in a smoother and creamier texture. Condensed milk already contains a high amount of sugar, which helps it achieve a smooth texture when frozen.
Fat content: Condensed milk contains a relatively high amount of fat, which affects its freezing behavior. Fats have a more complex crystallization process compared to water. In some cases, high-fat content can hinder the formation of large ice crystals and lead to a softer, less crystalline frozen texture.
Other ingredients: The presence of other ingredients, such as stabilizers and emulsifiers, can also impact freezing and crystallization. These additives can alter the freezing properties and affect the final texture of the frozen product.
Processing and pasteurization: Condensed milk is usually processed and pasteurized before being packaged. This process can affect the milk's structure and behavior during freezing.
Freezer temperature: The temperature of the freezer itself plays a role in freezing. Some household freezers may not maintain temperatures low enough or consistently enough to allow certain mixtures to harden and crystallize properly.
In summary, the freezing and crystallization behavior of liquids depend on their water, sugar, fat content, and the presence of other ingredients. Condensed milk, due to its high sugar and fat content and other processing factors, may not freeze and crystallize in the same way as water, fruit juices, or whipped creams without sweeteners. If you want to experiment with freezing condensed milk, you might try adjusting the fat and sugar content or using an ice cream maker, which allows better control over the freezing process and texture.