See the German-language version of this piece at Spektrum der Wissenschaft.
People have been enjoying ice cream for hundreds of years.
But there have never before been as many flavors as we enjoy these days. From sweet to savory, the ice’s cream wondrous variety is all due to chemistry.
Ice cream is a heterogeneous mixture of a liquid and finely dispersed solids. That is why it is called a complex colloidal system.
Each part in this system has an important function. Air bubbles typically make up about 30 to 50 percent of the mixture’s final volume. They alleviate the feeling of cold and provide suppleness.
If the air content is too low, the ice cream becomes hard. If it is too high, the treat becomes too frothy and loses its taste.
Fat droplets make ice cream creamy. Proteins from milk form around the fat, a combination that helps to separate the droplets and stabilize the mixture.
Liquid sugars surround the insoluble particles. They determine sweetness and softness. In food science, the sweetness is recorded using a scale called “potere dolcificante” (“sweetening power”), or POD. That part of sugar’s contribution is obvious.
Less obvious is the fact that sugar lowers the freezing point of water, reducing the amount of ice that forms in the mixture. It therefore has “antifreezing power,” which is also called “potere anticongelante,” or PAC.
The sugar sucrose sets the standard for PAC, which corresponds to how much the freezing point is depressed by, say, one pound of sucrose dissolved in 100 pounds of water. Ice cream manufacturers use many more sugars. The lower the serving temperature, the more sugar is needed for creamy ice cream.
Professionally produced ice cream has a serving temperature of 12.2 degrees Fahrenheit. This corresponds to a PAC value of approximately 270.
In gastronomy, the serving temperature of ice cream drops to 1.4 degrees Fahrenheit, so the PAC value must be higher to get the perfect softness. The recommended PAC is between 400 and 420, which essentially affects the sugar content.
For 2.5 pounds of ice cream, we recommend this recipe. The result is a PAC of 390 and a POD of 320 at serving temperature.
But there is more than just sugar, fat, ice and air in your scoops. In addition, there are neutral components, such as emulsifiers and stabilizers. They bind solid components or fats with water and thus influence the consistency.
Locust bean gum and xanthan gum are most commonly used. The latter is obtained during the fermentation of sugar-containing substrates and serves as a thickening and gelling agent.
For a long time, the ice cream industry expanded the palette of flavors. Now the focus is on less caloric and less sweet concoctions. To achieve this, sugars are replaced with polyols, and fats are replaced with inulins.
The production of these new ice cream varieties is limited so far, but it is expected that they will soon become established.
This means maximum joy!