Just about everyone loves cold, sweet, creamy ice cream. I’ve done quite a lot of ice cream reading and making. But when I wanted to learn as much as possible about it, I decided to go to ice cream college, or more specifically, the famous (in ice cream circles anyway) Ice Cream Short Course at Penn State University. Every January for the last 126 years, over a hundred people gather to learn just about everything there is to know about ice cream.
What defines ice cream?
Scientifically, ice cream is a partially-frozen emulsion of fat, sugar, protein, and air in water. Sounds delicious, doesn’t it?! Believe it or not, the U.S. has a legal definition and the FDA specifies which frozen desserts are allowed to be called “ice cream” so you know what you’re buying. How much milk fat and milk protein, the minimum weight of a gallon, its pasteurization, freezing methods, sweetening, and flavors are all part of the ice cream definition.
Although the FDA defines ice cream, it doesn’t say a whole lot about what it actually is. There are seven main components of ice cream: water, milk fat, milk proteins, sugar, air, stabilizers, and emulsifiers. Each ingredient has a specific purpose and amount. Coming from milk and cream, water is the most abundant ingredient and makes up 60 to 65% of the ice cream’s total weight. Everything in the ice cream is either dissolved or suspended in water, with much of the texture of ice cream coming from the ratio of liquid to frozen water.
Milk fat adds flavor and texture while contributing to the cold sensation you get when eating ice cream. The percentage ranges from 10 to 20%. As it is the most expensive ingredient, it is the main element that defines the quality of the ice cream. Super premium brands like Häagen Dazs or Jeni’s will have 16 to 20% milk fat, while store brands will likely have only 10%, the minimum amount the FDA allows (unless the package specifies low fat).
8 to 12% of the weight of the ice cream is from milk proteins, which add flavor and powerful emulsification. They coat both the fat droplets and the air pockets in the ice cream, allowing both to be dispersed in the water. If you have ever had ice cream that leaves a greasy feeling in your mouth, it could be that there wasn’t enough protein to ensure the fat droplets stay small and dispersed. The ice cream could also be over churned, which physically strips the proteins from around the fat droplets. This allows them to coalesce and make fat globules large enough to feel in your mouth.
Sugar is another very important component in ice cream, making up 12 to 20% of the total weight. Beyond the obvious sweet flavor that sugar adds, it is also essential in depressing the freezing point and allows the ice cream to have a freezing range. Pure water has a freezing point, meaning that at 33 Fahrenheit (F) it is liquid, but frozen solid at 32F. Ice cream should not be either liquid or solid like an ice cube, which means it should have a freezing range a few degrees above and below the temperature at which we would like to eat it. The hardness of the ice cream will be determined mainly by the ratio of liquid to solid water, and good ice cream with a proper texture is a mixture of liquid water and solid ice.
Air is the cheapest ice cream ingredient, but it is no less important! Ice cream is agitated while being frozen, which incorporates air. The amount of air in ice cream is called “overrun.” Proteins and added emulsifiers coat the air bubbles and help them stay dispersed in the ice cream. Lower quality ice creams have more air in them, sometimes up to 100% overrun, meaning that the air makes up half of the volume. Higher quality and higher fat ice creams incorporate less air and are denser, with overrun as low as 20%.
Stabilizers and Emulsifiers
Stabilizers and emulsifiers (SEs) are currently rather controversial ingredients among consumers. Even though the popular press often touts SEs as dangerous and added by big companies to make more money, they are completely safe -- most are isolated from plants like seaweed or soybeans. They’re also critical to making high-quality ice cream. The amount of fat and air incorporated into ice cream play a very important role in the texture and “scoopability.” Without them, you can easily end up with a soupy mess or a block of ice. SE’s help coat the fat globules and air pockets to keep them in suspension, and they also help to control the water.
Smooth ice cream has tiny ice crystals that are too small to feel in your mouth. As the temperature of the ice cream fluctuates during shipping, purchase and storage (yes, even in your freezer), some amount of the ice melts and refreezes, making larger ice crystals. You may have experienced this when tasting a forgotten (and potentially crunchy) pint of ice cream from the back of the freezer. SEs actually help to bind the water and ice crystals in the ice cream, separating them and limiting the growth of those ice crystals during freezing and thawing. This helps to maintain a soft texture and allows cold ice cream to be soft enough to eat with a pleasant mouthfeel. Häagen Dazs, for example, makes a very high-quality and tasty ice cream. A major selling point is that they do not use SEs. However, when you take it out of the freezer to eat, it’s very difficult to scoop!
With this knowledge, you can evaluate different ice cream brands based on what is most important to you. Do you like rich, firm, and creamy ice creams? Or do you like fluffy, lighter ice creams that remind you of your childhood and are perfect for scooping into cones? Moral of the story: you may want think about these components and look beyond flavor as the main method for choosing your ice cream...or make your own! Check out my recipe for sous vide, liquid nitrogen ice cream here!