The Science Behind: Ice Cream
Happy National Ice Cream Day!
Since today is the third Sunday of July, National Ice Cream Day, I have been left with no choice but to write about the science behind ice cream.
Ice cream is made of five basic components: air, sweeteners, fat, ice crystals, and other solids.
Typically, air makes up 30%-50% of ice cream’s total volume. Air prevents an overly sweet flavor while creating structure. The better its structure is, the more time it will take for the flavor molecules in the ice cream to be released, making the flavor last longer.
Sweeteners are crucial to an ice cream’s flavor and quality because cold foods tend to numb your taste buds, making them less sensitive to flavors. To address this, more flavorings must be added. Sweeteners add sweetness, of course, and improve the texture and body of the ice cream while lowering its freezing point, so when you freeze the ice cream, you aren’t left with a tasty rock.
The main reason why ice cream tastes so devilishly delicious is its high fat content. Ice cream must be at least 10% fat — unless it’s labelled as low-fat, non-fat, or light — and this fat must come from milk. Fat adds richness, increases flavors overall, and improves the density and smoothness of the ice cream.
Ice crystals are created when the water contained in ice cream starts to freeze. The size of these crystals determines whether the ice cream will be smooth or grainy. To avoid creating sandy ice cream, these crystals should be small.
Although the title other solids is rather frightening, it simply means things like chocolate chips, mineral salts, stabilizers (proteins that prevent large ice crystals while absorbing and locking the liquids in ice cream in place), cookie dough, and fruit. These all contribute to the body, texture, and smoothness of the ice cream. When there are more solids, there is less free water, which leads to fewer ice crystals, but if there are too few solids, then the ice cream will be sandy.
Now, with all these components, it’s time to make ice cream! First, the base is prepared. Milk, cream, sweeteners, and other solids are mixed together. Next, the base is pasteurized to eliminate any dangerous bacteria. The base moves on to homogenization. Apart from being quite a mouthful, homogenization is the process in which the fat droplets in the base are broken up and dispersed. This is done to create an emulsion.
The problem with fat is that it doesn’t get along with most substances, including water, which is in basically everything. To keep the fat and water in ice cream together, an emulsion — a combination of two liquids that normally don’t mix where one of the liquids is dispersed throughout the other — must be created. To accomplish this commercially, the base is typically forced through a narrow slit at high pressure, breaking up the fat droplets and dispersing them throughout the mixture. Each fat droplet is then coated with a layer of milk proteins, one of fat’s few friends, which prevents the fat from clumping together. Lecithin, a substance found in egg yolks, inserts itself between the fat and proteins and helps them combine. The base cools to fridge-temperatures and is given time to age and mature, greatly improving the texture, smoothness, and stability of the ice cream.
The base is pumped into a metal barrel surrounded by a refrigerant while a stream of air is introduced into the barrel. Then, the mixture is churned, creating ice cream. Or, if you want to be a thug, you could skip this entire step and just add some liquid nitrogen. Finally, the ice cream is put in the freezer until it is ready to eat. Bon appétit!
Rohrig, Brian. “Ice, Cream… and Chemistry.” American Chemical Society, Feb. 2014, www.acs.org/content/acs/en/education/resources/highschool/chemmatters/past-issues/archive-2013-2014/ice-cream-chemistry.html. Accessed 16 July 2017.
“The Science of Ice Cream.” Ice Cream Nation, www.icecreamnation.org/science-of-ice-cream/. Accessed 16 July 2017.
— Isabella S., Pennsylvania