Science Behind Ice Cream Revealed

Maya Warren, a prior PhD student at the University of Wisconsin-Madison and member of the Institute of Food Technologists Student Association (IFTSA) explains how food science plays an important role in the creation of ice cream. From coming up with different ingredients and flavors, to making sure it stays fresh in your freezer, food scientists are hard at work creating a product that is fun and tasty.

What is ice cream made of?

Ice cream is made up of a few main ingredients: cream, milk solids, sugar or a sugar-type replacement, and water. When developing commercial ice cream products, scientists sometimes add gums to give the ice cream more body and help impede excessive ice crystal growth. Emulsifiers (like egg yolk) are also added which contribute to the creamy mouth feel of ice cream.

How is ice cream made?

• The basic ingredients are mixed and blended in a mixing tank. The mixture is then pumped into a pasteurizer, where it is heated, a food safety precaution in order to kill remaining harmful bacteria. The hot mixture is then "shot" through a homogenizer, where pressure of 2,000 to 2,500 pounds per square inch breaks the milk fat down into smaller particles, allowing the mixture to stay smooth and creamy. The mix is then quick-cooled to about 40°F and frozen.

• During freezing, the mix is aerated by "dashers," revolving blades in the freezer. The small air cells that are incorporated by this whipping action prevent ice cream from becoming a solid mass of frozen ingredients. The amount of aeration is called "overrun," and is limited by the federal standard that requires the finished product must not weigh less than 4.5 pounds per gallon.

• The next step is the addition of bulky flavorings, such as fruits, nuts and chocolate chips. After the flavoring additions are completed, the ice cream can be packaged in a variety of containers, cups or molds. It is moved quickly to a "hardening room," where sub-zero temperatures freeze the product to its final state for storage and distribution.

Why does homemade ice cream taste so much different than store bought?

Making ice cream at home versus commercially produces very different results, which has a lot to do with the freezer and the freezing process. At home the ice cream freezing process can take up to 30-45 minutes, and commercially-made ice cream is usually frozen in 30 seconds or less. The longer freezing time causes the ice cream to have much larger ice crystals which makes it have a less-creamy mouth feel.

What’s the difference between economy and premium ice cream?

Economy brand ice creams and premium brand ice creams have different levels of milk fat and air in them. To be legally called ice cream in the United States, it must have 10 percent or more milk fat. Economy brand ice creams will have at least 10 percent milk fat, and premium ice creams will have over 15 percent milk fat. The premium ice creams tend to have less air, so the product is denser. For example, if you compare a pint of $5.99 ice cream to a pint of $2.29 ice cream, you’ll see that the $5.99 ice cream is quite heavier, which is because of those differences in air.

How is low-fat or fat-free ice cream made?

Fat-free or low-fat ice creams are frozen at a lower temperature faster that create smaller ice crystals so when it hits your palate you perceive it to be just as creamy as fuller fat ice cream. In addition, those products may have added stabilizers and fat replacers to replace the missing fat and add bulk.

What’s the best way to keep ice cream tasting fresh?

• When you go to eat ice cream from your freezer, don’t let it sit out, take some scoops right away and stick it right back in your freezer. The more ice cream thaws and then freezes again, the larger the ice crystals become which can give the ice cream an icy/course feel and a freezer-burn taste.

• The best way to store ice cream is in a tightly-sealed, closed container, preferably plastic or in a cardboard carton that has some thin plastic lining so the container doesn’t become soggy. Although adding some plastic wrap on the top may extend the shelf-life a little bit longer, try and eat your ice cream within a week of purchasing it for maximum freshness.

Source:
Maya Warren, PhD candidate, University of Wisconsin-Madison
International Dairy Foods Association