How Do You Make Ice Cream?

0:00How do you make ice cream? Hi, welcome to Curious Kids Every Day. I'm Josh. How are you doing today? It's so good to hear from you. Hey, what is your favorite flavor of ice cream? For me, it's gotta be caramel. Oh, I love caramel ice cream. We don't go out for ice cream very often, so I always end up picking caramel ice cream when we do. I always am really craving it by the time we get ice cream again. I always think, I should try a new flavor this time. Caramel is just so good. Is that how it is for you with your favorite flavor of ice cream?

1:00Is it hard to pick any other flavor? Now, one year for Christmas, my parents got me an ice cream maker, so I can actually make ice cream at home if I want. Did you know that you can make homemade ice cream? Oh, it's so good. I think it's just as good as the stuff you get at an ice cream shop. I was thinking about ice cream today because I got an email from a curious kid named Melinda. She wondered, how do you make ice cream? Now, when you reach into the freezer and grab something, that's something is usually solid, right? Have you ever noticed that? There are very rarely soft frozen things. Frozen things are usually hard.

2:02For example, water. What does water turn into when it freezes? Right, ice, and if you freeze meat like a hamburger, it gets really hard too. But ice cream, it's a little different, isn't it? You can scoop it even when it's super cold. Do you want to know why that is? Well, it's all in the way, it's mixed and frozen. See, the three main ingredients in ice cream are milk and cream and sugar. But if you just put those ingredients together and mix them up and put them in a freezer, you would not make ice cream. Not even close. There's a secret to making ice cream. And that secret is something called churning.

3:07Do you know what churning is? Churning is basically just stirring something or mixing it. The secret to ice cream is that while the ice cream is being frozen, it's being churned. The small ice cream maker that my parents got me for Christmas is basically a little circular freezer with a plastic piece in the middle that spins and mixes the ingredients in the freezer while it's freezing. That's how you make ice cream. And the ice cream you get at the grocery store or ice cream shops, they do it the same way. But they've got a few more steps along the way. Let's learn how it all works.

4:11Large companies start with huge stainless steel tanks. They pump in milk and cream and sugar and flavorings like vanilla or cacao. If the recipe uses eggs or stabilizers, those are added too. Stabilizers are ingredients that help control texture. They help keep ice crystals small and keep the frozen desert smooth during storage. Small ice crystals are one big reason it's scoopable, along with sugar and air, which keeps it from freezing into a solid block. That means the scooper can cut through even though it's still very cold. Before freezing, the liquid mixes heated to a specific temperature for a short time. This process is called pasteurization. Can you say pasteurization?

5:14Pasteurization kills any harmful bacteria that might be swimming in the ingredients. It also helps ingredients blend together more evenly. Have you ever taken a field trip to a dairy processing plant? If you have, you might have seen those big pasteurization machines. I went to one when I was a kid and the main thing I remember about it is the smell. It smelled terrible. Warm milk. After heating, the mix is cooled down quickly. And the next step is called homogenization. Can you say homogenization? This is when the mix is pushed through tiny openings under high pressure. This breaks fat droplets into very small pieces. And why does that matter? Well, smaller fat droplets make the texture smoother and prevent the fat from separating.

6:17This helps give that creamy texture that you expect from ice cream. The mixture is then chilled and held in cold tanks for several hours. This step is called aging. And it allows the fat to firm up slightly and lets protein absorb water. A lot of the reason that ice cream is ice cream is because milk has fat in it. And getting that fat to do exactly what is needed to do is what makes ice cream ice cream. Again, this improves texture and helps trap air later. Oh yeah, did you know that air is a very important ingredient in ice cream? I did mention that earlier too, but did you know that? It's true. And you're about to find out why. Because now comes the freezing. Finally, we get to the freezer.

7:23Factories use machines called continuous freezers. The cold liquid mix flows into a freezing barrel with very cold walls. And inside, rotating blades scrape frozen layers off the sides while mixing air into the batch. So the mix is constantly churning and air is being added into the mix. This is just like how it's done at home with my homemade ice cream maker, but just on a much bigger scale. Just like with my homemade ice cream maker, two things are happening at once when the ice cream is getting churned. One, ice crystals are forming, but they're being kept small. And two, air is being mixed in.

8:24But why does that air need to be mixed in? Well, air affects the thickness of the ice cream, so the amount of air added is measured carefully. And this is called overrun. Can you say overrun? Some frozen desserts have a lot of overrun, which means they have a lot of air, and that makes them lighter. Some have less overrun, and that makes them denser. You know how some ice cream, you scoop it into your mouth, and you can almost chew it in your mouth, but then other ice cream is a lot softer, like soft-serve ice cream. Soft-serve ice cream has a lot of overrun. They add lots of air. Now, you can get lots of different flavors of ice cream. And some flavors of ice cream have little extra ingredients in them, right?

9:27Things like chocolate chips or cookie pieces. Those kinds of things are added in after the freezing stage, but while the mixture is soft, but thick, special machines fold them in evenly without crushing them. Finally, the packaged dessert moves through a blast freezer. This freezer is much colder than a home freezer, often around negative 20 degrees Fahrenheit or even colder. This hardens it quickly and locks in the tiny ice crystals. Then it's stored cold and shipped to stores. Phew, that's a lot! So, factory-made ice cream follows the same science as homemade. You've got to control the ice crystal size, you've got to mix in air, and it has to be churning while it's freezing. It's all very precise because, instead of me making one bowl at my house, they might make thousands of gallons in a single day,

10:33and every scoop has to feel and taste the same. And that is how you make ice cream. Okay, let's have a quick quiz. What is the process called when factories heat the mix to kill harmful bacteria? That's called pasteurization. And what process breaks fat into tiny droplets to make the texture smoother? That is called homogenization. And what is the name for the measured amount of air mixed in during freezing? We call it overrun. All right, let's play true or false. True or false, homogenization makes fat droplets larger so they're easier to see.

11:40No, that's false. True or false, adding air during freezing can make a frozen desert lighter in texture. Yes, that's true. True or false, a blast freezer is usually colder than a regular home freezer. That is true too. I would really recommend if you can go to a dairy processing plant or even just a milk farm, just to see where all the milk comes from and how it's processed before it gets to the store, it's all very, very interesting and a lot of fun to learn about. So maybe you can take a field trip to do that soon. It's so cool. Would you rather eat ice cream for every meal or once a day? I would say I would rather eat ice cream once a day because ice cream too often will upset the stomach, so I'll go with just once a day. A little ice cream goes a long way for me.

12:43All right, let's play around of what am I? What am I? I measure how much air is added during freezing. I change how heavy or light a scoop feels. And factories calculate me carefully. What am I? I am overrun. Okay, we're going to play a quick game called Can it be an ingredient in ice cream? Now you can put whatever you want in ice cream, I guess, but just the things that would normally go in ice cream that you can imagine going into a regular ice cream. You tell me yes or no, can these things be ingredients in ice cream? Are you ready? Can milk be an ingredient in ice cream? Yes, what about spinach? No, what about sugar? It's hard to make ice cream without sugar. What about mustard?

13:46No, what about strawberries? Definitely. What about egg yolk? Yes, it can be a stabilizer. What about ketchup? No, what about broccoli? No, what about cinnamon? Ooh, cinnamon flavored ice cream, that sounds delicious. Well, now when you take a bite of that cold, creamy goodness, you can picture what had to happen for it to feel that smooth. Isn't it neat that they have to measure the amount of air to make sure the consistency is just right? And it only works if it's being continuously churned while it's freezing. So what flavor are you going to get next time? I promised my son that the next time we go get ice cream,

14:48I would get a flavor other than caramel, so that's what I have to do. Maybe I'll go with strawberry next time. Mm, strawberry ice cream. What kind of question do you think we'll ask tomorrow on curious kids every day? I can't wait to find out. So until then, keep asking questions and stay curious, kids. And we've got a few birthdays today. Today is Ray's birthday. Ray is from Canada and Ray is turning 5. Happy birthday, Ray. Auto is from Wisconsin and auto is turning 5. Happy birthday, auto. William is from Oklahoma and William is turning 6. Happy birthday, William. And Ellie is from China and Ellie is turning 9. Happy birthday, Ellie. For all the grownups listening, if you're curious kid wants their birthday mentioned on the show, please visit supportcuriouskids.com and join the Curious Kids Club. That supportcuriouskids.com. See you tomorrow.