Ice cream science: Make a cool treat to beat the summer heat

It’s getting to that time of year when it’s so hot and yucky outside that everything cold is better.

It’s also a time for telling kids about how, when you were their age, if you wanted ice cream you had to turn a crank until your arms fell off (presumably while walking uphill to school both ways and fighting off bears…).


Here in the Houston Museum of Natural Science education department, we have tried making ice cream in a variety of ways to see what is easiest for kids, and not all ways are equal. (Pro tip: Those special ice cream-making balls they sell for kids freeze shut, and then kids are sad. Not recommended.) Our favorite way, at the end of this post, is fairly cheap and easy and fun for kids, but before we get to the instructions, let’s talk about some science.

To make ice cream, you will of course need ice. The ice is simply to lower the temperature of the cream to the freezing point, but if you just used ice alone and let it sit, you’d end up with a solid block of cream – more like an ice cube – and it would take longer to freeze. What makes ice cream special is salt and stirring.


Water freezes at 32° F, but sprinkling salt on the ice lowers the freezing/melting point of water. How, you say? In order for liquid water to freeze to solid ice, all of the water molecules have to slow down enough to connect to each other and form solid crystals. When this happens, the water loses kinetic energy due to the decrease in movement of those molecules. Because temperature is a measurement of kinetic energy, this results in a lower temperature.

The presence of salt interferes with this process. The water molecules can’t attract each other as easily because they are also attracted to the sodium and chloride ions from the salt. Mixing the salt, ice, and water together results in a temperature below the freezing point of water, which helps the cream freeze faster. The shaking or stirring helps cool the cream evenly and efficiently. In ice cream, this lower freezing point turns the fats into solids, but the water content to be almost frozen.


What about the milk, then? It is much easier to make ice cream with creamer, heavy whipping cream, or half-and-half than to use skim milk because of the higher fat content in cream. You can make ice cream with skim milk, but it is really, really, really hard to do by hand, AND you have already committed to making ice cream, so I feel like you have acknowledged the inherent risk of fat consumption that comes with making a frozen confectionery delight. Just use the full-fat stuff, and let’s all move on.

What does the fat do, anyway? Primarily the higher fat content allows for a richer, creamier texture and a more delicious flavor in your finished product. The reason for this is that when you are cooling and mixing the cream, you are also introducing air molecules to the liquid. The bits of fat in the cream add a little structure to the ice cream and trap these air molecules in the solution as it forms. This, plus the lower freezing temperature, enables you to be able to scoop the ice cream fairly easily because it allows for there to be a bit of unfrozen water in the ice cream, which stops the ice cream from becoming a solid block of ice.


If you have ever had ice cream that has grown ice crystals and gotten a bit of freezer burn, those ice crystals appeared because the unfrozen water in the ice cream had a chance to migrate a little bit when the ice cream was warmed slightly on the ride home or when it was left on a counter a little too long and then frozen again. There are things called stabilizers added to your ice cream to prevent this from happening. Most ice creams today have one of five stabilizers added to them: carob bean gum* (a type of bean from Africa), carrageenan (a type of algae), guar gum (a type of legume from India), sodium alginate (made from seaweed) or carboxymethyl cellulose (sounds scary but it’s plant-based). Often, if you read the label, you will see more than one of these in your ice cream to keep it smooth and delicious.


* Carob beans, or locust beans, are cool. They are from exotic African trees and each bean is so similar that at one point they were used as a unit of measurement for gold and silver. We still use this measurement today, but the name has changed over time to Karat.

So now that you have had a little lecture about the science of ice cream, let’s get to the delicious lab work.


Activity: ICE CREAM!!!!


Individual serving containers of coffee creamer


Small waterproof container or quality sealable plastic sack big enough for about two or three cups of chipped ice

Salt, any variety

A dish towel to insulate your hands

Optional: Inexhaustible energy of small child-based labor



  1. Find some liquid coffee creamers in individual pots.
  2. Put ice in your water proof container, filling it about a third of the way. Smaller chunks of ice work better because there is more surface area, but any ice will do.
  3. Layer your salt on your ice. Several solid sprinkles will do, but if you are nervous about the quantity, add some extra just in case. It won’t hurt anything.
  4. Put your sealed creamer cup(s) in your container and then put more ice in, filling it about 2/3 of the way.
  5. Layer on more salt.
  6. Finish filling the container with ice.
  7. Start shaking your container. Make sure it is well sealed and that you have a firm grip on it. No one wants to be injured in an ice cream-related accident. There is no way to spin that so it sounds cool. Also, this is an excellent job for kids to help with. Put on a nice, long song or two and let them wiggle till they drop. About ten minutes will do it, but you will know when you are getting close because a frost will form on the outside of your container. If you don’t feel frost forming after a couple of minutes, add more salt. To speed this process up, start with creamer pods that have been stored in the fridge. This way, your creamer will start at about 50° F, and you won’t have to work so hard.
  8. After about 10 minutes of shake, shake, shaking your ice cream, dig your creamer cup out of the ice and wipe it off.
  9. Ta dah! You are done. Unless you want to make this tablespoon of delicious homemade ice cream into a sundae and add chocolate and banana or some jelly for more flavor.


Note: If you are thinking to yourself, “That seems like a lot of work for a tablespoon of ice cream,” well… it is. But it’s also science. So there.

If you get the liquid creamer that comes in a larger container at the grocery store, you can increase the volume of your creamer and make MORE ice cream. If you choose to do this, you will need to find a small waterproof (and I would suggest plastic) container to pour the creamer into and then a slightly larger waterproof container for all the ice and the salt. It’s the same procedure, just with a larger amount of the ingredients!



You Can Thank Science for Helping You Cook an Awesome Thanksgiving Dinner

Loosen your belts boys and girls, because we are approaching Thanksgiving, the day where diets and portion control cease to exist. To make things a bit easier for you, I have compiled some tips on how to make your Thanksgiving dinner a winner. And how do we do this? With science of course!

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When it comes to cooking turkey, the star of your Thanksgiving dinner, you have to make sure your bird comes out moist, tender, and flavorful. First thing to know is the cooking style and time depends on the parts of the turkey you are cooking. If you are going Ren-Fest style and just serving up turkey legs, a longer cooking time at a low temperature would be better to allow the tissue to break down slowly. However, if you are just serving up a turkey breast, it can be cooked at a higher temperature for a shorter period of time since there is not as much tissue as is in the legs.

Now I am going to assume that you are a Thanksgiving champion and are cooking the whole turkey. Here’s what you should do to make a winner winner turkey dinner:

  • As mentioned above, the breast and legs have different cooking times, however if you are cooking the whole turkey, this isn’t really an option. However, there is a way you can help differentiate the cooking times before putting your turkey in the oven. “Take the bird out ahead of time and let the legs warm up a little bit while you keep the breasts covered with ice packs. That way, you keep the breasts cold. The legs warm up by maybe 10, 20 degrees, and that way, when you put the bird in the oven, you’ve already built in a temperature differential. The breasts are going to end up, at a given time, less-cooked than the legs.“ – NPR- “Delicious Turkey Tips From Food Scientists
  • We have all had that dry, chewy turkey before, and I don’t know about you, but I would rather not repeat that experience. To help your turkey maintain its moist deliciousness, soak your bird in a saltwater solution prior to cooking–aka brining. Brining helps loosen the structure of the muscle fibers and increases the turkey’s water weight, these steps combined result in tender and juicy meat. Check out Butterball’s brining guide to find the correct brining time for your turkey.
  • If you are roasting the turkey, cook it on an elevated rack a few inches off the bottom of the pan to allow the heat to circulate evenly around the turkey. If your turkey is resting on the pan, the heat will not be able to fully circulate resulting in an unevenly cooked bird.
  • Have ever cut your turkey (or steak, too) while it is hot and seen the juicy deliciousness seeping out? Well, sorry my friend, but you are watching the flavor leave your meat. When your meat is still hot, the juices are still flowing and have not rested into the fibers yet. Therefore, you should allow your turkey to rest prior to carving. The rest time depends on the size of your turkey and can be anywhere from 5-20 minutes. Letting your bird rest will also make for easier carving.


  • Green beans
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    Blanching green beans brings out their vibrant green color, but you may have noticed that their color dulls over time. This is “a result of the chlorophyll molecules losing their magnesium ions in the heat.” To stop this, shock the beans with an ice bath immediately after they finish cooking.
  • Pie 
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    Who knew the secret to a flaky, yet easy to work with crust was vodka? When rolling out pie dough, water is often added to form a more cohesive crust that is easier to place into the pan. This is fine up to a certain point. Adding too much water will activate the gluten development causing the dough to lose its flakiness. However, vodka will add the extra moisture you need without activating the gluten development. (Don’t worry your pie crust won’t taste like vodka.) Source – Live Science
  • Stuffing
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    While cooking stuffing in the turkey is tradition, you may want to rethink that. Most stuffing mixes contain eggs which need to be brought up to a temperature of 165 degrees Fahrenheit in order to kill the bacteria. In order for the stuffing temperature to reach 165 degrees Fahrenheit, you risk overcooking the turkey and drying out the meat – not cool. Instead cook the stuffing on its own and serve it on the side or add it to your turkey platter after the turkey has been cooked.
  • Rolls
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    Rolls are one of the best parts of Thanksgiving in my opinion, but making it is not. If you’ve had homemade rolls you know there is nothing that you can get out of a box, carton, or frozen package that compares to the delicious fluffiness of homemade rolls. No one has the time, especially on Thanksgiving, to endlessly knead bread. Unfortunately, kneading is a necessary step in the break making process to “break down existing bonds and form stronger, straighter gluten sheets.” However, you can save your hands five minutes of kneading thanks to autolyse – i.e. let the dough rest before kneading (about 20 minutes). The resting time allows for the existing bonds to break down on their own. 

    Now get ready Thanksgiving, because we are coming for you!
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Chemistry in the Kitchen: The Science Behind Ice Cream

Legend has it that the Roman emperor Nero discovered ice cream. Runners brought snow from the mountains to make the first ice cream.

Making ice cream at home is easy – no mountain marathon required! Just read the instructions below and enjoy your very own homemade ice cream.

 Creative Commons LicensePhoto Credit: Jessicafm

Rock salt
Pint-size baggies – heavy duty
Gallon-size baggies – heavy duty
Measuring cup
Measuring spoons

1. Fill the large bag about ½ full of ice.  Add 6 tablespoons of rock salt to the ice.

2. Put ½ cup of milk, ¼ teaspoon of vanilla, and 1 tablespoon of sugar into a smaller baggie and seal.  Put this inside another small baggie and seal.  This will prevent saltwater from seeping into your ice cream.

3. Place the double bagged small baggie into the larger baggie and seal.

4. Shake the baggie until you have ice cream. 

5. Remove the smaller baggie from the larger one.  Wipe off the water, then open it carefully and enjoy your ice cream! 

UPDATE: Check out our Science of Ice Cream video to learn more!

Chemistry in the Kitchen: The Science Behind Butter

 Photo credit: booleansplit

People have been enjoying the rich and wonderful taste of butter for more than 6,000 years.  Archaeologists have found pounds of ancient butter buried in the peat bogs of Ireland.  Butter is still made in essentially the same way as it has been for thousands of years.  Roll up your sleeves and make butter like the ancients!

Heavy whipping cream – you can buy this at the grocery store
Crackers – any kind you like
Clean baby food jar
Butter knife

1. Fill your baby food jar about ½ full with whipping cream.
2. Add a pinch of salt for taste.
3. Seal the cap on tight.
4. Shake your jar up and down vigorously.
5. You will notice that soon you will have a creamy substance that we know as whipped cream.  You’re not done yet!  Keep shaking!
6. Soon you will have a clump surrounded by a liquid.  The clump is your butter and the liquid is buttermilk.
7. Drink the buttermilk if you like, it’s full of protein.
8. Place your butter in a piece of cheesecloth and squeeze the excess liquid out.
9. Use your butter knife to spread your creation on crackers and enjoy!

When milk straight from the cow is left to stand it separates into skim milk and cream.  The cream rises to the top.  The cream is full of proteins and fat.  When you shake the cream and agitate the fat globules, they stick together to form butter.  The leftover liquid is called buttermilk and it is full of protein. 

Interested in learning more about cooking and the science behind it? BEYONDbones will be bringing you The Science of Food – a series of videos exploring the science involved in the culinary creations of some of the best chefs in town. Its all part of Big Bite Nite on April 30, an event featuring food from over 30 restaurants all in one location – HMNS.