Ice Cream Chemistry

Learning about science often means learning lots of new words. Don’t worry – you can use the glossary at the end of the story to help you understand them. There, you can also find lots of cool videos and websites that are related to the story, and some fun questions to help you learn more. Happy reading!

This is Dr Maya Warren. She’s a food scientist from Missouri in the United States of America.

A young woman of colour with long black hair. She is wearing a white shirt and blue cardigan. She is a food scientist, Dr Maya Warren.

A food scientist is a special type of scientist, who works on producing and testing different foods. Some food scientists focus on developing new flavours or textures, while others make sure that foods are safe for humans to eat. The work of food scientists goes into every bit of manufactured food that you eat.

Maya has one of the coolest and sweetest jobs around – she’s an expert in the science of ice cream!

To you, ice cream is probably just a delicious treat; something that you eat on hot days or for dessert in restaurants. While Maya loves to eat ice cream too, she sees it as something more.  Her job is to understand all the tiny chemicals that make up ice cream and what it is that makes it taste so good.

In Britain, we eat around 337 million litres of ice cream every year – that’s more than 5 litres per person! We eat ice cream at home, in cafés and restaurants, from corner shops and vans, and are lucky enough to have an incredible number of brands and flavours to choose from.

All those types of ice cream are different because of their chemistry – and that’s something that Maya finds absolutely fascinating.

A text box. It reads:
What is ice cream?
The world is made of chemicals. From the plants outside your window, to the clothes you’re wearing, and even the food you eat, chemistry is everywhere!
Ice cream is made from four basic ingredients: 
⮚	water
⮚	cream
⮚	sugar
⮚	air
A typical scoop of vanilla ice cream will contain 
30% ice, 5-15% cream, 15% sugar solution, and
 40-50% air! 
Each of these ingredients is a substance in its own right, with its own particular chemistry. To make ice cream, they are combined, and become transformed from individual substances to one new mixture.

Maya knows that there’s much more to making good ice cream than just putting some cream in the freezer. It’s a complicated process, with lots of steps. The key ingredients – ice crystals, fat, sugar, and air – need to be put together in a very special way.

Think about what makes the perfect ice cream. Obviously, it needs to be delicious, but that’s not all. It needs to be solid but still soft, smooth and creamy. It needs to be frozen, but not at all icy. And it needs to melt as you eat it, but not so fast that it turns to liquid. Creating the perfect ice cream is quite a balancing act! The work of scientists like Maya makes sure that your ice cream ticks all of these boxes.

To understand how to make the best ice cream possible, Maya relies on two of the most important principles in chemistry: her knowledge of states of matter (solids, liquids, and gases), and her understanding of properties.

A text box. It reads: 
Let's talk about states!
The three states of matter are solids, liquids, and gases. Everything on Earth falls into one of these groups. Rivers are made of liquid water, the rocks around them are solid stone, and the wind rushing past is made up of different gases. Luckily, each state has a few key features, which we can use to identify them. 
Solids: keep their shape, can be held, always take up the same amount of space, can be cut or shaped. 
Liquids: change their shape to match the container they are in, not easy to hold, can flow or be poured easily, cannot be cut or shaped. 
Gases: spread out and change shape to fill the container they are in, cannot be held, can flow, expand, and be squashed, cannot be cut or shaped. 
Can you think of examples for each state?
States of matter aren’t fixed. When the temperature changes, matter can change state. Ice cream is a solid when it’s in the freezer, but if it’s left out on the side for too long it will quickly become a puddle of liquid!
When it comes to ice cream, freezing and melting are what scientists like Maya are most concerned about. These processes can affect the texture of the ice cream and how long it lasts for.
Changes in state are caused by four processes: freezing, melting, evaporation, and condensation. As temperatures decrease, gases condense into liquids. At even lower temperatures, liquids become solids by freezing. Turn the temperature back up, and solids melt into liquids. Even higher, and the liquids evaporate into gases.
When it comes to ice cream, freezing and melting are what scientists like Maya are most concerned about. These processes can affect the texture of the ice cream and how long it lasts for.

To make the perfect ice cream, Maya needed to know how each individual ingredient affects the final mixture. The properties and state of each ingredient makes a lot of difference!

Below, there is a table from her notebook, where she keeps track of everything that she knows about each ingredient.

Using what you’ve learnt about the chemistry of ice cream, try to fill in the “State of Matter” and “Properties” columns yourself!

A table with four columns: ingredient, state of matter, properties, and effect on ice cream. The state of matter and properties columns are empty, so that you can fill them in. The first row has the ingredient of ice crystals. Their effect on ice cream is being what freezes and makes the ice cream cold. The next row is fat (e.g. cream). This adds richness to the ice cream, increases the density of the mixture and makes it smoother. It also increases flavour. The next row ingredient is sugar (e.g. syrup). This adds sweetness and lowers the freezing point of the mixture to keep the ice cream at a scoop-able texture even at very cold temperatures. The last row ingredient is air. This is responsible for the consistency of ice cream, and has a big effect on its texture. It also increases the volume of ice cream that is produced.

What Maya didn’t know, is how these ingredients differed between brands of ice cream, and what effect that had. So, she set out on a scientific mission: to compare eighteen different brands of vanilla ice cream from the USA, and find out how each brand created their ice cream mixture.

Dr Maya Warren, holding a spoon in one hand and an ice cream (scoops in a cone) in the other hand. She is surrounded by 18 tubs of vanilla ice cream, which all look slightly different.

First things first: good ice cream needs good ingredients. Maya knew that the quantity and quality of the ingredients which different ice cream brands used would make big difference to the end result. 

Looking across all the different ice cream brands, Maya found that there was variation in the size of ice crystals and the amount of air that was in each one. The highest quality ice creams had the smallest ice crystals and air bubbles, making them deliciously dense and creamy.

“That makes sense”, Maya thought. “If the ice crystals are too large, they’ll interfere with the ice cream’s smooth texture – you’d have to crunch them as you eat!”

Maya likes her ice cream smooth, but she found that some brands of ice cream are a little bit icy. This is because they contained more water. Ice cream with a higher water content, and lower milk or cream content, is cheaper to produce. This is perfect for budget brands, but the trade-off is that ice cream with more water has larger ice crystals.

A large freezer with double doors; the kind you'd find in supermarkets. Inside it are lots of different tubs of ice cream. They are different shapes and colours, showing that they come from different brands and are probably different flavours.

The process of making ice cream also makes a big difference to how it looks and tastes. Maya decided to investigate the process behind making each of the eighteen ice creams, including the equipment that different companies use to make it.

Making ice cream to sell is very different to making ice cream at home. It involves huge industrial ice cream makers, which can churn out over 100 litres of ice cream per hour!

A text box. It reads: 
How is ice cream made?
All industrial ice cream makers go through similar steps to make their ice cream. As well as making it as delicious as possible, they need to make sure that it is safe to eat, and that it will survive being transported to shops and homes. 
There are five key steps to the process:
1.	Preparation – the ingredients are blended together to form a mixture.

2.	Pasteurisation – the mixture is heated up, to kill any harmful bacteria that might be lurking in any of the ingredients.

3.	Mixing – the mixture is churned to activate all the chemicals in the ingredients and make them react to form a new substance – ice cream!

4.	Freezing – the mixture is pumped into a very cold container. Ice crystals form at the edges of the mixture where it touches the container, and are churned through the ice cream mixture to freeze it. At the same time, a stream of air is whipped into the mixture, giving it a soft and fluffy texture.

5.	Hardening – the mixture is left in a freezer to become fully frozen and ready to sell!
As you can see, the process is much more scientific than just putting the mixture into a freezer! All these steps contribute towards the final texture of the ice cream, and what properties it will have.

Maya noticed that ice cream was frozen much more quickly in factories than in her freezer at home. It took the industrial freezers less than 10 minutes to freeze the ice cream – super speedy! Freezing the ice cream at lightning-fast speeds means that large ice crystals don’t have time to form, keeping the overall texture smooth and silky.

She was also amazed by how quickly the mixture was churned. A constant stream of air was introduced to the barrel, making sure that all of the mixture became aerated and soft. Without this, the ice cream would be very solid and difficult to eat – hard like ice, rather than fluffy like mousse.

Maya was fascinated by how many steps were important in creating the perfect ice cream texture. Without these complex scientific processes, industrially-produced ice cream would be very different.

“So”, Maya thought, “that’s the ingredients and process covered. But what about the ice cream itself?”. She wanted to know how all of the different ice cream brands differed in taste.

A text box. It reads: 
We know what food tastes like because of thousands of taste buds 
on our tongue. These tiny structures detect flavours and tell us 
whether food is sweet, sour, bitter, or salty. Remember, all of 
the ice cream brands that Maya is testing are the same flavour:
vanilla. She is interested in other factors that affect how much 
people enjoy ice cream, not just the flavour. 

You may have heard that we “eat with our eyes first”. As weird as
that sounds, it’s true – if food LOOKS nice, we’re more likely to 
enjoy it. This is also true for smell. If you have a blocked nose, you’ll
 notice that food doesn’t taste as good. That’s because our sense of smell is an important part of our sense of taste.

All five of our senses work together, to give our brains as much information as possible about what we are about to eat.  We already know about sight, smell, and taste, but your other senses are involved too. Your ears might play a part – who doesn’t love the “pop!” of popcorn? – and your sense of touch is in charge of deciding what texture the food is. 
The signals our brain receives from our senses are all very important determining whether we like the food or not. So, to develop the best ice cream possible, Maya knows that every single sense has to be satisfied. 
That means that perhaps the most important part of ice cream testing is eating it!  
There is also a drawing alongside it of a boy with a blue shirt and yellow hair, licking an ice cream covered in sprinkles.

It’s not enough for Maya to try all the ice creams herself – for one thing, she’d get very bored of vanilla ice cream by the end! To get meaningful results, she needed a more scientific approach.

Dr Maya Warren in her lab, ready to test some ice cream. There are two chemistry beakers on the desk in front of her and she is holding a clipboard.

Maya used a special kind of test, which measures the sensory attributes of food. She recruited 17 people to take the test, and each person had about 20 hours of training beforehand to make sure they were able to explain their responses clearly. Serious stuff!

The testers had to describe six properties of the ice cream they ate:

  • how fast it melted in their mouth
  • how much force they had to use to break up the ice cream in their mouth
  • the size of ice crystals in the ice cream
  • how dense it was
  • how greasy it was
  • its overall creaminess

They measured each of these properties with a different test. For most tests, the tester put a small cube of ice cream in their mouth, and then gave it a score based on the property they were assessing. The score ranged from 1 to 10. So, for example, if a tester was scoring “creaminess”, a score of 1 would be very icy, whereas a score of 10 would be incredibly smooth and creamy.  

Maya worked hard to make sure that all of the ice cream tasting trials were fair tests. All the ice cream was vanilla-flavoured, bought at the same time, cut into cubes of the same size, and kept frozen at the same temperature. Maya kept track of what brand each one was by giving them random 3-digit numbers, which only she knew. That meant that the testers had no idea what brand each ice cream was, so they couldn’t be biased.

Four cubes of ice cream, numbered 680, 123, 327, and 945. Each cube is the same size and looks very similar to the other cubes.

Each tester also tasted the same kind of ice cream multiple times, to allow Maya to assess the reliability of their responses. By repeating each taste test, Maya could see if the testers reported the same score for a particular type of ice cream over multiple trials. If they did, she could be reasonably sure that the results were reliable.  

There was a large amount of variation in properties across all the tested ice creams. There are a lot of reasons why this could be, from the different types of freezer different brands used, to the way the ice cream was churned, or the quality of milk. These were factors which Maya had not been able to control, that were likely to have had an impact on the final product.

With all her results gathered, Maya was able to rank all eighteen of the ice-cream brands. She could order them by fat content, or by time taken to freeze, or even by how greasy the ice cream tasted. Whichever way she ranked them; different ice creams came out on top each time. For each aspect of ice cream, a different ice cream brand was the ‘best’.

Maya supposed that this was a good thing – we all have a favourite ice cream after all, and it’d be a shame if they were all the same.

Maya may have not been able to find an ‘overall best ice cream’, but what she had found instead was that the complicated science of ice cream making has given us an amazing variety of ice cream. All of the ice cream products she studied were unique, and each had different advantages!

And while there may be an ice cream out there for everyone, Maya knows the properties she prefers: creamy, smooth, and delicious. This research earned her a doctorate in food science, and after all that work, she definitely deserves a frozen treat!

Dr Maya Warren at her graduation. She is wearing a black graduation robe and cap with a pink tassel. In one hand, she is holding her rolled diploma; in the other hand, she is holding an ice cream.

Now, Maya works as the Head of Research and Development (also known as “Tastemaster”!) at Cold Stone Creamery, an American chain of ice cream stores. That means that she is paid to create and eat ice creams – what an amazing job!

More importantly, Maya gets to use her scientific training every day to create the best ice cream possible. She designs new flavours, creates recipes, and works hard to come up with exciting ice cream ideas that use the best quality ingredients she can find.

Maya’s love for ice cream also takes her all over the world! She’s tried tea-flavoured ice cream in Taiwan, ketchup-flavoured ice cream in Canada, and even chicken and waffle-flavoured ice cream in her home state, Missouri. Maya’s company send her to lots of different countries because they want her to experience the ice cream culture there and bring back inspiring ideas.

A drawing of ice cream tubs as you would find them in an ice cream cafe. Across the top there are five tubs: oreo, which is white with brown speckles; vanilla, which is yellow; garlic, which is white; strawberry, which is pink, and caramel, which is light brown. Along the bottom, there are five more tubs: ketchup, which is pink with red splotches; octopus, which is blue; tea, which is green; chicken and waffles, which is orange, and chocolate, which is brown.

While Maya admits her job may have some low points – like the time she had to try garlic ice cream – she can’t think of anything she’d rather do. She’s taken her life-long loves of ice cream and chemistry, and found a career where she gets to think about both every single day!

So next time you eat an ice cream, think about Maya, and how much science has gone into your scoop.

Thank you for reading!

This story was written as part of a Masters in Science Communication project, investigating whether storytelling is an effective way to teach children about science and scientists. As a result, I would really appreciate some feedback, which you can give by answering a short survey. The survey takes less than 5 minutes to complete, and I will use the results to develop even better science stories in the future. To help, just click on the button below.

A text box. It reads: 
Glossary
aerated – something is ‘aerated’ when a gas has been circulated through it. You can tell that foods like ice cream and mousse are aerated, because of their light and fluffy texture.
biased – when something or someone is biased, the information they give could be misleading or incorrect. An example of bias here would be, that if one of the tasters worked for an ice cream brand that was being tested, they might say that it was the best one in all of the tests, even if it wasn’t. This would affect Maya’s results.
churn – to shake or mix something vigorously. 
consistency – the way in which something holds together. This word is used to describe something’s texture or thickness.
control (variable) – things that we need to ensure remain constant. If they were changed, they could have an effect on the results. This would make it harder for the researcher to see the effects of the variable being tested. 
culture – behaviour or items shared by a group of people, such as a society. Food is often a key part of a country’s culture.
data – a collection of facts, such as numbers, measurements, observations, or words.
density – a measurement that takes into account both weight and volume. Denser objects weight more than less dense objects, even if they are packed into a space of the same size. 
doctorate – the highest degree that is given by a university. People who obtain doctorates can call themselves “Dr”.
factor – something that has an effect on an experiment. 
fair test - a test where only one thing (also known as a factor, or variable) is changed at a time. By only changing one thing at a time, the researcher can be certain that the thing changing is what has caused the results of the experiment.
freezing point – the temperature at which a liquid freezes into a solid.
gas – matter that has no defined shape, and is made of particles which are not packed in a set structure.
liquid – matter that will take the shape of its container, and is made of loosely packed particles.
manufactured – produced on a large scale, using machinery.
mixture – a substance made by mixing other substances together.
particle – a tiny amount of matter.
process – a series of actions or steps taken in order to achieve a particular goal.
property – any measurable trait that you can use to describe matter e.g. density, colour, mass, volume, length, hardness, temperature…
quality – a measure of excellence. Something that is of high quality is good compared to other things of the same kind. 
quantity – an amount or number of something.
rank – a place in a grading system. For example, if you come 3rd in a running race, you are ranked 3rd best of the runners. 
reliability – if results are reliable, they are consistent and trust-worthy.
richness – food is ‘rich’ if it contains lots of butter, oil, eggs, or cream. This makes the food thick and creamy.
sensory attributes – aspects of food that can be detected by the human senses e.g. appearance, smell, flavour, taste, and texture.
solid – matter that retains its shape, and is made up of tightly packed particles.
states of matter – matter is anything that takes up space. There are three states of matter – solid, liquid, and gas.
substance – a physical thing that can be seen, touched, and measured.
taste buds – small nerve endings on the tongue and in the mouth, which provide the sense of taste. 
texture – the feel, appearance, or consistency of a substance. It describes properties that can be detected by the sense of touch.
transformed – when something is transformed, there has been a major change in its shape, nature, or appearance.
variation – differences in results. 
volume – the amount of space that something takes up.
A text box. It reads: 
Hungry for more? 
If you’ve loved hearing about how Maya used her love for chemistry to find a career in ice cream, have a think about these questions…
1.	Test your learning! Fill in the blanks using the words below, to create a short summary about Maya.
Dr Maya Warren is a food scientist. She looks at the ___________ of food, and works out how the ingredients affect a food’s ________________. Maya’s favourite food is ice cream, and that’s what she studies every day! One of her favourite things about ice cream, is that its ingredients come from three different __________ of _________. It’s made of _______, a liquid; water that is ___________ into ice; air, a ________ that is pumped through the ice cream mixture, and _________ sugar syrup. The way that these ingredients are combined gives ice cream its unique _________________. Ice cream is soft, fluffy, and creamy! Maya loves to try ice cream from all over the world, including ketchup ice cream from _________ and amazing ______ ice cream from Taiwan! What a job!

Canada             properties              states              texture       liquid                                  
gas          chemistry        frozen        cream        matter     tea

2.	You’ve heard all about Maya’s experiment, but what about trying one of your own? With help from an adult, or as a class, try out this activity from Scientific American – you’ll have tonnes of frozen fun! https://www.scientificamerican.com/article/scrumptious-science-making-ice-cream-in-a-bag/

3.	Maya’s friend Simon loves ice cream almost as much as she does, but he can’t get his head around any of the confusing chemistry! Can you make a poster for Simon, that shows what the differences between solids, liquids, and gases are? Use the box from the story to help you out, and make sure there are some nice clear drawings for Simon to learn from!

4.	Throughout her experiment, Maya worked hard to make sure that each test was fair. Can you explain how she did this? What factors did she change each time? What factors did she keep the same? Remember to think about why she did these things, as well as how!

5.	Maya used a specially designed taste test to compare the properties of different ice creams. Why don’t you try to design a taste test of your own! It could be to compare different kinds of fruits, different chocolate bars, or even different chicken nuggets – but it needs to focus on the properties of the food, and how you could measure the differences between different kinds.

Resources

Maya’s research paper: Warren, M., Hartel, R. (2014). Structural, compositional, and sensorial properties of United States commercial ice cream products. Journal of Food Science. 79 (10): E2005-E2013.

More information about ice cream and how it’s made:

Video: Watch ice cream being made!

Article: The science behind ice cream

Video: Make your own ice cream (follows the same method as the Scientific American activity above)

More information about Maya and food science:

Maya’s website

Article: An interview with Maya

Video: Food Chemistry

Video: Where does our food come from?

More information about states of matter:

Video: What are states of matter?

Test your states of matter knowledge with this quiz!

More information about material properties:

Article: Properties of materials

Games, Resources, and Lessons

Acknowledgements

Maya did not produce this research alone; she was supported by Dr Richard Hartel. He too deserves credit for this discovery – good science is often best done as a team.  

This story would not be nearly so good without its illustrations by the wonderful Sofya Tamarina, and the advice and support of Dr. Nicola Hemmings.

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