The importance of fat in ice cream

Fat is an essential component of ice cream. So if you were thinking of getting rid of it in your homemade scoops, stop right there. Nonfat ice cream does exist, but it's an abomination!

The fat in ice cream is called butterfat and is found in the milk and the cream. It contributes to ice cream in several important ways:

1. it provides a creamy texture and mouth-feel
2. it adds its own flavor
3. it absorbs and delivers other flavors
4. it makes the ice cream firmer
5. it slows melting by stabilizing the air bubbles

But the amount of butterfat varies tremendously across the different types of ice cream:

Around 20% butterfat is the upper limit.^[1] Beyond that, ice cream will start to have a greasy mouth-feel that leaves an unpleasantly fatty film in your mouth. And since fat is hard, your ice cream will also become too hard to scoop!

Butterfat and flavor

The butterfat contributes its own delicious rich, creamy flavor to ice cream. So higher fat ice creams will be richer and creamier with a long, lingering aftertaste. And lower fat ice creams will be lighter and cleaner with a much short lived aftertaste.

But the butterfat also has a strong influence on any other flavors in the ice cream. And this is because butterfat very good at absorbing and hanging on to other flavors!

So if you make a high fat, strawberry ice cream, you won't taste that strawberry flavor immediately, because the butterfat hangs onto the flavor and delivers it slowly. When it is delivered, it will be slightly subdued by the fat. But it will linger for a long time afterwards.

In contrast, in a low fat strawberry ice cream, the strawberry flavor is neither slowed nor subdued by the butterfat. So it's much more immediate and punchy. The strawberry flavor will taste brighter. But it will also fade faster.

It's a good idea to think carefully about the flavors in your ice cream, how you'd like to deliver them and how long you'd like them to hang around for. Because playing around with the fat content will allow you to control this and alter the flavor profile of your ice cream!

Butterfat and texture

Fat is hard. So it also gives ice cream a hardness. This is good for ensuring ice cream has a firm texture. But as mentioned already, too much fat will make your ice cream too hard to scoop.

Also, while ice melts at 32°F (0 °C), butterfat melts at around 90°F (32 °C), which is just below our body temperatures. This means that once our ice cream is served, while the ice will start to melt at room temperature, the butterfat won't melt until it's in our mouths.

What's the significance of that? Well, just as butter left out of the fridge will soften but still retain its shape, the un-melted butterfat in ice cream will help the ice cream keep its shape even as the ice melts.

But the butterfat also effects texture and slows melting in another way...

Butterfat and air

The air in ice cream is also really important. It contributes a lightness and softness and stops the ice cream turning into a solid block in the freezer. Without air, ice cream would be more like a frozen milk lolly or Popsicle.

While the ice cream is being churned, it's the blades of the rotating paddle (or dasher) that introduce air into the mixture, just like a whisk whips air into whipping cream.

And just like whipping cream, it's the fat globules that keep the air in a stable state. In fact, the science of whipping air into cream is exactly the same as whipping air into ice cream...

As well as adding air to the mixture, the rotating blades cause fat globules in the cream and milk to be thrown about. Sometimes they collide. And when they do, they start to stick to each other. Soon, they start forming long pearl like strings.

This process is essentially de-stabilizing the fat and water emulsion in the mixture and is called "partial coalescence".^[2] It is often aided my added emulsifiers.

But what's important here is that the long strings of fat globules create a kind of scaffolding that surrounds and supports the air bubbles. So it keeps the air bubbles in place, in the ice cream.

Just like whipped cream! And just as cream can be over-whipped, so can ice cream. When this happens, so much fat joins together that the strings of fat become detectable by the tongue as tiny soft lumps.

This is called "buttering".^[3] If your ice cream has a butterfat content above 18%, and it's been over churned or there are too many emulsifiers, then there's a good chance that buttering will occur. For more on buttering and how to avoid it, check my troubleshooting ice cream page.

Ultimately we want to achieve enough partial coalescence to stabilize the air bubbles in the ice cream, but not so much that the fat starts to butter and becomes detectable in the mouth.

Controlling the butterfat content of ice cream

If you want to vary the amount of butterfat content in your ice cream (and you will want to try this!), then you simply change the proportions of milk and cream in your recipe.

How you do it will depend on what type of milk or cream (or any other dairy product) you're using, as they all have different butterfat contents... 

I tend to use whole milk and heavy or light whipping cream, depending on what's available.

Here are some commonly used proportions and some notes on the sort of ice cream they'll produce. The butterfat content is calculated according to whole milk and heavy whipping cream...

Experimenting with different levels of butterfat is great fun and will help you learn a great deal about how ice cream works! Be careful though...

As we've already discussed, too much butterfat will give your ice cream a greasy mouth-feel that leaves an unpleasant, oily film in your mouth. It also increases the chance of "buttering" where small globules of fat become detectable by the tongue.

Too little butterfat will mean there aren't enough fat globules to form the strings that support the air bubbles. The ice cream will also have a thin, watery mouth-feel. And will probably be wet and coarse.

My ice cream calculator will give you an accurate butterfat percentage according to the amounts of milk and cream you use in your recipe. I'd advise that you stick between 4 and 20% for homemade ice creams.

Extra sources of fat

Just when you think you've got your head around all this, things get even more complicated! Because any other ingredients that we may add to our ice cream, may also be sources of fat!

Eggs, nuts and chocolate all contain their own fats. Not butterfat. But these other fats will make their own contributions to hardness and mouth-feel and they can throw our carefully balanced mixtures.

So we may need to accommodate them by reducing the butterfat in our base recipe. This will be the subject of another post though!

Wrapping up

Fat is a very important component of ice cream. I totally understand, that in these health conscious times people may want  to reduce (or even eliminate) the fat in their ice cream.

But while we can certainly reduce it slightly, as home cooks limited by domestic ice cream makers and the basic ingredients we find in supermarkets, we're simply unable to cut it out entirely when we're making ice cream at home.

And to be honest, we really shouldn't want to. The fat content in ice cream is not a big issue unless you're eating gallons and gallons of it!

Rather we should be making the best tasting ice cream we possibly can and enjoying it in moderation. And because fat makes ice cream taste great, I certainly won't be cutting it out of my recipes anytime soon!

Check out my ice cream science page for more information of the scientific aspects of ice cream. Not only is it really interesting, it will also help you fix problems and make better ice creams!

References:

1. Cree D. (2017), Hello, My Name is Ice Cream. Clarkson Potter.

2. Goff H. D, Hartel R. W. (2013), Ice Cream. Seventh Edition. New York Springer.

3. Clarke C. (2004), The Science of Ice Cream. Royal Society of Chemistry.