Semifreddo Science: Using The Power of Eggs to Make This Airy Dessert

Semifreddo, a frozen light, and airy dessert is a great example of using the power of eggs and cream to hold onto air. With just three simple ingredients: eggs, sugar and cream, you can make a delightful dessert.

But having trouble making a semifreddo? We’ll give you a better understanding of what makes the cream and eggs fail and succeed at their jobs. Hint: never heat the cream, nor curdle the eggs!

Air makes a semifreddo less cold

Semifreddo is an, originally Italian, frozen dessert, that isn’t as cold as you might expect it to be. It’s also surprisingly light compared to ‘regular’, scoopable ice cream. Why? Because of the large amount of air that’s incorporated into a semifreddo. If you’d had a closer look at a semifreddo, it looks more like a frozen mousse than an ice cream. These air bubbles set a semifreddo apart.

First of, air bubbles can serve as an insulator. If an ice crystal touches your tongue, it will immediately give a cold sensation. However, if the ice crystal doesn’t directly touch your tongue, but is separated from your tongue by a layer of air, it won’t feel as cold. This is what all those air bubbles in a semifreddo do. They ensure you don’t just touch ice crystals directly, but also a lot of insulating air bubbles.

Semifreddos aren’t the only ice cream style that contain air. A lot of ice creams do, and we’ve gone through the role of air in ice cream in general more extensively here.

And makes it softer

Apart from making a semifreddo feel warmer than it is, air also impacts the texture of a semifreddo. The air bubbles make it lighter in consistency. As a result, it is easier to bite through and cut into smaller pieces. Just try ‘cutting’ through air, that’s very easy. But cutting in a solid piece of ice is very hard. Cutting through ice with air bubbles is harder than cutting through pure air, but a lot easier than cutting through pure ice!

Making a semifreddo = incorporating air

The most crucial part of making a semifreddo is to incoporate all this air. As a result, the way to make ice cream is a little different than for more ‘standard’ ice creams. Instead of using an ice cream machine to aerate an ice cream base or stirring an ice cream every so often while freezing, we incorporate all of those air bubbles before we even start the freezing process.

To do so, we use two aeration powerhouses:

• Heavy cream &
• Eggs

To incorporate air into ice cream you need to: 1) make sure you can get the air in, 2) make sure that the air stays. This sounds obvious but it’s crucial to control them both!

Fats hold onto air in cream

If you whisk heavy cream for long enough it turns into a light and fluffy foam. However, this only works for high-fat creams, often referred to as heavy cream, and whipping cream. This is because you need the fat to hold onto that air.

Fat particles in cream don’t necessarily like to sit in water, they’re hydrophobic. When you whisk cream, those fat particles immediately take advantage of the situation. They’ll organize themselves around those newly incorporate air bubbles. This way, they don’t have to contact water as much anymore.

This bubble stabilization isn’t strong enough to keep whipped cream fluffy for days. However, when making semifreddo, you only need its power for a few hours at most.

Granitas generally don’t contain any fat, or very little, it’s why their texture is quite different, more flaky.

Eggs’ proteins get to work

What’s even better at holding onto air than cream? Eggs. Eggs contain a lot of proteins. Parts of these proteins prefer to sit in water, whereas other parts don’t like water as much. When air bubbles are whisked into eggs, the water-hating parts of the proteins grab their chance and will sit around those air bubbles, effectively locking them into place.

Egg proteins are even better at forming and stabilizing a foam if they’ve been heated. By gently and carefully heating eggs while whisking you’re helping the proteins to uncurl. This makes it easier for the proteins to organize themselves around those air bubbles! It’s a delicate process though. Overheating the eggs will cause them to curdle. You’ll find semifreddo recipes using just the egg yolks, just the egg whites, or whole eggs.

Semifreddo is related to Italian meringue!

To make a strong stable semifreddo, you’ll need to whisk egg (yolks) with some sugar while heating. This may sound familiar. It’s a technique that’s used to make Italian meringue as well. Italian meringue only uses egg whites, but the process is very similar.

Semifreddos can’t be stored for long

Unlike many other ice cream styles, semifreddo ice cream isn’t that stable. Even fully frozen, it’s best eaten within a week or so. Over time, the sides may dry out a little and the fats are more susceptible to oxidation.

References

Beatric Piselli, Quali sono le differenze tra parfait e semifreddo? Scopriamole insieme!, 2019, link

Italian gelato, Semifreddo, link