Learn the science behind:
Granita: you can’t scoop it into a nice ball. And it’s a little watery, slushy even. But, this refreshing, versatile treat is a hot weather mainstay that features prominently in many delicious desserts around the world.
Making light and flaky granita ice is easier when you understand the science behind this frozen dessert. By regularly scraping the mixture as it freezes, you can prevent your granita from forming well-organized ice crystals and achieve that perfect melt-in-your-mouth texture.
Crystallizing water into ice
Key to making just about any frozen dessert is properly managing the process by which you transform your liquid into a frozen solid: ice! Once the cold, frozen treat enters your mouth, it melts—a refreshing sensation. This simple phase transition between liquid and solid lies at the basis of many desserts. And making a flaky granita is all about controlling that phase transition.
Converting water alone into ice doesn’t make for very good ice cream. Ice cubes are useful for cooling a drink, but not very yummy to snack on. You need something else to make good ice cream.
Granita is one of the simplest ice cream styles out there. It melts in your mouth for a very pleasant eating experience because of two principles that you use to control and change the way ice crystallizes:
- By adding sugar, you prevent all water from freezing.
- By stirring the mix regularly, you break up crystals and ensure you get a flaky texture.
So let’s see how and why that works.
Granita is sugar and water
Most granita recipes call for sugar and fruit juice (fruit juice itself is essentially water and sugar). This flavor may come from the fruit juice, an additional ingredient, or a flavored drink such as coffee. Some recipes also call for a type of liquor.
So, in short, we have: water + sugar + flavor + alcohol (ethanol). The flavor is just there for taste, it doesn’t truly impact the texture of the granita. Therefore, it’s all about the sugar, water, and alcohol.
Sugar lowers the freezing point of water
When making ice cream, you’re playing with the concept of freezing point depression. This is when the freezing point of a liquid (water in our case) is lowered due to an ingredient that’s dissolved within that water.
Sugar molecules dissolved in water interfere with the water molecules when they try to form solid ice crystals; this makes it harder for ice crystals to form. As a result, they only start to crystallize into ice at lower temperatures.
By adding sugar, you’re ensuring that not all the water will freeze – instead, while some water molecules will freeze and form ice crystals, others may remain in a liquid state. This ensures that a granita doesn’t turn rock solid immediately.
And alcohol can do the same
If your granita also calls for some sort of liquor, the recipe is taking advantage of alcohol’s properties to lower the freezing point of water. Alcohol, or ethanol to be more specific, is even better than sugar at lowering the freezing point: any amount of alcohol will lower a mixture’s freezing point more than an equal weight of sugar.
As such, if your granita recipe calls for liquor, and you don’t want to use it, be sure to correct for it by adding extra sugar. That way, the sugar can compensate for the missing power of the alcohol.
Scraping granita breaks crystals
A good granita contains lots of large, visible ice crystals. This is quite different from many other ice creams where you actually do not want to see any ice crystals. A perfect granita is characterized by slightly chunky crystals, instead.
To get these flaky crystals, it is crucial that you stir and scrape the granita regularly while it is freezing. As your granita freezes, liquid water starts to transition to solid ice crystals. Not all crystals form simultaneously—this takes time (and elbow grease)!
It takes energy for an ice crystal to form, but it takes less energy for it to grow. If you left your granita undisturbed, it would only form a few very large crystals. But, by scraping the granita regularly, you’re helping to make sure these crystals break down, remaining small, soft, and delicious!
Scraping a granita is, in a way, very similar to churning ice cream. When you’re churning, you’re breaking down crystals all the time; however, in an ice cream machine, you can keep those crystals a lot smaller in size than you could by manually scraping the ice cream. For a semifreddo, we don’t scrape, nor churn, but we use eggs and fat to create a nice texture.
Lack of fat keeps it slushy
A granita is very simple and only uses a few ingredients. Adding other common ice cream ingredients like cream or other fats would change your granita quite a bit. Most fats turn solid well above the freezing point of water, a process which will severely impact the texture of your granita. These fats will interfere with the crystal forming process, and as a result, you might not be able to get those large flaky crystals!
Granita is a great way to see these scientific concepts in action. Try changing the amounts of sugar and/or alcohol in your recipe to better understand how these ingredients impact a granita’s texture. And enjoy experimenting with different flavors—since granitas don’t contain any fats, their flavor tends to be very bright and vibrant. Granita is a great first step into the ice cream making arena—go forth and conquer!
Whitney Filloon, Shave Ice, Explained, May 24-2018, link