If you’re like me, you crave homemade sorbets and ice creams in the spring and summer, but you don’t have a beloved ice cream maker to do the job for you. It’s kind of devastating when I scroll to the bottom of a delicious ice cream recipe and it reads “churn according to manufacturer’s instructions.” But why is it necessary for ice creams and sorbets to be churned?
When temperature drops, water molecules move more slowly. If the temperature drops low enough, water molecules will be so stagnant that the water will turn to a solid. In other words, the water begins to freeze as temperature drops below the freezing point. The ice crystals, upon forming, will want to grow as long as liquid water surrounds the ice crystal. When ice crystals are really big, a coarse and extremely hard texture is created. If you’ve ever tried making an ice cream or a sorbet by freezing some cream or some sugared fruit juice, you’ll know what I’m talking about. Hard as a rock.
So how do we keep the ice crystals from growing? Freezing foods quickly usually ensures a small enough crystal formation—encouraging crystal foundation faster than crystal growth. In this case, however, more needs to be done in order to have a scoop-able ice cream!
The main approach here is to get in between the water molecules and prevent them from interacting with each other. This keeps the growth rate low. There are three ingredients that can easily accomplish this.
Sugar: sugar binds water and thus keeps it from interacting with other nearby water. Too much sugar, however, and the ice formation is actually impeded. This can cause incomplete freezing or even an ice cream or sorbet that melts extremely quickly. An optimum sugar amount that won’t cause adverse freezing effects alone is not enough to prevent large crystal growth, so the other two ingredients need to be employed.
Fat: fat physically blocks water molecules from interacting. As I’m sure you’re aware, water and fat do not get along, so water will not try to play with fat to get to other water molecules if it’s not easy. Because of the ice cream mix structure and slow-moving water molecules at lower temperatures, it makes it difficult for water to get around the fat.
Air: This is where the ice cream machine comes in. Air physically impedes crystal growth just like fat and is incorporated during churning. You may have heard of this being called the overrun. It is this process that we want to mimic in our homemade ice cream or sorbet.
Sarah over at The Vanilla Bean Blog has been able to put together some excellent no-churn ice creams because of a high fat content and a whipped cream component. In our case, however, we’re making a sorbet. So there isn’t much fat to work with. We’re stuck with sugar and air being the workhorses here. In order to incorporate air into the sorbet, you have to whip the mix while it slowly freezes in your freezer. It results in a texture a bit like a granita, so it’s a great solution! Make sure before you make this that you have several hours to devote to this. You’ll have to whip every hour until solid. Enjoy! Preferably lounging outside with your favorite sunnies.
Blueberry Basil Lemon Sorbet
Technique from Apples for Jam
Makes about 3 cups
6 ounces blueberries (a little over a cup)
1 ½ lemons
A pinch Kosher salt
8 leaves basil
About 5 one inch slices of lemon zest, no pith
1 cup sugar
1 ½ cups water
⅓ cup milk
1. Puree the blueberries, the juice from one half of a lemon, salt, and basil together. Work quickly as the mixture will begin to brown as it is exposed to air.
2. Put the sugar, juice from the remaining lemon, lemon zest, and water together in a large pan. Bring to a boil and cook for about five minutes—allowing the sugar to dissolve.
3. Remove the lemon peel and allow the sugar syrup to cool for about 10 minutes. Add to the puree and mix. Add the milk and mix well. Refrigerate the mix until it has cooled.
4. Strain the mix into a second container getting rid of most of the blueberry and basil solids. Give the mix a brisk whisk either by hand or with a hand mixer. This is the first air incorporation step. Put the mix in the freezer.
5. Every hour, take the mix out of the freezer and give it a brisk whisk. The ice will likely begin to form around the outside first, so make sure to scrape the outside well when whisking. When it looks like the sorbet is nearly firm, give it one last whisk and let it finish setting up in the freezer before serving. (Alternatively, use an ice cream machine and churn according to manufacturer’s instructions)