There is no competition for my favorite ice cream flavor. It is undoubtedly chocolate chip cookie dough. This is a grown up ice cream, though, because I included a little bit of alcohol. Not too much of course. In fact, I didn’t add the alcohol for flavor, but instead for texture.
I decide to experiment with freezing point depression by utilizing a bit of alcohol. Using estimations, the van’t Hoff equation, and a few pieces of paper, I determined that to get the optimal freezing point depression ½ a cup of sugar and 3 tablespoons of vodka were needed with a little assistance from salt. I won’t bore you with the details of how this was derived, but I can explain some theory.
Every pure liquid has a temperature at which it will freeze. However, most liquids found in nature are not pure and contain some solutes. These solutes interfere with the formation of ice crystals, so that to properly freeze the liquid must be held at colder temperatures than usual. It is not the mass of the solutes that effect the freezing point depression, but the amount of molecules.
In most ice creams, sugar is used to lower the freezing point. Freezing point depression creates a smoother and creamier product, when done in the right amount. If overdone, you will have ice cream that contains traces of liquid that is unable to freeze. What if you don’t want overly sweet ice cream? In that case, it is possible to use salt or alcohol to lower the freezing point. Because of their smaller molecular size, they are able to lower the temperature in much smaller mass quantities than sugar. The one drawback to using these solutes is that the ice cream will melt slightly faster than if only sugar is used.
1.5 cups of heavy cream
1.5 cups of whole milk
1 tablespoon of vanilla
Pinch of salt
6 whole eggs
½ cup of sugar
3 tablespoons of Irish Cream
- Bring cream, milk, and salt just to simmer in heavy medium saucepan over medium heat. Remove from heat.
- Whisk eggs and sugar in large bowl to blend.
- Temper the custard into egg mixture: While whisking, slowly pour cream into egg mixture adding a little at a time until about one third of the cream is incorporated into the eggs. Then stir the egg mixture into the pot with the rest of the cream.
- Add vanilla to custard then turn the stove top to medium low. While constantly stirring, bring the cream/egg mixture to about 170°F or until mixture thickly coats the back of a spoon.
- Remove immediately from stove and strain the mixture into a medium bowl. Then stir the Irish cream into the custard base.
- Allow the custard to cool to near room temperature (about 30 minutes) then place bowl in refrigerator for at least 3 hours (overnight preferred).
- Follow the directions on the ice cream freezer to form ice cream.
- Pour the ice cream into a medium sized bowl. Then fold in the cookie dough.
- Freeze ice cream until it is solid (about 1 hour).
Cookie Dough Recipe
1 stick unsalted butter softened
3/4 cups packed brown sugar
1 teaspoons vanilla
1/2 teaspoon salt
1 cup all-purpose flour
2 tablespoons milk
1 cup of chocolate chips
- Cream the butter and sugar together.
- Then stir in vanilla and salt. Stir in flour. Then stir in milk.
- Finally, stir in the chocolate chips.