|Kerber's mocha chip in a chocolate cone|
While enjoying a 14% butterfat mocha chocolate chip ice cream in a chocolate cookie cone, I got into a discussion with my friends about the differences between ice cream, frozen custard and gelato. We all proposed our theories and shared our experiences. When I got home, I did a little research. There are a number of factors that contribute to the flavor, texture and mouthfeel of our favorite frozen creamy sweets. All forms of ice cream are basically a mixture of milk, cream, sugar, flavorings and sometimes egg yolks. These ingredients have a chemical reaction that makes ice cream what it is - smooth, creamy and uniform. American style, also known as Philadelphia style ice cream has no egg yolks, but it is churned at a relatively high speed which incorporates a lot of air into the final product and it is frozen at a lower temperature which makes the ice cream firm and scoopable. The butterfat content affects the richness of the final product, but too much butterfat can also mute the flavor. Gelato has egg yolks and a lower butterfat content, which allows more of the flavor to come through. It is churned more slowly to incorporate less air and it is also frozen to a slightly higher temperature, giving it a more creamy texture. Frozen custard is always made with egg yolks and has very little air incorporated, making it much more smooth and dense. Most high quality ice cream starts with a custard base, which is hot milk or cream added to whipped egg yolks, then cooked until it thickens. After doing all this research, I was inspired to make my own.
I've made ice cream many times using a standard, basic ice cream maker. It has a double-walled tub lined with material that freezes solid. The frozen tub fits onto an electric motor and a paddle attachment is placed in the middle. The ice cream base is poured into the frozen tub and the motor rotates the paddle, simultaneously churning and freezing the ice cream in about 20 minutes. The soft ice cream is then placed in the freezer for several hours to harden. There are special machines for gelato and frozen custard that churn at a much lower speed to incorporate less air. Perhaps one day I'll invest in a fancy ice cream maker. For now, the basic model will have to do. I had a container of strawberries in the freezer that I'd picked a month before so I stocked up on the rest of the ingredients and put my double-walled tub in the freezer.
HOMEMADE STRAWBERRY ICE CREAM
2 cups half & half
1 cup heavy cream
1/2 cup of white sugar
4 egg yolks
1 1/2 cups of strawberry puree
1 tsp of vanilla extract
The zest of one lemon
1 tbsp of corn starch
a pinch of salt
Having done this a number of times, I have tested many variations in fat content, ingredients and flavorings. I have tried all kinds of different proportions of milk and cream, even adding some 2% milk to see if I could get good results with less fat. It didn't work at all and my final product was full of ice crystals. Some recipes call for more heavy cream than milk, but I find that too fatty and the ice cream leaves a film on the roof of my mouth. I prefer the combination of half & half and heavy cream. Half & half is an equal mixture of whole milk and light cream that has somewhere between 10% and 12% butterfat. Adding the heavy cream, which has about 25% butterfat, adds the richness I like without adding too much butterfat.
For this recipe, white sugar is fine. But I have made brown sugar ice cream and it is very good, especially with the addition of vanilla bean an candied pecans. I also find the addition of lemon zest adds a pleasant tartness without adding the acid, which would cause the dairy to curdle.
Finally, I have a secret weapon which allows me to add less egg yolks. When I first started making ice cream, the recipes I found called for as many as 6 egg yolks. That's because egg yolks have lecithin in them, which is an emulsifier and keeps the ice cream base from separating. Picture a jar of vinaigrette and think about how the oil separates from the vinegar. When you add a teaspoon of mustard, the dressing stays emulsified. Egg yolks have the same effect, but too many egg yolks make the final product taste too eggy. The answer is corn starch, which also acts as an emulsifier, helping bind the fat molecules to the water molecules so the mixture stays together and doesn't get icy. I found a couple recipes in which the corn starch completely replaces the egg yolks, but I have not been brave enough to try it yet.
The preparation is pretty simple. I started by putting the strawberries in the food processor. When I first started making ice cream, my motto was the chunkier, the better. But whole frozen pieces of fruit are very unpleasant to eat. Unless they are dehydrated, the liquid in the fruit freezes in the ice cream and you end up with fruity little ice cubes that hurt your teeth when you try to eat them. Pureeing the fruit adds the flavor without the frozen bits. However, I didn't make the puree completely smooth as I like a few little shreads of fruit to be visible in the ice cream. I put the half & half and cream in a heavy saucepan over low heat and added the pinch of salt. In a bowl, I mixed the egg yolks, sugar, corn starch and lemon zest together and set it aside. When the cream was hot enough to form bubbles around the edges, I started tempering the egg yolks. This process involves slowly bringing the egg yolks up to temperature before cooking the custard base. If you just dumped the hot cream into the egg yolks, they would scramble. While whisking the egg yolk mixture, I added a slow drizzle of hot cream, a ladle at a time, until I had about a cup of cream incorporated. Then I poured the entire egg yolk mixture back into the pot, added the strawberry puree and returned the pot to low heat. Some folks prefer to add the fruit puree at the end so they can strain the custard after its cooked. You could do that if you like, I just chose to do it this way.
Take the custard off the heat and if it looks a little lumpy, that's OK, just strain it into a bowl. Put the bowl into a bigger bowl filled with ice and stir the custard until it cools down to room temperature. Cover the surface of the custard with plastic wrap and put it in the fridge for several hours. You want this mixture to be cold when you put it into your ice cream machine. I made my ice cream base early in the day and in the afternoon I churned it. After its churned, the ice cream needs a few hours to fully solidify in the freezer. It was still a little soft when I served it, but the flavor and texture were perfect. I do love making my own, but there are so many excellent ice cream shops out there to try and there's no such thing as too much ice cream. The quest continues!