Homemade eggless icecream – Science of corn starch custard

Not too long ago we had visitors over who don’t eat eggs. For a main course this isn’t a problem, there are plenty of things we can make without eggs. However, when it comes to dessert the eggless choices aren’t as prevalent. Therefore I experimented making homemade eggless ice cream which turned out so good it’s just as good as a lot of my egg containing ice creams.

The secret: using corn starch to thicken and stabilize the ice cream. Since this is a food & science site, we’ll be discussing corn starch in more sciency detail, but not after sharing the ice cream recipe.

Homemade eggless ice cream

The recipe I made is actually a chocolate ice cream, but feel free to leave out the chocolate and cocoa and substitute for vanilla bean or any other flavour.

Homemade eggless icecream - Science of corn starch custard
Author:
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Serves: >8 portions
Ingredients
  • 250ml milk
  • 250ml whipping cream
  • 30g corn starch
  • 100g sugar
  • 50g cocoa powder
  • 75g dark chocolate (or whichever type you prefer)
Instructions
  1. Dissolve the corn starch in some of the cold milk (approx 30-50 ml) until it forms a nice smooth paste.
  2. Bring the rest of the milk to the boil and take from the fire.
  3. Pour the milk on the cornstarch mixture while whisking to mix the two together.
  4. Add the sugar and place the mix back on the fire.
  5. Heat the liquid while continuously whisking (this is important). You will notice it'll start thickening quite a bit. Take it from the fire once it has the consistency of a custard, you should not have to boil it.
  6. Mix in the cream, cocoa powder and chocolate immediately. The heat will melt the chocolate and the chocolate and cream will cool down the mix.
  7. Leave to mix to cool to room temperature.
  8. If you have an ice cream machine, follow the instructions of the machine and churn the ice cream until the program is finished. Put the ice cream in an air tight container and freeze until needed.
  9. If you do not have an ice cream machine it will take a little more effort. Pour the mixture in a freezer proof container (be sure to have quite some space left in the container). Freeze the mixture for approx. 30 minutes and stir the mixture. Continu doing this until it looks like an ice cream and has frozen considerably. The stirring in between it required to bring in air and break up any possible large crystals.
  10. Enjoy!

Why use eggs in ice cream?

Ice cream can be made without eggs in a pretty easy way. Simply mix milk, cream and sugar (salt may be added as well) and place in an ice cream maker. The water in the milk and cream will freeze and the sugar will cause for a softer texture because of the freezing point depression. There is a chance though, that the mix will just taste like frozen cream here since there aren’t a lot of components that influence the texture.

However, for making a smoother, richer ice cream, eggs are very helpful. Three main ingredients of eggs play a role here (read more on eggs-basics):

  1. Fats: eggs contain quite a bit of fat (especially the egg yolks which are commonly used in ice cream). This makes the ice cream richer. Since egg contains slightly different fats from dairy, chances are they complement one another.
  2. Proteins: egg proteins play an essential role in egg’s functionality in a lot of dishes (think: meringues, cakes, …). For ice cream the proteins are always heated just enough for them to unfold and denature. This way they can form a complex network. This network can inhibit growing ice crystals from growing any larger.
  3. Lecithin: this is an emulsifier and is good at making a so-called emulsion of water and fat. This stabilizes the ice cream and makes it easier for water and fat to mix, often resulting in smaller bubbles of fat in the water.

SeriousEats did a great experiment testing out the influence of the number of eggs on the ice cream quality. The preferred number of eggs is very personal, but it was clear that eggs greatly influence the texture of ice cream.

Making a custard for ice cream

When using eggs in ice cream they should never be used raw and just thrown in. The fat and lecithin will do their job, but the protein will not create the network you want. Therefore, for making ice cream the eggs have to be heated to get the proteins to unfold. The process is very similar to that of making a normale custard actually!

Substituting eggs – for corn starch

When making the eggless ice cream I wanted to find another way to make the custard base. Since we still had some custard powder lying around I decided to give that a try. That actually worked out very well. Of course, I wasn’t the first one to discover this, apparently Jeni has been using this for quite a while already!

When looking a little closer at my custard powder box I noticed the main ingredients was actually corn starch. This is how I eventually ended up using the corn starch for eggless ice cream.

What is corn starch?

For those of you unfamiliar with the term let’s first zoom in on corn starch. Corn starch is made from corn. Corn itself exists for the most part of  water and yes, starch. Starch belongs to the group of carbohydrates and is a very large carbohydrate, made out of a long chain of sugar molecules. As you can see in the infographic on flour, starch is made out of two different types of molecules: amylose and amylopectin. These together make that starch can thicken water based sauces and mixes.

Flour also contains a lot of starch, therefore flour can also be used to thicken foods. An example of an application is using it to thicken a pie filling.

Using corn starch in homemade eggless ice cream

When it comes to using corn starch there is one very important trick to use. Adding powdery cornstarch to a pot of warm water directly is a very bad idea. The powder will quickly form clumps. This is caused by the fact that the starch soaks up the water quickly. However, this will form a pasty layer around the remaining powder. It is virtually impossible to remove these clumps again using a whisk!

Therefore, always dissolve corn starch in cold water first. Once it’s been dispersed properly and all clumps are gone, it can safely be added to warm water. This is also the method I mentioned in this ice cream recipe, unfortunately, I’ve experienced clumps of cornstarch in my ice cream several times, no need to throw it away, but it does decrease the quality…

Further learning

Good luck making your own eggless ice cream recipes! There are tons of variations possible, with different flavours but also different sugars, fats, etc.

Haven’t learned enough yet on the topic of starch? Learn more about carbohydrates to start with, and then read more about thickening with flour and dive into risotto, it might not seem related to ice cream, but it is!

Want to learn more about ice cream? Here’s a semifreddo recipe (which does use eggs). Also, you can learn more about the role of sugar in ice cream when learning about freezing point depression as well as phase diagrams for ice cream.

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