Churning is the process by which the liquid ice cream base is mixed vigorously inside the ‘churn’ of an ice cream machine.
The churn is a bowl with insulated walls that is frozen prior to the ice cream base being added.
It also has paddles that agitate and stir the ice cream while it cools. This allows for an even texture and consistency to your ice cream.
The churning process incorporates air into the ice cream, boosting the volume. The more air incorporated into the ice cream, the faster the ice cream will melt.
The additional volume generated during churning is known in the industry as overrun. Cheaper ice cream has more overrun, meaning it weighs less and will melt faster.
At the same time, churning helps the water contained within the ice cream base form many tiny ice crystals through a process known as propagation.
The smaller and more regular these ice crystals are, the smoother and creamier the texture of the ice cream will be. This is done through constant and consistent churning.
This perpetual motion means that the crystals do not have as much time to clump together and form chunks of ice that would disrupt the texture.
So what can happen if you over churn your ice cream?
The most likely occurrence is that your ice cream will become icy and grainy.
This is because people believe that the churning process will completely set their ice cream. This is simply not how ice cream works.
It may develop large fat globules and leave a waxy film on the interior of your mouth. This happens because fat particles clump together as the mixture churns.
If it is allowed to churn excessively, too much of this clumping happens in a process known as fat de-stabilization (also called partial coalescence).
If you continue churning, your ice cream may also turn to something that resembles butter. This is because the continued fat de-stabilization will increase the solidity of your ice cream.
Some people may mistake this for their ice cream freezing, however, this is not the case. As milk eventually turns to butter with repeated churning, so will your ice cream base.
How to Tell Ice Cream Has Finished Churning
You should allow it to churn in the ice cream machine until you can run a path through it with your finger. If this path remains without filling in, your ice cream is ready to transfer to the freezer to set.
Another good indication that your ice cream has churned correctly is when it has the consistency of soft serve and begins to pull away from the sides of the churn.
Melting It Down
One way to fix over churned ice cream is to allow it to melt completely. You can then re-churn the liquid ice cream.
It will not become as hard and thick as ice cream that has been churned once. Instead, it will become more similar in texture to soft-serve ice cream, but it will still work.
Changing the Recipe for Your Base
There are many reasons why ice cream does not set or churn properly, and many times your recipe is to blame.
Check your sugar to milk to heavy cream ratios and experiment with different quantities.
Check Your Ice Cream Machine More Often
A good way to prevent your ice cream from over churning is to check on the churning process periodically. Churning tends to take around 30 to 35 minutes in most ice cream machines.
We recommend setting a timer for 10 minute intervals and checking on your ice cream at each of these.
It will not be firm, instead, it should have the consistency of soft serve. At this point, you should know that it is ready to be transferred to the freezer to set firm.
It is particularly important to pay close attention once the ice cream churning process has passed the 25 minute mark, as this is the boundary where over churning is most likely to begin.
Check the Churning Speed of Your Machine
If your churner is agitating the ice cream base too slowly, you can develop ice crystals inside.
The faster the churning speed, the more creamy your finished ice cream will turn out.
Check the Emulsification of Your Ice Cream Base
Improperly emulsified bases can cause the fat globules to clump together too much, resulting in a buttery product.
To fix this, try to blend your warm base liquid with an immersion blender before you add it to your churn. Leave it in the refrigerator overnight to age.
We recommend giving the base a second blend before adding to the churn to decrease the risks of over- or improper churning.
Try Adding a Stabilizer
Common stabilizers for ice cream include glucose, carrageenan, xanthan gum, corn syrup, and guar gum.
These are added to help in the emulsification process during ice cream making. They help to combine the fat, sugar, protein, and water and hold them together in a stable solution.
The stabilizer will also stop the ice cream melting as soon as it is removed from the freezer, and prevent it from refreezing too rapidly and forming ice crystals.
Additionally, stabilizers will help your ice cream store better in the freezer.
Try Adding an Alcohol
Adding alcohol will lower the freezing point of your ice cream.
By adding alcohol to your base mix, it will make it harder for ice crystals to form. This will also reduce the likelihood of your ice cream over churning.
Add alcohol in a ratio of roughly 3 tablespoons spirit per quart of ice cream base. Vodka is a neutral option, but others work too.
Freeze It in Small Portions
If your ice cream is teetering on the verge of being over churned, freezing it in individual serving portions will help.
This means that it will not be taken in and out of the freezer repeatedly. It will not be allowed to thaw and refreeze, which is what causes ice crystals to form.