Guide
Why ice cream turns icy, and how to stop it
Icy ice cream is the most common disappointment in home churning, and it nearly always comes down to one thing: water that was allowed to freeze into crystals big enough to feel on your tongue.
The short answer
Every ice cream contains water, and that water will freeze. The goal is millions of crystals too small to notice rather than a few big ones you can feel. Crystals stay small when the mixture is cold before it churns, freezes quickly, is kept moving while it freezes, and holds enough sugar and fat to get in the way.
What is actually happening
Ice cream is mostly water, however rich it tastes. As it freezes, water molecules join onto whatever ice is already there. Freeze slowly and you get a few large crystals, which is what “icy” means in the mouth. Freeze quickly, while stirring, and you get a vast number of tiny ones, which read as smooth.
Everything below is a different way of keeping those crystals small.
Cause 1: there is simply too much water
Fruit is the usual culprit. Strawberries are around 90% water, and stirring raw fruit into a base is an efficient way of adding ice to it.
Cook fruit down first, or roast it. You lose some volume and gain concentrated flavour and far less water. The same applies to anything wet: brewed coffee, fruit juice, a splash of milk to “loosen” the mixture.
The roasted strawberry recipe exists mostly to make this point.
Cause 2: the base was not cold enough
A machine can only freeze so fast. Put a base in at room temperature and the machine spends its energy cooling it down rather than freezing it, so the freezing happens slowly, and slow means big crystals.
Chill the base for at least four hours, ideally overnight. It should be properly fridge-cold, not merely cool. If you are in a hurry, sit the bowl in iced water and stir.
- Freeze a freezer-bowl machine for a full 24 hours, not the four the box claims.
- Chill the storage tub as well, so the ice cream is not partly melted as you pack it.
Cause 3: not enough sugar or fat
Sugar lowers the freezing point and physically blocks crystals from joining up. Fat coats them and softens the texture. Cut either one and you are making a sorbet by accident.
This is why “healthy” ice cream recipes so often disappoint: the things being removed are the things that make it smooth.
- A litre of ice cream base wants roughly 130–170 g of sugar.
- A tablespoon of vodka, or swapping a little sugar for honey or golden syrup, keeps things softer still.
- Full-fat dairy, every time. Low-fat milk makes ice, not ice cream.
Cause 4: it froze too slowly
- Use a shallow container, not a deep tub: the middle of a deep tub can take hours to freeze.
- Metal beats plastic, because it carries heat out faster.
- Do not overfill the machine. A bowl crammed to the brim churns sluggishly and freezes unevenly.
- If you are working without a machine, beat the mixture every 30 minutes while it freezes.
Cause 5: the freezer keeps warming up
Every time ice cream partly thaws and refreezes, the small crystals melt and reform as larger ones. A week of being left on the counter for five minutes a day will wreck a batch that started perfectly.
Keep it at the back of the freezer rather than in the door, press parchment onto the surface before lidding, and put it back promptly.
Frost on the surface of the ice cream is the tell-tale sign that it has thawed and refrozen.
Can an icy batch be saved?
Not really, but it can be repurposed, and nobody has to know. Let it soften, blitz it smooth in a food processor and refreeze: it will be better for a day or two. Or blend it into a milkshake, where iciness is invisible.
Then make the same recipe again with one thing changed. Nearly always it is the chilling time.
Put it into practice