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The Science of Ice Cream: How To Make It At Home
Photo Tao Wang

The Science of Ice Cream: How To Make It At Home

Learn how to make a mouth-watering ice cream without an ice cream maker, with few physics notions and some smart tips

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There aren’t many foods that are almost universally beloved by both children and adults. There is one, however, whose very name can evoke squeals of delight even at the end of the most lavish meal. Of course, we are talking about ice cream. But have you ever wondered why it’s so enthusiastically adored?

The answer lies most likely in its very simplicity: milk, water, sugar and the eventual addition of a natural flavor. Basic ingredients, sure, and yet they come together after a preparation that few attempt at home. Yet with a few little suggestions and some scientific insight, making ice cream is absolutely possible — even without the help of a fancy machine. Let’s take a closer look at the main star of our story.

Scientifically speaking, ice cream is a colloid — an emulsion: a substance dispersed in microscopic drops into another substance.
If we take a spoonful of water and we pour it into a bowl of oil, then beat it briskly with a fork, we have a good example of an emulsion. An emulsion, by definition, is composed of two substances that aren’t normally mixed together — like water and oil.

Ice cream fits this definition well: looking at it through a microscope, you can see small fat molecules suspended in a water and sugar solution (many in the shape of small ice crystals), often with the addition of many air bubbles. The fat content, obviously, comes from the milk—which is why it’s always better to use the full-fat version: it will ensure a compact and velvety consistency. For an even creamier ice cream, you can add another fat like cream or egg yolk. This, fundamentally, makes up the basis for ice cream.

Commercial ice creams usually add another stabilizer and emulsifier: the first guarantees that the emulsion remains well mixed and that the fat won’t separate from the water, while the emulsifier ensures that the fat molecules are spread out evenly. These aren’t needed if you’re making ice cream for immediate consumption, but there are some natural variations that will give your homemade recipe an extra special touch. Gelatin is a great stabilizer, and an egg white can be a perfect emulsifier.

With this information, you now know everything you need to make a mouth-watering ice cream without an ice cream maker, although if you do have one, you’ll probably need a lot less effort to make a delicious dessert. Whether you make it by hand or by machine, it will be your arm — not your mouth — that will notice the difference.

First, prepare the “base”: mix 600 ml of fresh whole milk with 300 grams of fresh cream and 250 grams of sugar. Add the flavor of choice, or a bit of vanilla.
Pour everything into a pot and heat until 85°C to pasteurize it, stirring continuously.
Then place the pot into a bucket full of ice, in order to chill it quickly.
Now you have two choices: if you have an ice cream maker, use it; if you don’t, it’s time to roll up your sleeves. In the first instance, put the mixture in the refrigerator and leave it there for three hours. Afterwards, put it into the ice cream machine and turn it on. In the second scenario, put the mixture in the freezer and remove it after 40 minutes, then stir it briskly for one minute with a wooden spoon and put it back in the freezer.
At this point, repeat these steps every half an hour at least three times.

If you’re punctual and quick with the spoon, you’ll get a creamy, velvety ice cream that will delight even the most demanding guests — of any age.

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