After "what's your favorite ice cream?", the question I get asked the most as an ice cream maker is "what makes gelato different from ice cream?" How does gelato get that soft, elastic texture and slow-to-melt milkiness compared to ice cream's richer, creamier body?
It comes down to three factors: fat, air, and serving temperature. The more complicated answer? Things aren't always clear cut: this is food, not phylogeny, so individual recipes can blur the lines between the two. But there are some basic differences to keep in mind.
How Ice Cream Works
All ice cream is mostly water, and as water freezes, it forms hard, crunchy ice crystals. Besides great flavor, the ultimate goal of ice cream making is to keep those crystals as small as possible through added ingredients and technique. Here's how ice cream makers fight crystallization:
- Emulsifying fat into a base (or using already emulsified ingredients, like cream and milk) sticks fat molecules in between water molecules, literally getting in the way of ice as it freezes.
- Sugar also forms a physical barrier to crystallization, just like fat. When dissolved in water, it forms a syrup with a lower freezing point than plain water, and the sweeter a syrup is (i.e. the higher the concentration of sugar), the lower the freezing point becomes. As water starts to freeze in a syrup, the unfrozen water becomes, in effect, a more concentrated syrup. This process continues until you have a bunch of small ice crystals in a sea of syrup so concentrated that it'll never really freeze.
- Air is incorporated into ice cream during the churning process. Just like a light, fluffy angel food cake is easier to cut into than a dense fruit cake, a more aerated ice cream is easier to scoop, and has a fluffier, less dense texture.
- The temperature ice cream is stored at also has an obvious effect: colder ice creams are harder and more solid, while warmer ones are softer, with a looser texture.
There are some other tricks to keep ice cream soft, such as alcohol, starch, protein (in egg and milk), and natural stabilizers like guar gum and carageenan, but the top four above are the big factors at play.
Ice Cream vs. Gelato
Compared to today's American-style ice cream (that's one made with egg yolks, as is basically the new standard in home recipes and commercial products), gelato has less fat in the base and less air churned into it during the freezing process. American ice creams are heavy on the cream, and have a fat content, by American labeling law, of at least 10% (considerably higher in most homemade and many premium versions). Gelato, by comparison, uses more milk than cream, so it doesn't have nearly as much fat. Additionally, it usually—but not always—uses fewer (to the point of none) egg yolks, another source of fat in custard-based ice creams.
American-style ice creams are churned fast and hard to whip in plenty of air (called overrun), which is aided by the high proportion of cream in the base. The most high-end ice creams have an overrun of 25% or so, which means they've increased in volume by 25%; cheaper commercial versions can run from 50% to over 90%, which gives them a light, thin, fast-melting texture that isn't very flavorful (those bites are a quarter to a half air!). Gelato is churned at a much slower speed, which introduces less air into the base—think whipping cream by hand instead of with a stand mixer. That's why it tastes more dense than ice cream—it is.
And what about sugar? Well, sugar levels vary wildly in ice cream and gelato recipes, so there's less of a hard difference there.
If you make ice cream at home, you may be wondering about your ice cream machine: does it churn at ice cream speed or gelato speed? The truth is, most of the consumer models on the market churn at about the same speed, none of which are as fast as the commercial machines used to make American-style ice cream. But you can make both ice cream and gelato in your machine—remember, air is only one of the differences between them.
All these differences give gelato a more dense and milky texture that's less creamy than ice cream. It's not thin, but it lacks the plush, buttery fullness of its American cousin. Some say that gelato has a more intense flavor than ice cream, since it has less of the tongue-coating cold fat that gets in the way of tasting things. But I think it's more accurate to say that gelato's flavors come through direct, hard, and fast, then melt away clean. A good, flavorful ice cream can have just as intense a flavor, but you'll taste it differently. One isn't necessarily more flavorful than the other.
Temperature's the Key
So if gelato has less fat than ice cream, and less air pumped into it, why is it not as hard as a brick? How does it get that super-soft, almost elastic texture that looks like a swirl of frosting more than a scoop of ice cream? It's the last big factor: temperature. Ice cream is best served at around 10°F; gelato cases are set to a warmer temperature. If you freeze gelato really cold, it'll turn right into the dense, relatively-low-fat brick it has the potential to be. But when warm, it's that perfect soft-but-not-soupy consistency. If you stored ice cream at a much warmer temperature, it'd get too soupy: the high fat in water emulsion would melt too fast.
A Scoop by Any Other Name
I've been following the common naming convention in this post, calling American-style ice cream "ice cream" and Italian-style "gelato." But here's the thing: gelato's just the Italian word for ice cream. Though it does stick to the tendencies I've pointed out above, individual recipes do vary. Some call for cornstarch, others for egg yolks; some use higher amounts of sugar and others use less.
But it's all ice cream, just how soft serve is just warmer, freshly churned ice cream, and frozen yogurt is just soft serve made with yogurt as the dairy base. Sure, we can quibble over names and definitions, but at the end of the day, it's all one happy frozen, creamy family. We can argue about differences, or we can sit down and dig in to a pint together? I know which I'd rather do.