It was 2 a.m. on a Sunday night in January 2016. Ben and Jerry's flavor guru, Kirsten Schimoler, had been at the ice cream plant in St. Albans, Vt., all weekend. Now she stood mesmerized in the wee hours as 180 cups of non-dairy almond "ice cream" whizzed past her every single minute.

At last, after nine months straight of testing and tinkering at the company's technical development center in the U.K., she had succeeded: The famous ice-cream maker was ready to launch its new line of vegan almond frozen desserts, with flavors like caramel almond brittle or chocolate fudge brownie, among others.

"It isn't easy to make a premium vegan 'ice cream'," says Schimoler of the company's frozen desserts. (Legally, they can't call it ice cream.)

Vegan "ice cream" recipes have been around since at least 1899, when a recipe for a peanut-based ice cream appeared in a Seventh-Day Adventist cookbook. But it wasn't until the 1980s that alternative "ice creams" came of age. Soy versions such as Ice Bean and Tofutti were all the rage, with Tofutti hitting sales of $17 million in 1985, spurring dozens of competitor brands.

The 2000s saw the rise of coconut, cashew and other vegan varieties. These days, vegan "ice creams" are easy to find in the freezer aisle, with everything from almond to avocado subbing in for dairy milk.

How do they do it? Mimicking the creaminess of milk without actual dairy is a big challenge. Milk may look surprisingly simple in its smooth, silky whiteness, but it's actually a complex choreography of water, protein, fat and sugar. When it's made into ice cream, each of those components plays a role.

Ben & Jerry's chose almond milk as its base because it gave the "best, most neutral canvas to let the flavors shine," says Schimoler. But none of the commercial almond milks contained enough almond to make a great frozen dessert.

Getting the vegan milk base right is crucial: Do it wrong and you end up with something that's icy and unappetizing.

"The high water content in many vegan milks is the enemy of the creamy mouthfeel," says Afton Cyrus, test cook at America's Test Kitchen in Brookline, Mass., and a contributor to the new cookbook Vegan for Everybody. This is because, says Cyrus, "non-dairy milks generally have high water content and low fat content, which creates hard, icy crystals when frozen."

The more water that is present as ice, the faster the product will melt, and those changes in melting affect the "creamy" perception.

"We make our own almond milk," says Schimoler. "We use coconut oil to mimic milk fat, and pea protein to mimic milk proteins."

Though the exact mix is proprietary, the goal is a homogeneous frozen dessert.

Both protein and fat are natural thickeners. And there's a big difference in the protein and fat content of dairy compared to soy, cashew, coconut, hemp and other vegan milks.

For instance, soy and pea-protein milks contain at least 8 grams of protein per cup — similar to dairy — while almond milk has only 1 gram. Meanwhile, dairy milk has 2.4 grams of fat, almond milk 3.5 grams and unprocessed coconut milk 57 grams of fat per cup.

For naturally low-fat almond milk, adding coconut oil, as Schimoler did, works well. Coconut oil is similar to butterfat and has been used for centuries to replace butter. Even so, coconut oil is a more saturated fat than that in dairy cream and freezes differently. If you see coconut oil at room temperature, it can be solid, so under freezing conditions it makes for a very firm product.

"Nondairy milk freezes really, really quickly!" says Schimoler. "I had set the ice cream-making machine to the usual freeze time and my first batch simply wouldn't budge."

Making vegan 'ice cream' "was so different than dairy that we had to throw out conventional approaches," she says.

Freezing temperatures can be altered by the specific types of sugars that are added: For instance, fructose will lower the freezing point of water nearly twice as much as sucrose. This may be one reason why you see both corn syrup and sugar in many vegan frozen desserts.

The goal for any ice cream is to evenly distribute tiny crystals of ice as well as air bubbles. "If you look at ice cream under a microscope, which I have done," says Schimoler, "you'll see thin slivers of ice embedded in a structure that is sort of like a kitchen sponge. The fats and proteins are working together with the air bubbles to create this fluffy, creamy food."

Because of its fat and sugar content, many vegan dairy producers say coconut is simply the easiest vegan platform to build a milk or cream out of.

"The fat influences how ice cream forms a film on the inside of your mouth and how fast it wants to slip down your throat, which influences the delivery of the flavor. You want your ice cream to linger a little," explains Donna Klockeman, a food scientist at TIC Gums, which manufactures ingredients that improve the texture and stability of foods for the food and beverage industry.

Cashew milk, like coconut, is a good base because of its higher fat content. But almond milk is still the No. 1 vegan milk choice among consumers, which makes it a popular choice for frozen desserts as well.

Today, Ben & Jerry's has seven almond milk frozen dessert flavors. Schimoler says she kept tweaking the ingredients until the end of the development process. "I was really fine-tuning it," she says. "I was working with the team to make sure we had really gotten to our signature, super-indulgent flavor and mouthfeel one would expect from Ben & Jerry's."

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