You can usually eat refrigerated yogurt for up to a week after the printed expiration date, but unrefrigerated yogurt doesn't last nearly as long. According the US Department of Health and Human Services, you should throw out yogurt if it's been at room temperature for two hours or longer. So you can imagine my shock when I learned that shelf-stable yogurt is a thing that exists, because the idea of yogurt sitting on a shelf at room temperature without going bad defies everything I know about yogurt.

Needless to say, I was curious about how the heck this shelf-stable yogurt is made and wanted to understand why it doesn't need to be refrigerated. So when Gogo Squeez invited me to visit their factory in Chef-du-Pont, Normandy, France—a country where boxes of ultra-pasteurized milk that can be kept at room temperature are common and yogurt is delicious AF—to see how to make shelf-stable yogurt, I knew I couldn't pass up the opportunity.

So let's start with the basics. Gogo Squeez Yogurtz (yes, it's spelled with a "z") launched in 2016. It's a shelf-stable yogurt that can be kept at room temperature for up to a year without going bad. For a year. It also comes in a cute little handheld pouch, like the adult version of the yogurt tubes of my childhood, so that's fun. And though this product sounds super high-tech, it turns out the process of making Gogo Squeez starts just like the making of any other type of yogurt: with lots of milk. Gogo Squeez collects milk from 65 local farms, all located less than 20 miles from their factory. A single farmer collects about 1,600 liters of milk from its cows in a single day, all of which is then trucked over to the plant. If you're doing the math, that's over 100,000 liters of milk every day.

Once at the plant, the milk is pasteurized—or heated up to kill any potential pathogens—in giant tanks, to which natural cane sugar; pectin, a plant starch that makes liquids thicker; and lactic acid-producing bacteria are added. These live bacterial cultures do the work of turning milk into yogurt during a fermentation process, which lasts about ten hours. A yogurt's tanginess, as well as the health benefits of yogurt from probiotics, come from those bacteria. 

After it's fermented, the yogurt is then put into storage tanks that can hold 10,000 liters of product until it's ready to be packed into handheld pouches. But this yogurt, even after it's sealed in those airtight pouches, still isn't shelf-stable. It's the next step that turns the otherwise ordinary yogurt into a product that can sit on grocery store shelves unrefrigerated.

The process of making dairy shelf-stable isn't anything new, even if its application to yogurt is somewhat novel. In fact, the French factory at which Gogo Squeez is produced has been making shelf-stable dairy desserts for over 60 years. The process by which this yogurt becomes self-stable is similar to the way those cans of pudding are treated.

The little handheld packages of yogurt get heated in a process called retort packaging. Pallets of the yogurt are placed inside what's best described as a giant, industrial pressure cooker, and they're heated at high temperatures and high pressure in order to sterilize the inside and kill off the bacteria. It's the same way that the milk was heated up to kill bacteria at the beginning of the whole process. 

After these pouches have been heated, there's nothing inside the pouch that could possibly grow into something that'll make you sick. The package is also fully sealed, so there's no way for other bad pathogens to get in. And since the yogurt has already been exposed to super-high heat, room temperature is no big deal. (If you've ever tried your hand at canning, this concept probably sounds familiar, just on a much larger scale than with what you'd do in your kitchen.)

The heating process does change the yogurt in a couple of critical ways. First and foremost, the texture changes, though this is something that the food scientists at Gogo Squeez adjust for in the original recipe. When it gets pumped into the packages, the yogurt is pretty thin, more liquid than yogurt. After it goes through retort, it thickens up so it has the feel of a more traditional yogurt. 

The sterilization process of retort also kills all bacteria, both bad and good. That means GoGo Squeez doesn't have any of the probiotics that can be beneficial to human gut health. You know how yogurts with live cultures will list the bacterial cultures on the label? They aren't listed on a packet of Gogo Squeez, because there are none. But there are no preservatives listed on the label either, because the way to make shelf-stable yogurt is through a physical process, not a chemical one. 

That also means, however, that that yogurt isn't invincible. After all, at the end of the day, it's just milk and sugar and fruit purée. So like all shelf-stable goods, Gogo Squeez does need to be refrigerated after it's opened. But don't feel bad if you eat it after letting it sit unopened in your bag all morning. It'll be totally fine—if a little warm.