Here’s What Probably Happened to the Milk in That Bizarre Reddit Video

A couple of days ago, a Reddit user posted a strange and stomach-churning video from her kitchen (please, only watch after you’ve finished eating lunch). In it, a companion is holding a carton of what she claims is brand-new milk over the sink. Right away you can see what appears to be a strand of milky-white liquid dangling off the side of the carton. Then, her companion begins to pour the milk into the sink, and that’s where things get gross: The milk emerges from the carton in a thick, molasses-like stream.

The narrator of the video claims she’s just popped the tab on the carton, and that the expiration date reads February 11, 2019. So what exactly happened to her milk that it would seemingly out of nowhere turn to syrup? We asked an expert to weigh in.

Scott Rankin is a professor of food science at the University of Wisconsin-Madison (where they really know their dairy). He took a look at the video himself, and while he wants to make it clear that he hasn’t seen the milk in person or analyzed it, he can probably guess what happened to the milk: It fermented.

Usually, when people imagine milk that has gone bad or is undrinkable, the first image that comes to mind is chunky milk. This is an entirely different process: An exo poly saccharine lactic culture caused the milk to become “ropey,” Rankin explains. This bacteria has other applications in foods that are safe to eat, like yogurt, but liquid milk that has been fermented should under no circumstances be consumed.

“Whatever food you buy, whether it’s milk or cheese or canned peaches, you should expect it to perform like you bought it. If it doesn’t, that means somewhere along the way it was not stored or manufactured [correctly],” says Rankin.

Rankin jokes that he and his six kids, who go through gallons of milk every week, have never encountered fermented milk, and even in his professional life, he’s never gotten a call regarding ropey milk (until now), which means this is a rare phenomena. Although he can’t be sure, he says it’s possible that the fermentation happened before the woman in the video brought it home.

In order for milk to ferment, it needs “some sort of inoculation [like a starter culture] and then we need warm temperature.” Once the milk gets those two elements, it can take as little as seven to eight hours to ferment. That means it might have already been undrinkable when she bought it at her local Costco, and there was nothing she could do to prevent it in her own kitchen. So no, you don’t have to replace your fridge on the off chance you have a similar experience with your milk.

Rankin again emphasizes that even though edible products like yogurt go through this same process, you should not “spend too much time thinking about whether or not it’s safe to drink.” Go back to the store, ask for a refund, and buy a new carton of milk. It’s highly unlikely you’ll get a dud like this twice in a row.