Here's What You Should Know About The White Clumps In Your Starbucks Drink

Most of us probably order Starbucks because we like the taste and need our caffeine fix, but some of us may also end up posting a photo to our Instagram or other social media accounts if the drink happens to look extra pretty or appetizing. However, one Starbucks customer recently had the opposite experience. Reddit user u/Sad_Permission was taken aback after noticing strange-looking white clumps gathering at the bottom of their soy venti pistachio iced latte, prompting them to post a photo of the beverage on the social media platform. "Is it OK to drink?" the post asked. "I can't figure out what this stuff is since I ordered with soy and not dairy milk."

Luckily, fellow Starbucks fans were quick to assure the OP that there is nothing harmful about the white clumps of soy milk that can sometimes pool at the button of a coffee drink. "It's sediment from the soy milk. It's harmless to drink but it can occur if the box isn't shaken, or even if it's almost empty and they poured the last of the soy milk into your drink," former employee u/BirdBarista explained in the comments.

Soy milk has a tendency to curdle when added to coffee, because coffee is an acidic beverage. Soy milk has a "curdle point" of about pH 5.5, while most coffees have an pH level of about 5 (via Melanie J Kirk). Therefore, when soy is mixed with coffee, it becomes closer to the pH level of coffee, causing the soy proteins to coagulate and clump. According to Coffee Detective, this is more typical in hot drinks, since heat also hastens the break down of soy proteins, although many other factors, like the acidity levels of the particular brand of coffee and how quickly the soy is mixed into the drink, can also cause soy milk to curdle into "instant tofu."

While the venti Starbucks latte found on Reddit may not really be "curdled," the process of mixing soy with acidic coffee can still cause bits of soy particles to separate and clump if the drink is not mixed together properly. So although it might not necessarily look appetizing, these white clumps are fairly common and typically nothing to worry about, as long as the drink still tastes fine. 

In fact, other users suggested this can be an easy way to ensure that the barista didn't actually hand them a drink with real dairy. "I have historically used them to confirm my drink is soy if it tastes off," u/RaptorClaw27 replied. "I call them 'curds of confirmation' bc it means it's definitely not dairy," another user joked.