Does Your Kirkland Signature Brand Milk Have Dark Specks In It? This Is Likely The Cause

We may receive a commission on purchases made from links.

You pour a glass of Costco Kirkland Signature reduced-fat milk, ready for a sip, and notice dark specks. This experience has become somewhat common for Costco fans posting online, but fear not, fellow milk enthusiast, for the mystery of the dark specks is likely far less sinister than you imagine. According to a top Reddit comment by user Gold_n_Tomato, a purported milk pasteurizer, the culprit is often powdered milk.

"Reduced-fat milk has powdered milk to raise the protein content," the commenter explained. "The dehydration process sometimes scorches the powder. Totally safe." This explanation aligns with information provided by the American Dairy Products Institute, which explains that these dark specks are essentially overheated dairy powder. When powdered milk becomes too hot during drying, it can create harmless, albeit unappetizing, tan, brown, or black specks. This is a Maillard reaction. The Maillard reaction is what happens when proteins and sugars in food react to heat, creating browning.

But why are these specks seemingly only in Kirkland Signature reduced-fat milk and not all reduced-fat milks on the market? It could be a cost-saving measure on Costco's part. Another commenter noted that it's cheaper not to add a filtering step to remove the specks like other, more expensive brands might.

A poster identified as Timothy Sly, professor emeritus of Public Health and Epidemiology at Toronto Metropolitan University, offered a slightly different explanation for the specks on Quora. "The most common reason for this is that the carton was held a little too long in the sealing stage (where heat is applied to the waxed carton), probably due to the line being stopped momentarily," Sly explained. "The extra heat causes some scorching of the inner lining, which can fall into the milk. It can also be due to detritus being in the carton before filling." 

Sly's theory points to a potential hazard, as there's no way of truly knowing what's floating in your milk. As the adage goes, "When in doubt, throw it out." But how can you tell if what you see in your milk is from scorching or something else? As Gold_n_Tomato shared, if the stuff you see in your milk is specks (rather than larger floating bits), it's likely from scorching and won't harm you. So, while those specks in your Kirkland milk — which ranked No. 13 on Daily Meal's ranking of the 15 best milks – might look strange, they're usually just a harmless byproduct.

If you still feel "icky" drinking milk with visible specks, try using it in recipes. For instance, using milk to cook pasta is one of seven alternatives to try instead of water. Once you add sauce, the specks will disappear. Alternatively, make a delicious coffee milk with coffee syrup, such as the Eclipse brand on Amazon, mixed with milk. Simple, satisfying, and you won't see the specks!