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Anatomy of a K-Cup

The Inner Workings of the K-Cup (Courtesy Smithsonian Magazine)

Keurig's K-Cups are everywhere. The machines are ubiquitous in homes and offices, and the company's signature K-Cups can be found in supermarkets, convenience stores, and through many online outlets. Customers love the variety (over 200 varieties available from Green Mountain Coffee) and a range of licensed vendors ranging from Starbucks, Newman's Own, Dunkin' Donuts, Peet's, and HiLine. They love the convenience. But how many of them have stopped to think of what's in their K-Cups? Let's peel back the lid and take a look.

Outside: The K-Cup has a tinfoil lid over a cup that's typically made of food-safe plastic in the Number 7 (polystyrene) family. The cup is made to resist moisture, heat, and light to keep its contents secure and fresh. A handful of companies, cognizant of customers' concerns over K-Cups' environmental sustainability, have experimented with alternative materials, though finding plastics well-suited to the Keurig has proven difficult.


Inside: Inside the K-Cup, you'll find a paper filter that's affixed with a food-safe adhesive, along with some ground coffee. While the plastic and foil on the outside help to protect against exposure to moisture, heat, and light, there are two more steps taken to ensure that the coffee doesn't go bad. First, the beans are typically allowed to degas (releasing the carbon dioxide that's a byproduct of roasting). Then, once the grinds are put into the cup, the air inside is switched with nitrogen, which is inert and helps prevent spoilage.

How It Works: Once you've gotten your K-Cups home, that's when things get interesting. The machine draws water from the water reservoir and heats it, then pumps it to the K-Cup chamber. The chamber in which the K-Cup sits contains two hollow needles of a slightly larger gauge than a marinade injector. One punctures the cup's foil top and fills it with the hot water that starts the brewing process, while the other punctures the cup's plastic bottom so the brewed coffee can make its way to your cup. The end result is a cup of coffee that ranges from competent to delicious. If you want a better cup of coffee, that means starting with coffee that's good, and fresh. We'll have more to say about that in our next post. In the meantime, you can also read more about upcycling and recycling K-Cups, and some of the most frequently asked questions about K-Cups that we've gotten here at HiLine.