If you're a regular soda pop drinker, you may have noticed — perhaps with some alarm — that dark "stuff" tends to collect at the bottom of some soda pop bottles. At first glance it could be assumed the spots are on the outside of the bottles, the product of scuffing while in transit or while sitting on the shelf. Yet a closer inspection will often demonstrate movement, indicating the stuff is actually inside the bottles.

While this occurrence may be common across brands and flavors, it's particularly observable in light-colored beverages, most noticeably PepsiCo's Mountain Dew, as demonstrated during a recent trip to a major grocery store in which the author spent an awkward segment of his morning lifting two-liters above his head and staring at their bottoms.

Andrea Foote, senior manager of communications for PepsiCo Beverages Americas, wrote in an email that while it wouldn't be possible to say what the "stuff" that collects at the bottom of the bottles is for certain without having a sample to test, there is a likely explanation.

"Since Mountain Dew does contain some fruit juice there is occasionally sediment," Foote wrote. "This is a natural occurrence that happens occasionally — it can usually be rectified by lightly shaking the product to reincorporate the orange juice solids and does not have an impact on product safety or taste."

Fruit juice sediment seems a likely explanation — of all the other beverages recently examined by the author, the two that had the most visible "stuff" at the bottom were two-liter bottles of Coca-Cola's Minute Maid Lemonade and Pink Lemonade — and Foote's solution is accurate as well. The incidental jostling caused by taking the photo included in this post was enough to "reincorporate" most of the sedimentation.

Foote did have a final warning, however, issued in a followup email.

"I should have added that you should not shake right before you open the package since it is carbonated," she wrote. "That's why I said lightly shaking!"

Simon A. Thalmann is the online editor for Booth Features. He can be reached at sthalmann@kalamazoogazette.com.