An 8-year-old box of Twinkies has disproved the myth that the Hostess product never goes bad. Upon closer inspection, it also revealed that the snack may decompose differently than your average foodstuff. As NPR reports, the varying mold growth on the Twinkies was so unusual, it caught the attention of fungi scientists.

The story of the putrefied pastries began in 2012, when nature photographer Colin Purrington learned of Hostess Brands' impending bankruptcy. Fearing Twinkies would disappear from shelves for good, he bought a box for posterity. It sat in his basement until he was hit with a junk food craving earlier this year.

When Purrington ripped open the 8-year-old package, he was surprised to find that the snacks inside were inedible. He had assumed Twinkies were indestructible, but the contents of the box proved otherwise: The cake he had bitten into tasted like what he described as "old sock," another one had a dark spot on it, and a third had shriveled up and turned gray.

After Purrington shared photos of his discovery online, he sent the Twinkies to Brian Lovett and Matt Kasson, scientists at West Virginia University in Morgantown who specialize in fungi. In the past, the researchers have studied how well fungi grow on preservative-laden food, like Peeps. They suspected that fungal growth was responsible for the Twinkies' decay—they just didn't know what kind.

The shriveled-up Twinkie appeared to be shrink-wrapped in its wrapper, a result of the fungus inside consuming more gases than it produced. The fungus may have stopped growing once it ran out of air in the package. When they unwrapped it, the scientists encountered a rock-solid material they needed a bone marrow biopsy tool to penetrate. The Twinkie wasn't hard all the way through, however: The soft, creamy center survived, suggesting the fungi was more attracted to the cake than the filling.

Samples of the Twinkie marked with the dark circle pointed to the presence of Cladosporium, one of the most common airborne molds found indoors. The researchers haven't been able to obtain a living spore sample from the hardened pastry, but they're still trying. Further lab dish tests will hopefully reveal the species of fungi that mummified one of the world's most shelf-stable baked goods.

[h/t NPR]