The Burger Experiment: Will a McDonald’s Burger Ever Rot?

My kids heard the rumor that if you put a McDonalds hamburger on a shelf, it won’t change. The thought being that it is so filled with preservatives that it never rots; it stays exactly the same. So last year, for their science fair project, we decided to get to the bottom of the rumor. We bought 2 McDonalds hamburgers and fried up a homemade burger to see if they would age the same way.

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We used 3 burgers:
a) one homemade burger on a plate;
b) one McDonald’s burger exposed on a plate; and
c) one McDonald’s burger that was tightly wrapped in saran wrap.
(I’d love to show you the photos, but I put my phone through a wash cycle and lost them all. And like an idiot, I hadn’t backed up my phone in 8 months.)

The conditions: All 3 buns and burgers sat on shelf in a room that was 72 degrees for 4 weeks. We didn’t touch them or move them except once a week to examine them. (Miraculously, we didn’t get bugs or mice either!)

Purpose: To find out if they would age the same way during the month.

Hypothesis: We thought the both of the Mcdonald’s burgers would stay the same because of preservatives that they use. We thought the homemade burger would get stale and harden.

This is what we found:
Each week, we wrote down our observations. After about a week, the 2 exposed burgers hey didn’t look that different but their buns and patties were growing hard. The wrapped one was still soft. As time went on, the exposed burgers started to shrink and get darker as their moisture evaporated into the air. By the end, the meat patties were tiny, black and hard. The buns cracked and were hard too. When we opened up the wrapped burger, it was the same size but covered in mold.

What We Learned: We were relieved to see that the McDonald’s hamburgers decomposed in the same way as our homemade burger. The moisture escaped into the air causing it to shrink. Because the moisture escaped, it didn’t grow mold. The wrapped burger had the perfect conditions to make mold; the wrapping trapped the moisture in. Any food that contains water or fluid is susceptible to mold growth. McDonald’s also addressed this rumor on their site.

To find out more about how mold forms., kids can visit 

Want to experiment more? Check out our Kids’ Favorite Science Experiments

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Author: Heather Zachariah

Former Art Director for Home Magazine, Heather Leahy Zachariah, left her career in publishing after baby number number one. She now works from home as a freelance graphic designer and a chauffeur to her 3 busy kids. "Working on TipsFromTown has been a wonderful outlet for me. It renewed my love of publishing where I can design colorful, enticing pages online and allows me to share the things I love about being a mom." Heather grew up in Shaker Heights, Ohio, a place that still is near and dear to her. " After living in Brooklyn for 18 years and studying Graphic Design at Pratt Institute, she now lives in the Jersey burbs. "I love living so close to NYC, but in my heart, I'm an Ohio girl."