Why does a quarter pounder mold faster then a big mac?

Question

I did this for a science fair project

and my results were that the quarter pounder molded faster than the Big Mac

Answer 1

It doesn't...how did you determine this?  Did you do a scientific study?  There would be no difference, unless the bun used for one sandwich was older than another.

Answer 2

You just got lucky. Here is another experiment for you to try. Buy a plain hamburger (no mustard, ketchup, onions, or cheese), and put a date on it. In one year from that date, take out of the refrigerator and it will be as fresh as the day you bought it.

Answer 3

The quarter pounder might have fewer preservatives in it. Preservatives are added to food to keep it from molding or going stale as quickly.