You’ve probably heard or have seen the internet stories about how supposedly a McDonald’s burger will not rot. The facts that we do know about McDonald’s burgers is that when it is left out in the air it will not grow mold. Another thing we know is that in order for mold to grow, the following things need to be present: mold spores, air, moisture, and a hospitable climate. Many believe that the reason behind this non-decomposing phenomenon is because there are a lot of chemical preservatives inside the burger, making it an inhospitable environment for mold to grow.

Scientists have experimented with McDonald’s burgers and have brought up multiple theories as to why these burgers simply will not rot. They have stated that one reason could be that these burgers have a high salt level and is preventing the decomposition. Others believe that the small size of a McDonald’s burger is allowing it to dehydrate so fast enough that there is not enough moisture present for mold to grow in.

Of all the theories, one that seems to be quite possible. It states that the reason behind the burger not being able to grow mold would be because there are no mold spores present on a burger from McDonald’s, or in the air in or around where the burgers may have been stored. Even after all of these theories, we do now know that McDonald’s burger do indeed rot and decompose…under certain circumstances.

When asked about whether or not there was an explanation about all of this burger chaos, Dr. Keith Warriner, the program director at the University of Guelph’s Department of Food Science and Quality Assurance, he responded by saying, “There have been a lot of online videos and photos touting the fact that when left out for an extended period of time, a McDonald’s hamburger does not rot and that this is because they are laden with chemicals. The reality is that McDonald’s hamburgers, french fries and chicken are like all foods, and do rot if kept under certain conditions. Essentially, the microbes that cause rotting are a lot like ourselves, in that they need water, nutrients, warmth and time to grow. If we take one or more of these elements away, then microbes cannot grow or spoil food.”

Using a McDonald’s burger as our prime example, we have found that the patty loses water in the form of steam when it is being cooked. The bun, of course, is made out of bread. So toasting it reduces the amount of moisture. This means that after the preparation, the hamburger is left pretty dry. But when left out in the open in a room, there is more water loss as the humidity in most buildings is around 40%. So, in the absence of moisture or high humidity, the hamburger simply dries out, rather than rot.

So there we have it. A McDonald’s burger isn’t exactly an “everlasting burger”, it will decompose like all other foods. It just requires a longer process! Myth busted.