'Big Mac' Did Not Rot for 31 Days... The Reason Given by the Hamburger Company [Hamburger Rotting]④

Checking the Spoilage Speed of Burgers from 6 Companies
Five Guys Covered with Mold Over 80%
Mamstouch and KFC Also Expanding
Rotteria Bun Bottom Part Undergoing Spoilage

It has been a month since the Asia Economy Food and Beverage Team began an experiment to observe the truth behind the viral rumor on YouTube and social networking services (SNS) that "hamburgers do not rot." Among the representative products of six companies?McDonald's, Mom's Touch, Lotteria, Burger King, KFC, and Five Guys?five burgers, excluding the McDonald's Big Mac, showed clear external changes such as mold growth on the buns and patties and volume reduction due to moisture evaporation.

Hamburger Decay Experimental Group

The Lotteria Bulgogi Burger, which had the slowest decay rate along with the Big Mac, showed white mold the size of a finger joint and black spots in a band shape on the bottom bun after 30 days of the experiment. All the vegetables had dried out and were not visible externally, and the patty was completely dry, making the entire burger appear shriveled as if compressed. Generally, decay started mainly at the bottom part of the product.

Except for the Big Mac... Experimental Hamburgers Decayed Rapidly Over One Month

One month into observation, the condition of McDonald's Big Mac (left) and Lotteria Bulgogi Burger. Photo by Yoon Dong-ju

The Big Mac, which uses a double-layered patty, had mold the size of a thumbnail growing on the bottom bun, but the color and shape were not prominent. The overall shape of the burger, including the top bun sprinkled with sesame seeds, showed little difference compared to the beginning of the experiment. Ingredients such as shredded lettuce and cheese were also visible to the naked eye.

The other experimental groups, which had already undergone significant decay, showed completely changed appearances over the month. The Bacon Cheeseburger from Five Guys, which showed the earliest changes, was covered with bluish-green mold on more than 80% of the product by this day. The mold extending to the patty and bottom bun turned dark gray, and except for the melted cheese, it was difficult to recognize the shape of the contents. The Burger King Whopper also had the upper part of the bun covered with cement-colored mold. The product was completely dried out with all moisture gone, and the burger size had shrunk compared to the start of the experiment.

The decay of chicken patty products like Mom's Touch Cyburger and KFC Zinger Burger also worsened significantly. The Cyburger had bluish-green and yellow mold spreading in a cloud shape on the top bun, similar to the two-week progress of the Five Guys Bacon Cheeseburger. The chicken patty was partially left but was decayed. The Zinger Burger had mold growing on about half of the top bun in a burnt-like pattern, and bluish-green mold spots appeared sporadically on the other half and parts of the patty.

Why Does Decay Speed Differ? Hamburger Companies Respond

Each brand selected for the experiment is closely monitoring the weekly updates. So far, observations show that most hamburgers decayed much faster than expected. Five Guys, which showed significant changes, emphasized that "they do not use any frozen products and maintain freshness by checking ingredient conditions twice daily, in the morning and afternoon."

After one month of observation, the condition of Five Guys Bacon Cheeseburger (left) and Burger King Whopper. Photo by Yoon Dong-ju

Other manufacturers also highlighted that they do not use any food preservatives in buns, vegetables, patties, or other ingredients. Currently, KFC, Mom's Touch, Lotteria, and Burger King are known to receive buns from the same supplier. Manufacturers with global headquarters like McDonald's and Five Guys have their own contracted suppliers. They believe that differences in the speed of mold growth and spread depend on the composition of raw materials in each product.

Regarding the relatively delayed mold growth on the Bulgogi Burger, Lotteria explained, "All raw materials undergo sterilization, disinfection, and heat treatment, so the number of microorganisms that cause mold growth is low." They added, "Unlike other experimental groups, it does not contain high-moisture ingredients like tomatoes or pickles, making it difficult for microorganisms to grow, which likely results in slower spoilage."

After one month of observation, Mom's Touch Spicy Burger (left) and KFC Zinger Burger. Photo by Yoon Dong-ju

Products using chicken patties have a batter coating that acts as a protective layer, so moisture from tomatoes or vegetables is absorbed mainly by the bun instead of the patty, creating an environment conducive to mold growth. Beef patties grilled on a hot iron plate retain meat juices, which can accelerate the decay of buns and other ingredients. Additionally, the industry explains that cheese, made by fermenting milk, can influence the decay speed of other ingredients when exposed to room temperature.

Applying this, the Five Guys Bacon Cheeseburger, which contains thick layers of cheese, beef patties, tomatoes, and various vegetables, provides optimal conditions for microorganisms to grow and multiply. The Lotteria Bulgogi Burger has a relatively simple composition with patty and lettuce. However, the McDonald's Big Mac contains two beef patties, pickles, and lettuce?ingredients with high moisture content?and cheese, creating conditions favorable for microbial growth, yet its decay speed is significantly slower. McDonald's stated, "Various companies, including ourselves, receive patties, buns, and vegetables from the same supplier," and added, "We have no special position regarding the experiment."