We all know that moment when you drop a piece of food on the floor and have to make the quick decision of whether you want to eat it or not. Is the five-second rule really safe? Are we putting ourselves at risk of getting sick? I’ll admit that I have eaten food that I’ve dropped on the floor, which is why I wanted to look into the effectiveness of the five-second rule.
I first looked into some basic statistics about bacteria. The Centers for Disease control found that food contamination, from being dropped on the ground, was the 6th most common factor for food poisoning out of 32 outbreaks. Further, a study done in 2015 stated that out of the 9,000 types of microscopic organisms in our homes, 7,000 are mostly harmless bacteria. Bacteria is everywhere, even if we don’t realize it; researchers found that we release 38 million bacteria cells into the atmosphere every hour. Although most bacteria in our homes are harmless and can help us develop a stronger immune system, is it still two risky to eat food that has fallen on the ground?
I found a couple studies that explored the question of the degree that different foods are contaminated across different confounding variables: the surface of the ground, the moisture of the food and time.
The first experiment was performed in 2007 by Paul Dawson, which studied the survival time and contamination of Salmonella Typhimurium to sausage and bread using wood, tile, and carpet. The study concluded that 99% of the bacteria contaminated the sausage after 5secs on the tile. When compared to the wood and tile the sausage was contaminated less than 0.5% when it was dropped on the carpet. It was also concluded that the survival time for Salmonella Typhimurium is up to 4 weeks on dry surfaces and is in high enough populations to immediately contaminate food when dropped.
A second two year experiment was conducted by Donald W. Schaffner, a food microbiologist at Rutgers University, and Robyn C. Miranda, master’s thesis student, that evaluated different contact times using 4 different surfaces (stainless steel, ceramic tile, wood and carpet) and foods (watermelon, bread, buttered bread, strawberry gummy candy). The foods were dropped from 5in onto each surface which was pre contaminated with a bacteria like salmonella. The study used 4 different contact times(amount of time it took the food to hit the surface). The trials were replicated 20 times each, which gave 2,560 results. The experiment concluded that there was a direct relationship between the time food was left on the ground and the amount of bacteria that transferred. The carpet had the lowest transmission rate out of the 4 surfaces. Also foods that had more moisture collected more bacteria; the watermelon was contaminated the most and the gummy candy the least. Since the study was large and evaluated multiple confounding variables it can be concluded that bacteria contaminates food instantaneously.
Both studies agree that food is contaminated immediately when it is dropped on the floor. However, the longer the food remains on the surface and the moisture of the food are factors that can lead to more, or less transferred bacteria. Therefore, the five-second rule is up for you to decide. The evidence proves that your food will be contaminated, however, there have not been studies to prove if the amount of bacteria that transfers is enough to make you sick. In this article the scientists who performed these experiments discuss whether or not they follow the five second rule. They all have mixed opinions and it comes down to personal preference. I know that after reading about how quickly bacteria contaminates food I’m going to think twice before eating something I’ve dropped on the ground.