It’s one of the most famous “experiments” in the viral margarine email: leave a tub of margarine in your garage, and within a few days, you’ll notice that not even a fruit fly will go near it. The claim is that because margarine is “nearly plastic” and has “no nutritional value,” nothing—not even teeny-weeny microorganisms will find a home to grow on it. The margarine garage test is a study in is not a test at all. It’s merely an observation with mistaken conclusions.
The observation that during the Margarine garage test, it fails to attract any flies may be valid. But does a lack of flies really prove a lack of food? Margarine is indeed incredibly stable. It was invented for stability. The idea that it’s an immortal, inedible substance like a Twinkie is pure fiction. In reality, there is a fascinating scientific reason why insects might pass it over, and it has everything to do with chemistry, not “plasticity”.
In this article, we’ll dive into the science of hydrolytic rancidity, explain why bugs prefer butter, and reveal what actually happens when margarine shuffles off the mortal coil.
Examining the Original Margarine Garage Test Viral Email
You can bet that the original margarine invented by Mège’s would not last forever. After all, it contained milk. But the compilation claims that margarine will never spoil, even at room temperature:
Open a tub of margarine and leave it open in your garage or shaded area. Within a couple of days you will notice a couple of things:
- no flies, not even those pesky fruit flies will go near it (that should tell you something)
- it does not rot or smell differently because it has no nutritional value; nothing will grow on it. Even those teeny weeny microorganisms will not a find a home to grow.”
Is it true Is margarine like a Twinkie? No. Not true. Not even a Twinkie is like a Twinkie. Although margarine is very stable (that’s the whole point), it will eventually go rancid, producing a sort of paint-like odor. Unsaturated fats, like vegetable and seed oils, go rancid faster than saturated ones, like animal fats and hydrogenated fats.
Hydrolytic Rancidity: Why Margarine DOES Eventually Go Bad
Can margarine go bad, then? You bet it can. Margarine will eventually go rancid from bacteria or mold colonization, and bacteria and molds have all been found in margarine, in the water phase, which usually contains added ingredients such as emulsifiers.
However, here is when things get truly interesting. Whereas vegetable oils are readily subject to oxidation rancidity, margarine, which contains an aqueous phase, as mentioned, is subject to a different type of rancidity, called hydrolitic rancidity. What happens is that, when moisture is present, fatty acids can be cleaved from triglyceride molecules by the enzymatic action of contaminating microbes.
This releases free fatty acids, resulting in rancid, off-flavors. Margarine is well protected from this because of the dispersion of the water droplets, but eventually, through rancidification or the action of microorganisms, it will go bad. 1Kilcast, David, and Persis Subramaniam. The Stability and Shelf Life of Food. Boca Raton: CRC, 2000. 2Das, Debajyoti. Biochemistry. 12th ed. Kolkata: Academic, 2005.
Pretty much any claim that a food product will never go bad should be ignored. There are no foods, even canned foods, that never go bad. Everything, eventually, is rendered inedible. Even canned water, like they used to store in the nuclear fallout shelters, had expiration dates! Keep in mind, however, that canned foods last many, many years after their printed use by dates.
Margarine Lacks What Flies Want
What do flies want? They want nice, putrid smells. This means they are attracted to the smells of rotting, decaying meat or sweet and fermenting plant foods, like fruit. In other words, they are attracted to foods that are undergoing breakdown due to microbial processes.
Margarine, through its stability, is not readily subject to such microbial assault because it is an inhospitable environment. The type of breakdown that initially occurs in margarine as it sits in the warm garage does not produce smells that attract flies. This doesn’t mean that it’s not food. Many cooking oils are highly stable at room temperature. This is especially true of oils with high saturated fat content. Such an experiment using these oils would produce similar results. This does not mean that a cooking oil is not food.
Since margarine is a stable oil-in-water emulsion that has added salt and sometimes preservatives, it restricts the growth of organisms. It does not, however, eliminate it. However, if left long enough, margarine will eventually begin to be colonized by fat-degrading bacteria, which will break down the fatty acids. If the margarine separates, such spoilage will occur more quickly. Margarine spoils very slowly, but it does eventually spoil.
The Final Verdict on the Margarine Garage Test
The viral “garage test” fails because it confuses a high shelf-stability with a lack of food value. While it’s true that margarine’s unique water-in-oil emulsion makes it less attractive to flies and more resistant to standard molding than butter, it is far from immortal. Through the slow but inevitable process of hydrolytic rancidity, the fats eventually break down, proving that even the most stable spreads are subject to the laws of chemistry. A similar viral myth about how American cheese doesn’t burn when exposed to a direct flame is also due to the properties of an emulsion.
Don’t let an internet chain email dictate your grocery list. Margarine isn’t a “plastic” experiment; it’s just a highly engineered food product with a very specific scientific shelf life.
To see how this myth fits into the larger, bizarre history of this spread, head back to our Complete Guide to Margarine Myths and History.
