What's Growing in My Crisper Drawer?

In the late 17th century, Dutch scientist Anton van Leeuwenhoek looked through what was then an extremely powerful single-lens microscope, and became the first person to directly observe bacterial life. It took two centuries before anyone realized that these same organisms caused many infectious diseases.

But today, even children understand that our world is teeming with microscopic life, and that certain environs foster its growth. Bacteria is what causes disease, spoilage, and decomposition—and it's also what creates those nasty stains in your refrigerator. In honor of scientific tradition,and household curiosity, let’s look at some germs.

Life Forms You Can See

Spoilage Bacteria — These are the bacteria your mother warned you about, even though they're basically harmless. They cause bad tastes, nasty smells, and off-colors in foods that have been sitting in your fridge for too long. While it’d be imprudent to call them all safe, most species will not make you sick. Rotten meat is the exception, though, as meat spoilage usually creates toxins that remain in the flesh even if recooked. Don't mess with spoiled meat.

Spoilage will occur no matter how awesome your refrigerator is. It's just a matter of time. However, you can delay the inevitable by keeping temperatures low, minimizing light exposure, and sealing foods in airtight containers. Also, keep an eye on expiration dates, and be wary of strenuous refrigerator conditions that may hasten spoilage (such as high humidity or rising temperatures). As mentioned, rotten foods are not likely to cause sickness, but their smell may corrupt other stored foods and, at the very least, taste awful.

Mold — Bacterial growth, although a concern, does not usually manifest as stains; that's fungus. Fungal mold is everywhere. If you’re a fan of blue cheese or salami, you’ve eaten it. Like bacteria, most molds are harmless, but this doesn’t mean you should let fungal outgrowths take over your fridge, lest your food be contaminated and your health compromised.

We associate fungi with warm environments, but humidity is just as important. That means your moisture-retaining refrigerator and the food inside it are vulnerable. Mold is actually a more serious threat to your refrigerator than bacteria. Some molds can even tolerate saline environments—even cured meats can go bad. Whereas bacterial spoilage slowly degrades food, turning it brownish and smelly, mold takes the form of an actual growth—usually a white or blue color—on the contaminated object.

The most dangerous—and frustrating—thing about fungal mold is the method by which it reproduces: spores. If you can see mold, whether on food or in the back corner of your crisper drawer, it means tiny invisible fungal spores are all over the interior of your fridge. The seeds are already planted for future infestations and stains.

Keep in mind, molds are merely the tip of the iceberg—in that they are the “seed head” of a fungal growth that has already burrowed its way into a host. Furthermore, the organism’s spores are microscopic and have the capacity to spread throughout the interior of a fridge. This means items that come in contact with food—dishtowels, utensils, bowls, etc.—may also be contaminated. Symptoms from eating mold depend on the type and amount ingested, but they can range from mild diarrhea and vomiting (more common), to serious illness and death (less common). So, clearly, any effort to sanitize your fridge should be tackled with extreme prejudice. And this leads us to our next, more serious topic...

Life Forms You Can't See

Pathogenic Bacteria — These bacteria are particularly nasty, as they are the most harmful, but they display few warning signs. According to the U.S. Department of Agriculture, they don't generally affect the taste, smell, or appearance of contaminated foods. So it’s easy to eat these bugs by accident, and if you do, you’re going to have a bad day. Fortunately, the whole point of a refrigerator is to prevent these creepers from growing. As long as temperatures stay below 40°F, they generally aren't a problem.

But there are some strands of bacteria that can withstand, and sometimes even thrive, at extremely low temperatures. They are called psychrophiles.

Psychrophiles — These creepers are mostly bacteria and archaea (single-cell organisms similar to bacteria). While uncommon, they pose a more serious threat because some species can survive freezing temperatures. Among the most dangerous of these germs is Listeria monocytogenes (or simply listeria), which can grow at temperatures as low as 1 degrees Celcius. In 2011, a listeria outbreak from a cantaloupe farm in Colorado caused 30 deaths throughout the country.

Bacteria that can survive your fridge can come from unsanitary conditions in the fridge itself, but more likely from compromised animal products like rotten dairy and spoiled meat. They carry other disease-causing agents like E. coli and Vibrio, too. Other strands of psychrophiles, such as Pseudomonas, merely cause food spoilage.

To be clear, it’s extremely unlikely that pathogens will spontaneously break out in your refrigerator (unless you live in absolute filth and squalor). The true threat comes from outside—that is, contaminated foods brought into your home.

Okay, But What Can I Do About This?

Periodic cleaning or your refrigerator (and kitchen) is the best way to limit risk—mostly to prevent fungal intrusion, but bacterial as well.

Some molds can be really tricky to remove, but there are plenty of strategies for tackling such a problem. If you discover mold on any unsealed food in your refrigerator, throw it away, along with any other exposed foods. It sounds drastic, but certain molds can produce poisonous substances called mycotoxins. And those are not to be trifled with. The USDA recommends doing the following:

“Clean the inside of the refrigerator every few months with 1 tablespoon of baking soda dissolved in a quart of water. Rinse with clear water and dry. Scrub visible mold (usually black) on rubber casings using 3 teaspoons of bleach in a quart of water.”

You should also keep dishcloths, towels, mops, and sponges clean and fresh. Toss any items that smell funny or cannot be cleaned. Here’s a good forum discussion on various ways to clean the must stubborn mold stains. Baking soda is another popular method for getting rid of stale odors and removing food rust.

If you notice that mold growth is becoming a consistent problem, there’s a deeper issue afoot. Most likely, you’re either not properly sanitizing the fridge, or you’re overlooking a critical source of moisture, such as a leak. Either way, be thorough in your cleaning and keep an eye out for irregularities. When it comes down to it, if you have a hunch that something is contaminated, it probably is.

Photo: Flickr user hungaro phantasto, Creative Commons