Is it safe to drink wine that has a fruit fly in it?

You've just poured yourself a glass of your favorite white wine, chilled to perfection. You're about to take that much-anticipated first sip when a fruit fly lands in your glass. Worse yet, the fly is clearly dead. Given what we know about the unsavory habitats these flies frequent, a nagging question arises: Is it still safe to drink the wine?

Despite their seemingly benign name, fruit flies, or Drosophila, are often found around decomposing food. They gravitate towards garbage bins, compost heaps, and other places where food falls, including drains. The decaying food they favor is rich in microbes that the flies can pick up and carry to the next surface they land on. This may include bacteria like E. coli, Listeria, Shigella, and Salmonella.

Any of these bacteria could potentially lead to severe infections, even in healthy individuals. Given this, it may seem logical to pour the contaminated wine down the sink and opt for a new glass.

Contrary to instinct, scientific evidence suggests that doing so would most likely result in wasting a perfectly good glass of wine. Most wines contain between 8% and 14% ethanol and have a pH level ranging from 4 to 5. A pH level under 7 is considered acidic, which is not conducive for bacterial growth.

It's well-known that alcohol is a germ inhibitor. This property is one reason why wine can be preserved for extended periods. Multiple laboratory studies have also shown that the combined effects of wine's ethanol and organic acids, like malic acid—found in grapes and wine—can inhibit the growth of E. coli and Salmonella.

Since all types of wine—red, white, or rosé—are naturally antibacterial, the microbes transferred by a fruit fly would be compromised, reducing their potential for causing infection. Therefore, it's highly likely that the wine could be consumed without any adverse effects.

Whether or not the microbes transferred by the fruit fly to the wine lead to an infection also depends on the metabolic state of the microbes. If the wine in question was chilled, this further works in your favor. Lower temperatures profoundly alter the metabolism of some bacteria involved in food poisoning, effectively inhibiting their growth.

Moreover, if any germ does survive the wine's defenses and you consume it, it still has to contend with the highly acidic fluids in the human stomach. Most bacteria that cause food poisoning are extremely sensitive to acid, which can damage their DNA. Specifically, stomach acid can even kill these bacteria. In the stomach, germs also have to overcome other potentially lethal barriers, such as digestive enzymes, mucus, and the ever-watchful immune system defenses.

In summary, it's highly unlikely that microbes transferred by a fruit fly into a wine glass would lead to an infection. Unless you have a phobia of germs, the sensible approach would be to remove the fly and proceed to enjoy your wine. If you're looking for additional protein, you could even swallow it. It won't alter the taste, and your digestive system will process the fly just like any other protein.