I ran across an older post on water purification at the now defunct 36 Ready Blog — Water Purification: Simple and Inexpensive Methods. One of the many options for water purification was mixing the water with wine. Now to be clear, this method is a last resort; it is far from optimal. But wine is a common household staple, and knowledge is good.
I tracked down the original medical research article on which this claim is based. It’s from the British Medical Journal (very reputable) and was published in December of 1995. Here’s the full article from the National Institutes of Health website: Wine as a digestive aid: comparative antimicrobial effects of bismuth salicylate and red and white wine. The “bismuth salicylate” mentioned in the article is the active ingredient in Pepto-Bismol. [The test used 35 mg of bismuth salicylate diluted in 1 liter of water as the starting point for further dilutions.]
The article details experiments mixing water containing different types of pathogenic bacteria with either white wine, red wine, or bismuth salicylate. Different dilutions and lengths of time affected the number of bacteria remaining viable in the tests. A 1:1 dilution (one part wine, one part contaminated water) using white wine purified the water within an hour, reducing bacterial content (E. coli) by 105 (to 1/100,000 of the starting level). Red wine at 1:1 dilution took 2 hours for the same effect, and bismuth salicylate took 24 hours. At a 1:2 dilution (one part wine, 2 parts contaminated water), the white wine took 2 hours, and the red wine needed 24 hours. At a 1:4 dilution, both white and red wine took 24 hours to kill most of the bacteria.
So white wine was most effective in killing the bacteria quickly. Red wine worked just as well given enough time, up to 24 hours. But the researchers also determined that it was not only the alcohol in the wine that did the trick. A dilution of pure alcohol to the same alcohol content as wine had little effect. Tequila was also tested and found to be ineffectual. The wine works partly due to its pH and partly due to other compounds in the wine. The authors concluded: “The antibacterial property of wine is largely responsible for wine’s reputation as a digestive aid.”
Caveats: There are better methods of water purification than adding wine to the water. Boiling water for one minute (at a full rolling boil) is very effective. And certain water filtration devices are also excellent at purifying water. Purification of water with wine is an ancient method, used by millions of persons for many generations, so it works to some extent. But it is not the best method today.
Using wine also has the problem of adding alcohol to one’s daily diet. At a 1:4 dilution, with a 24-hour wait time, 2 glasses of wine (5 oz each) will combine with 40 oz of suspect water to give you 50 fl. oz or about 6 glasses of fluid. At a 1:2 dilution, you end up purifying only 20 oz of water for each 2 glasses of wine, which is just over 3 eight-ounce glasses of fluids. So wine is problematic as a water purification method.
But it’s also good to know. If you are traveling abroad and don’t trust the local water, a 1:2 dilution with white wine and a wait time of one hour will be helpful. But it’s not a fool-proof system.