Why does mineral water have an expiration date?

Mineral water itself has no shelf life. Underground, in the aquifers where it is stored, even if millions of years pass, the water will still be good and protected from contamination. The roll starts when the water is bottled. “Water is very susceptible to external contamination. If the bottle is not properly closed, the liquid can come into contact with bacteria in the air and become contaminated. It’s rare, but if there are harmful microorganisms in the environment, mineral water can even cause physical symptoms, such as diarrhea”, says biochemist and sanitary specialist Petra Sanchez Sanchez, from the Brazilian Association of Mineral Water Industries (Abinam). Problems can also happen even with the water turned off. Temperatures above 35ºC increase the possibility that the natural bacteria in the water will multiply, altering the smell and taste of the liquid. To reduce the chances of these incidents, bottled water has an expiry date, which varies according to the quality of the packaging. A glass bottle, for example, has a longer shelf life than a plastic one because it can isolate the liquid from contact with ambient air for a longer time.