Why does mineral water have an expiry date?

(Published on 20 March 2007 in 'Women at Work' - W @ W - a supplement of the Daily Mirror, Colombo, Sri Lanka)

Went to spend the day with my Aunt, sweeties. It does really take a lot of persuasion and goading on my mother’s part to get me to visit her. She has an answer for everything – and will pull out an encyclopaedia published in 1935 to quote her facts! I thought I’d gift her, a new set of Britannica Encyclopaedias but that would mean more arguments and more conflicting opinions.

As I helped her make tea I noticed quite a few mineral water bottles lying on her kitchen shelf. You have to use those up I advised as they too have an expiry date. She looked in disbelief. “Water… has an expiry date? Isn't the water we drink everyday about three billion years old? It hasn't hurt us yet has it?” I let that pass but decided to do a little research on my own.

About 70% of the earth is covered with water. But most of it is unavailable for human consumption unless it is processed first. Water contains various minerals - some good and others not so good for our health. Mineral water, as the name suggests, contains various minerals and traces of elements. It is usually measured as the residue left when a litre of water is evaporated.

It is believed that the minerals in mineral water have various effects on the health of a person. However, apart from the obvious function of providing clean and pure water to the body, studies have shown that there is no significant effect of mineral water on the health. Mineral waters do contain minerals, but the ability of the body to absorb them from the water is as good as negligible.

Still mineral water normally bears an expiry date. However, it does not mean the product is sub-standard after this date. Over a period of time, the composition of mineral water, changes. Usually, this change is not much. But even then it is essential that the consumer be informed that the composition of water, in other words the percentage of minerals in the water has changed in comparison to that specified on the label. The expiry date on the bottle denotes this time – when changes are likely to take place. Government agencies, like the Chief Food Authority (CFA), The Food Control Administration Unit of the Health Ministry and the Sri Lanka Standard Institution (SLSI) regulate the quality of bottled mineral water and have stringent regulations in place to monitor what is available in the market.

Sparkling water on the other hand has a limited shelf life, due to the carbon dioxide. PH indicates water acidity level. PH value between 6.5 and 7.5 is considered neutral. Mineral water should be as neutral as possible. Adding CO2 to water increases its acidity. Carbon dioxide in sparkling water slowly dissipates through the walls of the plastic container and the plastic caps. Sparkling water in glass bottles with metal closures has a much longer shelf life.

Even though mineral water, way past its expiry date would still be a better option to consume than regular tap water - I have begun to check the label before I buy a bottle. I am looking forward, to visiting my Aunt once again to share with her my new found knowledge. Also wanted to leave her with some needling questions that I came across:
If someone invented instant water what would they mix it with?
Where do they get Spring water in the other three seasons?
If pure water is so good for you, how come you never see any fish in it?

Will keep her busy and out of people’s way for a couple of days.

Miss Know-All
miss.know.all@gmail.com