The mineral water in my local shop has a label telling me it is from a 3000-year-old source, yet there is still a 鈥渂est before end鈥� date on it approximately two years in the future. If the water has been in its aquifer for 3000 years, why should it go off in a sealed bottle?
Mineral water has passed through layers of rock that have different effects on the water. Some minerals dissolve in the water, supposedly improving both its taste and health-giving properties, hence the demand for it.
The small pore size of the rocks the water passes through acts as a filtration system, improving the purity of the water by removing larger molecules such as biological contaminants. As soon as the water emerges it is vulnerable to contamination again. The 鈥渂est before鈥� dates are based on the amount of time the bottler believes the water will remain without measurable levels of contamination due to the lack of completely sterile conditions in their bottling plants.
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If the water is stored in a plastic bottle the date might also relate to contamination from the constituents of the plastic, which may change the taste of the water.
John Thompson, London, UK
The reason for the best before date on bottled spring water is not the contents but the container. Most mineral or spring water seems to be packed in polyethylene terephthalate (PET) bottles. During the manufacture of the bottles traces of catalyst or plasticiser, which may include antimony, remain in the plastic and are leached out into the water over time. To avoid this glass bottles, which have stood the test of time, are preferable.
Rob Davids, St Ives, New South Wales, Australia
鈥淧ure鈥� water does not decompose or suddenly go off. However, manufacturers of foods and beverages have to give 鈥渂est before鈥� dates to cover their backs. If the bottle sat around for long enough the plastic might decompose or the seal might degrade, allowing bacteria to enter and contaminate it.
As for the water being 3000 years old, most of the water we drink has probably been in existence as water molecules for millions of years. What is important is the purity of the water, not its age. 3000 years in an underground aquifer may have filtered out all the organic matter, but there might still be harmful dissolved chemicals such as arsenic.
Simon Iveson, Mayfield, New South Wales, Australia