From Daily Mail:They're those baffling questions that pop into the brain when you've nothing better to think about, and only the appliance of a large helping of science can answer. Now a new book by the experts at New Scientist magazine solves some of the most intriguing queries sent in by readers...
Why does bottled water from a 3,000-year-old source - such as a spring, mountain or glacier - carry a 'best before' date only two years in the future?
The water has passed through layers of rock that have different effects on it. Some minerals dissolve in the water, supposedly improving both its taste and health-giving properties.
The minute pores in the rocks that the water passes through also act as a filtration system, improving purity by removing larger molecules such as biological contaminants. As soon as the pure water emerges from the aquifer it has filtered through, however, it is vulnerable to contamination again.
The 'best before' dates on bottles are based on the amount of time the manufacturer believes the water will remain without measurable levels of contamination due to the lack of completely sterile conditions in their bottling plants.
If the water is stored in a plastic bottle, the date will also relate to contamination from the constituents of the plastic, which may change the taste of the water.
Read more ....
No comments:
Post a Comment