Introduction
Bottled water is produced and distributed as a packaged food product and
listed under food standards legislation in the UK. The larger bottles seen on water dispensers
in offices and other locations are a popular means of providing hydration to
work forces in many industries and students in schools and universities.
Production, Storage and Distribution
The large 19L bottles are filled in a bottling plant and transported to
distribution depots where they are stored for a while before delivery to
customers. When the bottles are empty,
they are collected from the customer, returned to the distribution depot and
subsequently forwarded to the bottling plant for washing and refilling.
Choice of Polycarbonate
Polycarbonate is the major plastic material used for the large 19L
bottles. This has many advantages over
other plastic materials, for example, it is a clear, strong plastic which is
durable and able to withstand the washing process at high temperatures without
shrinkage or damage. The disadvantage of
polycarbonate is the porosity of the material when used in bottles. Although the porosity does not affect any of
the other bottle properties, there is a vulnerability to transmission of
certain materials through the bottle walls which can then affect the taste of
the water. The porosity of polycarbonate
has been studied and several scientific papers are available1, 2. The taste buds are very sensitive to minute
traces of odoriferous materials in water.
Airborne Contaminants Affecting Taste
Materials with a strong odour, such as solvents, strongly flavoured
foodstuffs such as garlic and coffee and certain chemicals will all affect the
taste of water if kept in close proximity.
Of particular concern are highly volatile materials, such as volatile
organic compounds, since the concentration of these can be very high near their
source. Small molecules are able to
penetrate through polycarbonate more easily than larger molecules, for example,
xylene is both volatile and a small molecule.
This is a component of paints and other coatings.
Proximity of Contaminants
It is a requirement of all distribution depots that no materials
affecting the taste of water are allowed within the depot. For example, diesel fork lift trucks are
forbidden. It is necessary at certain
times of the day to open the roller doors to allow access for loading and
unloading. At this time, the bottled
water is vulnerable to contaminants coming from the immediate outside
environment. This is particularly a
problem with volatile contaminants such as solvents and other chemicals. The choice of location of the depot is made
with due consideration of near neighbours and any existing processes which
could result in airborne contamination.
This sometimes limits the choice of location.
At the point where the roller doors are open, prevailing winds, down
draughts, humidity or rain can markedly affect the ingress of contaminants that
could affect water taste.
References
- D. S. Lee, K. L. Yam and L. Piergiovanni
“Food Packaging Science and Technology”, CRC Press, Taylor and Francis
Group (2008).
- Valentina Siracusa “Food Packaging
Permeability Behaviour: A Report” International Journal of Polymer
Science, 2012 (2012) Article ID 302029, 11 pages.
