Chlorination of
domestic, public and private water supplies has been used since the early
1900s to safeguard against water-borne diseases. In recent years, chlorination
of industrial water has become a common practice
in food processing plants as a means of improving plant sanitation. Chlorination
can include the use of chlorine gas, hypochlorites or chloramines.
When used in a food processing plant, chlorine must be applied under controlled
conditions if the desired germicidal effects are to be obtained without
adverse results. Moreover, chemical and physical characteristics of the
water – such as average pH, temperature, chlorine demand, concentration
of organic matter, volume and the presence of phenols or other materials
which might affect flavors– must be known in order to ensure
the effective and efficient use of chlorine disinfection.
Regardless of the type of chlorine compound used for disinfection, free
chlorine residuals of 4-7 parts per million (ppm) at the point of water
application to equipment are recommended. If the operations are light (e.g.,
only one shift), satisfactory control may be maintained with lower
concentrations, whereas during heavy operation 5 ppm may be required. An
increase to chlorine
residuals of 10-20 ppm is recommended for cleanup purposes. This serves
to give an effective germicidal treatment to all equipment in the plant.
The chlorination of water in food processing plants could potentially affect
food quality and the can or plant equipment. Research performed by the
National Canners Association on the effects of chlorine on the flavor of
29 fruits and vegetables shows that a few items – apples, pears,
cling peaches, figs, strawberries and yams – are the most susceptible
to chlorine flavor. Testing further showed that a chlorine concentration
of 5 ppm has no effect on the color or ascorbic acid content.
While corrosion attributable to chlorination is not normally a problem
in food processing applications, its possibility should not be ignored.
Chlorine can be corrosive to common metals such as brass, aluminum and
steel. However, research and field experience has shown that in low concentrations
(2-5 ppm) it does not noticeably corrode either the cans or equipment.
In fact, even at high concentrations (10-20 ppm) typically used for clean-up,
chlorine does not produce significant corrosion because the contact time
is too short. Moreover, corrosion is most severe in conditions where slime
deposits exist, and the use of chlorine helps prevent slime formation.
For in-plant chlorination to be most effective there should be a continuous
application of chlorinated water to all surfaces where bacteria are likely
to grow and slime to form. This may involve additional piping. For belts,
bucket elevators, reel washers and similar equipment, the chlorine may
be applied by installing sprays of chlorinated water in such a way that
they will constantly bathe the moving surfaces. Best results are obtained
on belts when the chlorinated water is sprayed on both sides of the belt.
For equipment such as fillers, dicers and peelers where a continuous application
of chlorinated water is not possible, water lines with short hoses should
be installed near each machine to be used for washing the equipment each
time operations cease. As a precaution against off flavors, it is advisable
to install lines of unchlorinated water for syrup or brine making, for
boiler water and for drinking purposes.
Regardless of the source of chlorine, only automatic equipment that feeds
the chlorine in proportion to the water flow should be used. This is necessary
to avoid fluctuations in the chlorine level, that if too low would be
ineffective, or if too high might produce off flavors and corrosion.
After the installation of the chlorine disinfection system has been made
it should be turned on for at least a week before canning operations are
commenced to “burn out” all organic matter in the lines. This
will help eliminate chances of off flavor and will reduce the potential
of employee objections to unpleasant odors. It is recommended that an experimental
pack using the chlorinated water should be made prior to the start of operations
to determine the possibility of off flavor. All cresols, phenols or phenol-like
compounds should be removed from the plant because chlorine in combination
with such materials produces compounds that have a very strong flavor even
when present in minute quantities. Material that may contain phenols and
cresols include marking inks, paints, fly sprays, special wood sealers,
hand lotions and boiler feed water compounds.
Continuous laboratory control is essential for safe application of in-plant
chlorination, and the following schedule is recommended:
- Check the
chlorine residual every two hours to help establish the variations
likely to be encountered.
- After the first week, check the chlorine residual at several
points in the plant at least twice a day, sampling the same
places each day. Sample should
be taken from a tap that has been running for several minutes.
- Record all residuals observed and taste the water (if potable)
every time a residual is taken as a check on possible off flavors.
- Record the chlorinator setting each time the residual is
taken.
- Weigh the chlorine cylinder each day at the same time, and
record the loss in weight to ensure the accuracy of the chlorinator
feed setting and
to determine when a new cylinder is needed.
- Check the chlorinator operations, and at least once a day
inspect for leaks using an ammonia bottle.
For more information, contact Severn
Trent Services at info@severntrentservices.com.