Note: Descriptions are shown in the official language in which they were submitted.
CA 02269833 1999-04-26
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Title
The Use of an Aqueous Chlorite Solution for Disinfection in the Food
Industry
Field of the Invention
This invention relates to the cleaning of equipment and containers,
such as tanks, kegs, bottles and the like, and pipes in the food industry
using an acidic cleaning liquid.
Background of the Invention
At the present time, tanks in the food industry are cleaned by one of
the following methods. After venting or blowing out with air, the tanks are
first prerinsed. They may then be subjected to an alkaline cleaning step in
which they are cleaned with 2% caustic soda solution optionally containing
additives. This cleaning step, which can also be left out, is terminated by
intermediate rinsing. The tanks are then cleaned for 30 to 60 minutes with
an acidic cleaning liquid. The cleaning liquid used contains inorganic or
organic acids. After another intermediate rinse, which lasts about 5
minutes, the tanks are disinfected for about 15 to 20 minutes. However,
the tanks may also be disinfected during the acidic cleaning step, so that
the last of the above-mentioned intermediate rinses and disinfection as
separate cleaning steps can be left out. Finally, in a last step, the tanks
are
rinsed with fresh water for about 10 minutes.
Products based on monobromoacetic acid, peracetic acid, active
chlorine, active oxygen, quaternary ammonium compounds (QUATS) and
other compounds are used for disinfection in modern cleaning and
disinfecting processes applied in the food industry. Unfortunately, none of
the biocides mentioned is satisfactory in every respect. Monobromoacetic
acid is highly toxic. Peracetic acid is not easy to handle and is ineffective
against certain microorganisms. Active chlorine tends to form AOX and,
because of this, is now rarely used. Quaternary ammonium compounds
are attended by the disadvantage of a hydrophobic character.
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In addition, the use of aqueous solutions of chlorine dioxide for
disinfection is known from the prior art (EP 0 489 776 B1). A solution of
chlorine dioxide is prepared by mixing a solution of sodium chlorite and an
acidic component in a separate generator or reactor and is used
immediately afterwards for disinfection. Such generators are known and
are commercially available. Their disadvantage lies in the need for a
separate piece of equipment for preparing the disinfecting solution.
The use of a stabilized, alkalized aqueous chlorite solution for
conditioning water for drinking water purposes and also swimming pool
water and for disinfecting industrial water is known from DE 34 03 631 C2.
If a chlorite solution of this type is added to an aqueous system to be
treated which contains chlorine or mineral acids, chlorine dioxide is mainly
formed. Enzymes of the vegetable and animal metabolism present in the
solution to be treated are spontaneously destroyed by chlorine dioxide. In
contrast to what is said in the patent cited above, chlorine dioxide does not
in fact act with high selectivity, but has an extremely broad action spectrum
by comparison with other biocides.
A significant disadvantage of the known process is that the
disinfecting solution to be added has to be prepared before use from at
least two components, the alkaline solution and the chlorite solution, and
optionally other components.
Summary of the Invention
The problem addressed by the present invention was to enable
disinfection to be carried out in the cleaning process mentioned above
without any need for a separate reactor or to use a disinfecting solution
consisting of several components.
It has now been found that chlorites may advantageously be used
for disinfection in the cleaning of containers and equipment used in the
food industry and the like. If a neutral chlorite solution containing no
additional components is added to the cleaning or rinsing liquid during the
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acidic cleaning step and/or a subsequent rinsing step, excellent disinfection
is achieved in a simple and economic manner. Where the chlorite solution
is added to the rinsing liquid, a sufficiently low pH value is achieved by the
acid still adhering to the equipment and containers or pipes from the
preceding acidic cleaning step. Accordingly, additional acidification is not
necessary. Alternatively, the chlorite solution may also be allowed to act
during the last 10 minutes of the acidic cleaning step. In the process
according to the invention, it is even possible in some cases to dispense
with the final rinsing step if the chlorine dioxide concentration on
completion of disinfection is below 0.2 ppm.
Accordingly, the present invention relates to the use of an aqueous
chlorite solution in the food industry for disinfection during the cleaning of
equipment and containers, such as tanks, kegs, bottles and the like, and
pipes using an acidic cleaning liquid, characterized in that the chlorite
solution is added to the cleaning or rinsing liquid during this cleaning step
and/or a following rinsing step.
More particularly, the invention provides a process for disinfecting
equipment and containers used in the food industry during the cleaning of
such equipment and containers, which comprises adding a chlorite solution
to an acidic cleaning liquid or to a rinsing liquid without pre-acidification,
for
use in a cleaning step and/or to a rinsing liquid for use in a following
rinsing
step.
Alternatively, the invention provides a process of disinfecting
equipment and containers for use in the food industry which involves the
use of an aqueous chlorite solution wherein the process is performed in an
atmosphere containing carbon dioxide, the CO2 leading to acidification of
the water and to the release of CIO2.
Finally, the invention provides an improved cleaning or rinsing
composition for disinfecting equipment and containers used in the food
industry wherein the cleaning composition is acidic and a chlorite solution
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is added to the cleaning or rinsing compositions without prior acidification
for use during the cleaning step and/or in a following rinse step.
One particular advantage of the process according to the invention
is that it is possible to use a neutral chlorite solution without any need for
other components. The low pH value responsible for the release of
chlorine dioxide is established by the acidic solution normally used in any
event for cleaning.
The cleaning or rinsing liquid preferably contains 1 to 1000 ppm of
chlorite and, more preferably, 50 to 400 ppm of chlorite.
Although a solution of sodium chlorite is preferably used, potassium
salts and other salts may also be used.
So far as the action times are concerned, one particular embodiment
of the invention is characterized in that the chlorite-containing cleaning or
rinsing liquid is allowed to act on the containers for at least 20 s and
preferably for 20 s to 20 mins.
The chlorite-containing cleaning or rinsing liquid advantageously has
a temperature of up to 40 C and, preferably, a temperature in the range
from 5 to 30 C.
The pH value of the chlorite-containing cleaning or rinsing liquid
must be below 7 during the disinfecting step and is preferably below 5.
However, there is no need for the additional introduction of acid because
the pH value of the acidic cleaning liquid is sufficiently low and the rinsing
liquid is sufficiently acidified by the residues from the preceding acidic
cleaning step adhering to the containers or equipment or pipes.
In an alternative embodiment of the invention, an aqueous chlorite
solution is used in the food industry for disinfecting equipment and
containers, such as fermentation and storage tanks, in an atmosphere
containing carbon dioxide. Nowadays, fermentation and storage tanks in
breweries are often cleaned in a carbon dioxide atmosphere. In many
cases, the cleaning solution is contaminated to such an extent that the
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necessary disinfection has to be carried out in a separate, following step.
According to the invention, an aqueous solution of sodium chlorite is
pumped through the tanks for this purpose. The carbon dioxide present in
the tank atmosphere acidifies the water so that chlorine dioxide is released.
5 In this case, too, a solution of chlorite in water consisting of only one
component is advantageously used. The other advantage according to the
invention is again achieved, namely that there is no need for a reactor to
release chlorine dioxide.
Example
One example of embodiment of the invention is described in detail in
the following. In this case, sodium chlorite was used for disinfection during
the acidic cleaning of tanks in a brewery.
In a first step, the tank was prerinsed with water for 10 minutes in
order to remove the coarse soil from the inner walls of the tank. The tank
was then cleaned with a 1.5% acidic cleaning solution based on phosphoric
acid. After a cleaning time of about 20 minutes, 10 ppm of sodium chlorite
was added to the acidic cleaning solution. The tank was then disinfected
and cleaned for another 10 minutes.
Finally, the tank was rinsed with fresh water for 10 minutes. A
satisfactory cleaning and disinfection result was obtained.
While the invention has been described with particular reference to certain
embodiments thereof, it will be understood that changes and modifications
may be made by those of ordinary skill in the art within the scope and spirit
of
the following claims.
In the claims, the word "comprising" means "including the following
elements (in the body), but not excluding others"; the phrase "consisting of'
means "excluding more than traces of other than the recited ingredients";
and the phrase "consisting essentially of' means "excluding unspecified
ingredients which materially affect the basic characteristics of the
composition".
