Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Cleaning method for machine dishwashing
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Technical field of the invention
This invention relates generally to the field of machine
dishwashing processes, e.g. for cleaning tableware or
other surfaces soiled with food remains. More particular
this invention relates to field of continuous or
discontinuous machine dishwashing processes in single or
multi-tank dish machines.
Background of the invention
In conventional dishwashing processes, may it be
continuous or discontinuous, elevated temperatures are
used which are commonly regarded as elementary,
especially for satisfying the hygiene requirements in
view of the microbiology. In Germany, the DIN 10510 (multi
tank machine) and the DIN 10512 (single tank machine)
advise a minimum temperature within the wash tank of
60 C to 65 C when using detergents without disinfection
components. For the final cleaning step a minimum
temperature of 80 C to 85 C is recommended. The overall
contact time of the dishes should not be shorter than 120
seconds (multi tank) or 90 sec (single tank)
respectively.
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One the other hand, dishwashing processes which require
lower temperatures are advantageous for ecological as
well as economical reasons. Furthermore the stress for
the tableware or other goods to be cleaned decreases with
the temperature which these goods are exposed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a
dishwashing process in which lower temperatures can be
used while satisfying hygiene requirements.
This object is solved by a process according to Claim 1.
Accordingly, a process for continuous or discontinuous
machine dishwashing is provided, comprising the steps of
a) Applying a first basic cleaning step whereby the
cleaning solution has a pH of 10,5
and 13 at a
temperature of 30 and 55 C.
b) Applying an acidic cleaning step whereby the cleaning
solution has a pH of 1 and 3 at a temperature of 50
and 75 C.
c) Applying a second basic cleaning step whereby the
cleaning solution has a pH of 10,5 and 13 at
a
temperature of 30 and 55 C.
d) Applying a rinse step, whereby the cleaning solution
has a pH of 5 and 7 at a temperature of 50 and 75 C.
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Surprisingly it has been found that such a process has
for a wide range of applications within the present
invention at least one of the following advantages:
- By using this process it is possible to reach a
satisfying cleaning result as well as meeting
hygienic standards while avoiding high temperatures
(especially temperatures over 75 C)
- By avoiding these high temperatures, a significant
amount of energy can be saved
- Lower temperatures lead to a lower environmental
footprint of the wastewater
According to a preferred embodiment of the invention,
step a) and/or step c) is performed at a temperature of
40 and 50 C, preferably around 45 C.
According to a preferred embodiment of the invention,
step b) and/or step d) is performed at a temperature of
55 and 70 C, preferably between 60 and 65 C and most
preferred around 63 C.
According to a preferred embodiment of the invention in
step a) and/or c) the cleaning solution has a pH of 11
and 12.
According to a preferred embodiment of the invention in
step b) the cleaning solution has a pH of 2 and 2,5.
According to a preferred embodiment of the invention,
step a) is performed for 10s and 60s.
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According to a preferred embodiment of the invention,
step b) is performed for 10s and 20s.
According to a preferred embodiment of the invention,
step c) is performed for 20s and 60s.
According to a preferred embodiment of the invention,
step d) is performed for 5s and 15s.
In the following the four steps of the invention are
described in more detail:
Step a): First alkaline cleaning step
Step a) is the first alkaline cleaning step in the
context of the invention and is performed using a
cleaning solution having a pH of 10,5 and 13,
preferably 11 and 12. This pH can be achieved e.g. by
using hydroxide solution and/or hydroxide/buffer
solution, especially hydroxide/ phosphate buffer solution
Furthermore the cleaning solution used in step a) may
include one or more of the following ingredients:
¨ Complexing agents, Chelants, Builders
¨ Surfactants
¨ Corrosion inhibitors
¨ Processing additives
The cleaning solution is sprayed onto the tableware
trough a rotating washing arm as a heavy water curtain.
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Step a) is performed at a temperature of 30 and 55 C,
which means that the cleaning solution which is applied
to the tableware has this temperature. More preferred,
step a) is performed at a temperature of 40 and 50 C,
preferably around 45 C
Step a) preferably is performed for 10s and 60s, more
preferred for 20s and 30s. However, it should be noted
that the duration of step a) is not limiting for the
invention, only for some preferred applications within
the same.
Step b): Acidic cleaning step
Step b) is the acidic cleaning step in the context of the
invention and is performed using a cleaning solution
having a pH of 1 and 3, preferably 2 and 2,5 This pH
can be achieved e.g. by using an inorganic or organic
acid.
Suitable acidic compounds in the context of this
invention which are insofar preferred are sulfuric acid,
nitric acid, phosphoric acid, formic acid, acetic acid,
propanoic acid, glycolic acid, citric acid, maleic acid,
lactic acid, gluconic acid, alkanesulfonic acid,
amidosulfonic acid, succinic acid, glutaric acid, adipic
acid, phosphonic acids, polyacrylic acids or mixtures
thereof and, in a most particularly embodiment, from
formic acid, glycolic acid, gluconic acid, amidosulfonic
acid or the alkanesulfonic acids, more particularly
methanesulfonic acid or mixtures thereof. Especially
preferred is methanesulfonic acid.
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Furthermore the cleaning solution used in step b) may
include one or more of the following ingredients:
¨ Surfactants
¨ Hydrotropes
¨ Stabilizer
¨ Processing additives
In a preferred embodiment of the process according to the
invention, the cleaning solution is allowed to act on the
tableware and the soil for a certain contact time (during
which spraying stops).
In another preferred embodiment, the tableware is not
intentionally sprayed during the contact time.
Alternatively or additionally, the cleaning solution is
sprayed onto the tableware as a fine, gentle mist-like
liquid spray.
Alternatively or additionally, the cleaning solution is
applied to the tableware as foam.
Alternatively or additionally, the cleaning solution is
applied to the tableware in droplet form or by the Ecolab
process known commercially as thin film cleaning (TFC).
Step b) is performed at a temperature of 50 and 75 C,
which means that the cleaning solution which is applied
to the tableware has this temperature. More preferred,
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step b) is performed at a temperature of 60 and 65 C
and most preferred around 63 C
Step b) preferably is performed for 11)s and 20s.
However, it should be noted that the duration of step b)
is not limiting for the invention, only for some
preferred applications within the same.
Step c): Second alkaline cleaning step
Step c) is the second alkaline cleaning step in the
context of the invention and is performed using a
cleaning solution having a pH of 10,5 and 13,
preferably 11 and 12. This pH can be achieved e.g. by
using hydroxide solution and/or hydroxide/buffer
solution, especially hydroxide/ phosphate buffer solution
Furthermore the cleaning solution used in step a) may
include one or more of the following ingredients:
¨ Complexing agents, Chelants, Builders
¨ Surfactants
¨ Corrosion inhibitors
¨ Processing additives
The cleaning solution is sprayed onto the tableware
trough a rotating washing arm as a heavy water curtain.
Step c) is performed at a temperature of 30 and 55 C,
which means that the cleaning solution which is applied
to the tableware has this temperature. More preferred,
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s t ep c) is performed at a temperature of 40 and 50 C,
preferably around 45 C
Step c) preferably is performed for 20s and 60s, more
preferred 45s and 55s. However, it should be noted that
the duration of step c) is not limiting for the
invention, only for some preferred applications within
the same.
Step d): Rinsing step
Step d) is the neutral rinsing step in the context of the
invention and is performed using a rinse aid solution
having a pH of 5 and 7.
The rinse aid solution used in step d) may include one or
more of the following ingredients:
¨ Surfactants
¨ Organic and/or inorganic acids
¨ Auxiliaries
¨ Hydrotropes
¨ Processing additives
In a preferred embodiment of the process according to the
invention, the cleaning solution is allowed to act on the
tableware and the soil for a certain contact time (during
which spraying stops), as it step d) usually is the last
step in the dishwashing cycle.
In another preferred embodiment, the tableware is not
intentionally sprayed during the contact time.
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Step d) is performed at a temperature of 50 and 75 C,
which means that the cleaning solution which is applied
to the tableware has this temperature. More preferred,
step b) is performed at a temperature of 60 and 65 C
and most preferred around 63 C
Step d) preferably is performed for 5s and 15s,
preferably 9s and 12s. However, it should be noted that
the duration of step d) is not limiting for the
invention, only for some preferred applications within
the same.
The afore mentioned components, as well as the claimed
components and the components to be used in accordance
with the invention in the described embodiments, are not
subject to any special exceptions with respect to their
size, shape, material selection and technical concept
such that the selection criteria known in the pursuant
field can be applied without a limitation.
BRIEF DESCRIPTION OF THE EXAMPLES
Additional details, features, characteristics and
advantages of the object of the invention are disclosed
in the following description of the examples, which - in
exemplary fashion - show several embodiments and examples
of a process according to the invention. The examples are
to be understood merely to further illustrate the
invention and are not binding.
Example I
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Cleaning of table cups and table plates in a MEIKO DV80.2
dishwashing machine sold by Meiko company, Offenburg,
Germany.
For each test, 3 dry, clean table cups were soiled by
being dipped in a coffee and milk brew at 70 C for 25
times (1 min in the solution followed by 1 min drying
each dipping cycle) and afterwards dried for 2 hours at
90 C according to a standardized test protocol.
Furthermore for each test 3 dry, clean table cups were
dipped in a black tea and milk brew at 70 C for 25 times
(1 min in the solution followed by 1 min drying each
dipping cycle) and afterwards dried for 2 hours at 90 C
according to a standardized test protocol.
Finally for each test three plates soiled with starch at
room temperature by a standardized test method.
To this end, a ca. 6% aqueous composition containing corn
starch was cooled to 75 C after boiling and was applied
to each cup with a brush in a quantity of ca. 4 ml. The
cups thus treated were left to stand for at least 3 hours
and then dried at ca. 100 C for 16 hours.
The cleaning tests were carried out in a Meiko DV80.2
hood-type dishwashing machine according to the following
scheme:
a) Cleaning for 25 seconds at a temperature of 45 C with
a 0.2% by weight aqueous solution of an alkaline
detergent, the solution having a pH of 12.
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b) Cleaning for 5 seconds at a temperature of 63 C with
a 0.2% by weight aqueous solution of an acidic detergent,
the solution having a pH of 2.5.
c) Cleaning for 49 s seconds at a temperature of 45 C
with a 0.2% by weight aqueous solution of an alkaline
detergent, the solution having a pH of 12.
d) Rinsing for 12 seconds at a temperature of 63 C with
fresh water
The cleaning was evaluated by scoring on a scale of 1 (=
no visible sign of cleaning) to 10 (= complete removal of
soil), resulting in a score of 8.
EXAMPLE II
Example II is identical with Example I, only that an
Electrolux "Clean and Green" WT65 dishwashing machine,
sold by Electrolux company, Stockholm, Sweden was used.
The cleaning resulted in a score of 9.
The particular combinations of elements and features in
the above detailed embodiments are exemplary only; the
interchanging and substitution of these teachings with
other teachings in this and the patents/applications
incorporate by referency are also expressly contemplated.
As those skilled in the art will recognize, variations,
modifications, and other implementations of what is
described herein can occur to those of ordinary skill in
the art without departing from the spirit and the scope
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of the invention as claimed. Accordingly, the foregoing
description is by the way of example only and is not
intending as limiting. In the claims, the wording
"comprising" does not exclude other elements or steps,
and the identified article "a" or "an" does not exclude a
plurality. The mere fact that certain measures are
recited in mutually different dependent claims does not
indicate that a combination of these measures can not be
used to advantage. The inventions scope is defined in the
following claims and the equivalents thereto.
Furthermore, reference signs used in the description and
claims do not limit the scope of the invention as
claimed.
