Note: Descriptions are shown in the official language in which they were submitted.
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lhe p~cse~t invel)~it)n rcla~es ~n thc saniti-,in~, a~ld
s~crilizin~ of the sur~aces of objects and, more particularly~ to
~ ~ys~em and me~noa ror als mrcc~ln~ D~cLeri~ iaaen surrac~s DY
spraying the objects wi~h a sanitizing solution.
In ~ood processing plants, bottling plants, dairies
and the like, it is a constant requirement that sanitary condi-
tions be maintained. One important sanitizing requirement is the
disinfecting of the surfaces of physical objects about the plant
by the use of bactericidal sanitizing methods. Tlle systems and
methods which must be employed, particularly in food processing
installations, must be safe and ~on-toxic when they are being
used, and also must be safe and l~on-toxic in storage prior to
use, and must furthermore leave no unsafe or toxic resins.
Several bactericidal nlethods have been ernployed in the
prior art, One common method of ~he prior art is to wash all
physical objects including walls and major items of.equipmen~
with a bactericidal solution containing bactericidal substances
such as quaternary ammonia or chlorine. Chlorine solutions, for
; example, have been found to be fairly efective in killing bacteri a
in such cases. However, low p~ chlorine solutions which are the
most effective bactericides are so highly unstable and have such
a limited shelf life that the storage and use of them as effectiv~
bactericid~s has heretofore been highly impractical. ~igh pH
. solutions, on the other hand, in which chlorine is largely in
the form of sodium or calcium hypochlorite, have a somewhat
longer shelf life, but are less effective bactericides than the
1(~74~2
low pH solutions in which the chlorine is largely in the form of ~ypochlorous
acid. To maintain high pH solutions in which the chlorine is in the more
stable form, it is necessary that additives such as sodium hydroxide be added
to the solution Such additives, in addition to decreasing the bactericidal
effectiveness of the solution, create an additional hazard in that a toxic
and irritative solution is formed which leaves a toxic and irritative residue
on the surfaces which are washed with the solution and requires that the
subsequent washing of these surfaces be undertaken in order to remove this
residue. Other additives, for example some used as stabilizers for calcium
hypochlorite, form dangerously flammable compounds if not handled or stored
properly. Since the most practical way of disinfecting the facilities in the
food processing industry has been to wash the facility with the spray of the
disinfecting solution, which solution has been purchased in bottle form and
stored for at least a short period of time or premixed prior to use from
powdered chemicals, these disadvantages have been inherent when such dis-
infecting methods have been used in the prior art.
The present invention overcomes the disadvantages of the prior art
by utilizing the high bactericidal effectiveness of relatively low pH
chlorine solutions while avoiding the problems inherent in storing and
preserving the solution prior to use, and while eliminating the toxic
irritating and hazardous effects of certain solution additives.
The present invention provides a method and apparatus for contin-
uously generating a bactericidal solution in which the predominant bacteri-
cidal constituent is hypochlorous acid. To this end the invention contemplates
the formation of a brine solution to which an acid, preferably acetic acid,
and water are added so that the resultant solution has a pH of approximately
6. That solution, when immediately electrolyzed, results in the production
of chlorine in a bactericidal form of which 95-98% is hypochlorous acid.
According to one aspect of the invention there is provided a method
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for producing the method of creating a bactericidal solution compris mg the
steps of; mixing sodium cnloride, an acid and sufficient waber to prcvide
a solution having a pH of approximately 6, and electrolyzing the solution to
generate nascent chlorine ~hich is mainly in the form of hypochlorous acid.
The lcwering of the pH of the solution to approxlmately 6 is
extremely im~ortant to the efficacy of the subsequently electrolyzed solution.
The following table illustrates the dramatic change in the ratio of hypcchlor-
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074Z~Z
ous acid to other and less efficacious chlorine containing constituents: -
pH Value% available CL2 in the form of Hypochlorous Acid
at 6.o98% of total free CL2
;~ up to 6.795% of total free CL2
at 7.080% of total free CL2
at 8.o21% of total free CL2
at g.o2.7% of total free CL2
at 10 0.3% of total free CL2
While the lowering of the pH below 6 does not adversely affect the cidal
prop0rties of the solution, the solution tends to become ~uite corrosive and
hence less desirable.
Further, it has been determined that low pH nascent chlorine~ in
the form of hypochlorous acid, is up to three times as effective or has three
times the killlrate of nascent chlorine as a hypochlorite.
Also disclosed herein is a method and apparatus for continuously
forming the desired low pH cidal solution, including the supplying of metered
amounts of glacial acetic acid to a brine solution and mixing the resultant
solution with metered amounts of water to form the solution to be electrolyzed
In the process it is contemplated that the amount of acetic acid in relation
to the other constituents will have to be varied to account for differing
pH of the incoming tap water normally employed in the process.
Further, there is disclosed an industrial system and method for
disinfecting the surfaces of objects, particularly in food plants and other
areas where high bactericidal effectiveness is required but where toxicity
must be completely avoided. The problems of the prior art are overcome by
providing a disinfecting system in which a continuous stream of bactericidal
; sanitizing liquid is sprayed upon objects to be disinfected, and in which the
bactericidal effect of the sanitizing solution is enhanced by generating
nascent or instant chlorine in a relatively low pH solution, immediately
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before the solution is sprayed upon the objects which are to be disinfected.
By generating this nascent chlorine in a relatively low pH solution, in its
most effective but least stable form, and then spraying it in a continuous
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washing stream directly upon the surfaces of objects to be disinfected
immediately after the
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solution is generated, and before the solution is able to deteriorate
to a less effective level, results in a greatly increased bactericidal
effectiveness over the systems and methods of the prior art.
In addition to the high bactericidal effecti~eness of the
present invention over the prior art, and the advantages provided in
the reduced toxicity and irritability to living tissue which the present
invention provides, it has been found that the materials required cost
only a small fraction of the cost of materials used in common methods
of the prior art.
There are several other advantages which the present invention
provides, particularly when compared with systems of the prior art
in which the high pH hypochlorite solution is maintained by the addition
of, for example, caustic lye. Nascent chlorine solutions can be detected
by smell only at concentrations that are many times higher than the
concentrations of these prior art solutions. The same applies to detection
by taste. Furthermore, the stable hypochlorite solutions will irritate
the eyes and will bleach certain colors at far lower concentrations
than will nascent chlorine.
Purthermore, the nascent chlorine is believed to be far superior
to the stable hypochlorite solution in its ability to eliminate odors.
While prior art systems have been devised for utilizing the
electrolytic generation of chlorine for disinfecting and sanitizing
purposes, the advantages of utilizing nascent electrolytically generated
chlorine for a spray solution, in industrially usable quantities, to
sanitize the surfaces of objects has not been realized or appreciated.
For example, electrolytic chlorine systems ha~e been proposed for disinfecting
a fluid or water supply by electrolytically generating chlorine in
the solution which is to be disinfected to kill bacteria carried by
the fluid. One such application has been in the swimming pool disinfecting
area. Another application has been in deodorizing air, an area in
which the decomposition and deterioration of the solution in which
the chlorine is generated results in a dispersing of the bactericidal
-"` 1074252 :~
chlorine into the atmosphere which is to be disinfected.
The present invention, unlike the systems of the prior art,
enables bringing the chlorinated solution, while in its most effective
bactericidal form, on~o the surfaces of objects to more effectively
and completely disinfect the objects than has heretofore been realized,
while maintaining greater safety but far lower toxicity and at a lower
cost than has been realized in the prior art.
More specifically, it has been an objective of the invention
to provide a process for disinfecting meat carcasses by spraying or
washing the carcass with the low pH solution of the present invention
at a concentration from twenty-five to about two hundred parts per
million.
In the meat processing industry, the meat carcass after slaughtering
is highly contaminated on its surface with bacteria. Surface contamination
has a considerable shelf life shortening effect on the meat, for in
the cutting of the meat into its component parts and grinding into
ground beef and the like, the surface bacteria are driven from the
surface of the meat into interior portions of the meat where they multiply
resulting in early spoilage of the meat. Numbers of attempts to solve
this problem have been made but have been ineffective. Of the attempts
made, perhaps the one which approaches a practical process is that
of washiDg the meat carcass with a commercial high pH hypochlorite
of the type described above. This process, however, has been effective
in eliminating only 90% of the bacteria. The remaining 10%, having
the capability of migrating or being forced onto interior surfaces
of the meat and having the capability of multiplying under conditions
of storage, still give rise to demonstrable spoilage. It has been
found that by washing the surface of the meat with the solution produced
in accordance with the present invention, the bacteria are entirely
or substantially entirely eliminated from the surface of the meat;
that is to say, the resulting bacteria are too few to count, indicating
that ~he process is at least 9g.99% effective.
`-` 1074~SZ
These and o~her objectives and advantages of the pr~sen~
invention ~ill be more readily apparent from the following detailed
description of the drawings illustrating an electrolytic spray sanitizing
system and method according to principles of the present invention.
Figure 1 is a hybrid block, plumbing, and schematic diagram
of an electrolytic spray sanitizing system embodying principles of
the present invention.
Figure 2 is a perspective view of a portable unit housing
the disinfecting solution generating components, and of the portable
wand of the system of Figure 1.
Figure 3 is a cross-sectional view of an electrolytic cell
suitable for use in the system of Figure 1.
Referring to Figure 1, one preferred embodiment of a system
according to the present invention operates to spray a sanitizing liquid
in the form of a continuous spray 1~ directly upon the bacteria laden
surfaces of objects to be disinfected, such as the walls and floors
` of the building structure 11 in, for example, food processing plants
.~ and the like, or upon the surfaces of other objects 12 such as machinery,
furniture, or other equipment in such facilities.
The sanitizing system includes two independently movable
parts which can be better seen by reference to Figure 2. These parts
are the portable sanitizing solution generating unit 20 and the spray
wand 30. The unit 20 includes a high grade stainless steel cabinet
21 mounted on casters 22 so that it can be rolled freely about a plant.
: Mounted on the front of the unit 20 are a power on-off switch 23, a
power on indicator light 24, a chlorine solution output meter 25, and
an operating instruction plate 26, all arranged on an operator panel
27. The unit 20 also includes a power line cord 28 which is connectable
either to a 220 volt AC or a 110 volt AC power line, depending on the
internal wiring of the unit 20.
The unit is provited with a fluid inlet port 29 connectable
to a conventional tap water outlet of cold water, preferably supplied
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at a pressure of from 40 to 65 psi. T~e unit is further
provided with two outlet ports for dispensing sanitizing
fluids. These ports include a primary outlet port 31 and
a bulk outlet port 33. When the system is operating according
to principles of ~he present invention, sanitizing solution
will be emitted through the primary outlet port 31 and conducsed
through a hose 32 to the wand inlet port 35.
The unit 20 is also provided with an electri al
connector 36 which connects through a control cable 37 to
a trigger toggle switch 38 carried by the want 30. The switch
38 provides a means for cont~olling operation of the generator
unit 20 from the hand held want 30 to selectively control -
the output of spray solution. The switch 38 is a three-position
switch having an "OFF" position, a "sanitizing solution ON"
position which causes the generation of sanitizing solution
and the pumping of the solution to the wand 30, and a "flush
ON" position in which unchlorinatèd water is communicated
through the central unit and to the wand to flush the system.
The wand 30 is provided with a pistol grip-type
handle 41, a fluid discharge nozzle 42, and a rigid tubular
contuit 43 which communicates fluid from the wand inlet poTt
35 to the nozzle 42.
Referring again to Figure 1, the internal and operative
details of the wand assembly 30 and the central unit 20 are
; illustrated. The central unit 20 includes two basic sub-
systems. the solution generating or fluid handling sub-system
50, and the electrical control system 110.
The solution generating system 50 includes a brine
tank 52 in which a saline solution is prepared. This tank
has a removable lid 53 fastened to the tank 52 by bolts 54.
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10742~
The lid 53 is removable so that salt 55 can be daposited
in the tank, and so that the tank can be cleaned periodically.
A level of water 56 is maintained in the tank 52 and the
quantity of salt 55 is maintained at such a level that
a saturated saline solution is formed in the water 56.
The tank 55 is provided with an outlet pipe 57 which connects
to the input of a positive displacement pump 58 which is
driven by a motor 59. The pump 58 is a diaphragm type
pump having a variable displacement which is controlled
by a cam on the drive shaft 61 of the motor 59. The outlet
of the pump 58 is connected through a check valve 62 to
a "T" 63 which has an outlet connected to the inlet 66
at the bottom of the electrolytic cell 70.
The apparatus includes a system for supplying
metered amounts of acid, preferably 85% glacial acetic
acid, into the saline solution to lower its pH. If the
tap water and hence the saline solution is at a pH of 7,
then 2 oz. of acid for each gallon of water are required
to achieve the desired pH level.
The acid is contained in a supply 75 connected
through a line 76 which includes a pump 77 to the tank
52. Tank 52 is also supplied with fresh make-up water
from the inlet port 29 via a line 78 which contains a throttle
valve 79 and a flow switch 80. A float valve 81 connected
to the line 78 detects the demand for additional solution
as, for example, when the solution level drops by two gallons
ant permits water from the port 29 to flow through line
78 to the tank 52. The throttle val~e is set to meter
the fresh water at two gallons per minute.
The flow of water closes switch 80 causing pump
77 to operate to supply acid to the tank. The pump has
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a variable setting permitting the operator to meter the
flow of acid to the tank in accordance with the flow of
water and its pH. For example, if the water is at 7 pH,
she pump would be set for 4 oz. per minute ~o result in
2 oz. of acid per gallon of make-up solution.
The clear water inlet 29 of the unit 20 is also
connected through a solenoid controlled check valve 71
operated by a solenoid 72 and through a manually controlled
needle valve 73 ant a check valve 74 to the other input
of the "T" 63. At the "T" 63, clear water from the input
29 is mixed with the saline solution from the tank 52 in
. ratios which are controlled by the combined settings of
the cam on the pump motor input shaft 61 and the needle
valve 73.
The combined solution enters the cell 70 at the .
.. cell input 66 and flows upwardly through the cell where
the solution is chlorinated in a conventional manner in
; which the electrolytic reaction causes chlorine gas to
be formed and to combine with the other constituents of
the solution to form principally hypochlorous acid (HOCl),
certain other compounds such as sodium hypochlorite (NaOCl),
: and certain active free radicals, along with other byproducts
of the reaction. The chlorinated solution, now at a p~l -
of 6 - 0.1, is emitted from the cell 70 at the outlet 69,
into a "T" 68. The "T" 68 provides alternative outlets
for the solution from the cell through a pair of manually
controlled gate valves 64 and 65. The valve 65 controls
the emission of bulk solution at the outlet 33 of the unit
20 in the event that it is wanted for use in sanitizing
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processes other than the spraying of physical objects.
The gate valve 64 controls solution to the outlet 31 which -~
connects to the hose 32 to communicate the electrolytically
generated chlorinated sanitizing solution to the wand 30.
This solution, when flowing, enters the wand 30 at the
inlet 35 and is communicated through $he tube 43 to the
nozzle 42. All fluid fittings of the system are preferably
constructed of either polyvinyl chloride or stainless steel
to insure high corrosion resistance.
The details of the cell 70 will be better understood
by reference to Figure 3. The cell 70 includes a cylindrical
cell body 67 made of a non-corrosive metal or other non-
corrosive material. The body is provided with an inlet
66 at the bottom ent 82 thereof and, at its upper end,
is providet with a flange 83. The cell head 85, made of
electrically non-conductive material, is secured tightly
to the top of the flange 83 by bolts 87 in such a way as
to seal the interior 86 of the cell 70. The upper
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surface of the flange carries an O-ring 90 to effect a seal between the head
85 and the cell body 67. The cell head 85 is provided with an outlet passage
89 which communicates between an interior opening 88 at the center of the
cell head 85 at a point between the electrodes and the cell outlet port 69.
The cell 70 is provided with a pair of electrodes including an
anode assembly 91 and a cathode assembly 92. The anode 91 is preferably
constructed of a noble metal material such as platinum or platinum alloy. It
may be constructed either of a solid noble metal alloy or consist of a noble
metal plated or larninated material. Other materials may also be suitable
. ~, .
for some applications such as carbon or lead dioxide. Each type has certain
disadvantages; the preferred noble metal anodes, while the most desirable,
are the most expensive. Carbon anodes deteriorate rapidly to the point of
adversely affecting the efficiency of the cell. Lead dioxide is moderately
acceptable but it must be insured that the lead does not contaminate food
; processing or other like areas. The cathode 92 need not be constructed of
a noble metal but should be constructed of a non-corrosive material. Several
commercially available titanium and nickel alloys are suitable for this
purpose. The electrode assemblies 91 and 92 include the lower immersible
portions 93 and upper support portions 94 which extend through the cell head
85. The support portions 94 are adapted to secure the electrodes 91 and 92
to the cell head 85 and are provided with threaded ends
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by which they may be tightened to the head 85 through the use of the
nut and washer assemblies 96. A6Ove the nut and washer assemblies
96 on the electrode support portions 94 are provided other means,
such as additional nuts and washers 97, to enable the electrodés to
be connected to appropriate wire conductors. A pair of tapered neoprene
washers 99 surround the support portions 94 beneath the nut and washer
assemblies 96 to form seals between the supports 94 and the head 85.
The electrodes are supported at their lower portions 93
by two pairs of polyvinyl chloride spacers 102 which surround nylon
bolts 101. Attached to the lower end of one of the electrodes is
a baffle member made of an acrylic plastic 104 which is provided in
order to prevent the pulsating saline solution which enters the chamber
from port 66 from spurting between the electrodes 91 and 92 and cyclically
varying the electrical properties of the condensing solution. Such
spurting causes a pulsating current flow through the cell and renders
the cell operation difficult to monitor and regulate. By providing
the baffle 104, a more uniform and homogenous solution is maintained
within the cell cavity 86. This also causes a more uniform electrolyzing
current to flow between the electrodes by reducing the pulsating change
with time of the properties of the solution between the electrodes.
To direct the solution along an axial path between the electrodes,
a pair of non-conductive plates 105 extend between each of the opposite
edges of the electrodes from their tops to approximately one-half
inch from their bottom ends. The plates 105 are preferably transparent
to facilitate inspection.
Referring again to Figure 1, the electrical control circuit
110 includes a power supply which connects to the AC line 28 through
a paiT of fuses 112 and the on/off switch 23 located on the panel
27. The switch 23 is a double-pole single-throw switch which connects
either 110 or 220 volt AC power to the unit line voltage lines 113
and 114. The lines 113 and 114 are connected across the primary winding
115 of a step-down transformer 116 which has a 24 volt secondary winding
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1~74;Z5Z
117. A power "ON" indicator light 24 is connected across the winding
117. One of the terminals 121 of the transformer secondary winding
117 is connected to the wiper contact 122 of the wand tTigger switch
38 through the cable 37. The switch 38 is also provided with a normally-
opened OFF contact 124 and two contacts 125 and 126, which are connected
through relay windings 131 and 132 respectively to the other secondary
terminal 118 of the transformer 116.
The relay 131 is actuated when the trigger switch 38 is
in the flush position 125. This relay 131 operates relay contact
set 131-1 which connects the solenoid winding 72 across the AC lines
113 and 114. Similarly, a contact set 132-1 is connected in parallel
across the contacts 131-1 to similarly energize the solenoid 72 when
the switch 38 is in the sanitizing position. A second set of contacts
132-2 of the relay 132 operates, when the switch 38 is in the sanitize
position, to connect the winding of the motor 59 across the lines
113 and 114. Connected across the motor winding leads 142 is the
primary winding 144 of a transformer 145. The transformer 145 is
a step-down transformer having an approximately 20 volt output secondary
winding 146. The center tap 147 of the secondary 146 is connected
through the current meter 25 to the anode 91 of the cell 70, the cathode
92 of the cell 70 being grounded. The opposite ends of the winding
146 are connected to the anodes of a respective one of a pair of diodes
151, each of which has its cathode connected to ground at point 152.
The center tap 147 furnishes a rectified full-wave negative output
to the anode 91 of the cell 70.
To initially condition the central unit 20, the brine tank
52 is filled with approximately 20 pounds of granulated and non-iodized
table salt. Then by connecting inlet port 29 to tap water at a pressure
of about 40 to 65 psi, the tank 52 is filled until float valve 81
shuts off the flow. The flow of the tap water causes switch 80 to
energize pump 77 which pumps prescribed quantities of acid into tank
52. When this is completed, the valves 73 and 64 are opened to ready
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the unit for spray operation.
In operation, an operator orients the wand 30 so that the
nozzle 42 is directed toward the objects ll or 12, the surfaces of
which are to be disinfected. The operator can initiate the sanitizing
procedure by actuating the switch 38 to the sanitize position, thereby
actuating the relay 132 and closing the sets of contacts 132-l and
132-2 to energize the solenoid 72, opening the valves 71, causing
clear water to flow into the inlet 66 of the cell 70. Also, the closing
of the relay contacts 132-2 energizes the pump motor 59, causing the
pump 58 to pump saline solution which mixes with the clear wat0r at
the "T" 63 to enter the inlet 66 of the cell 70. Simultaneously,
the rectifier 140 is energized to supply electrolyzing current to
the cell 70 to electrolyze the solution flowing through the cell 70,
causing a chlorinated disinfecting solution to bè emitted from the
cell outlet 69 through the "T" 68 and the central unit outlet 31,
through the hose 32 and the inlet 35 of the wand 30 and then through
the tube 43 of the wand 30 and out of the nozzle 42 in the form of
a continuous liquid stream upon the objects 11 and 12.
The salinity of the solution, and thus the chlorine strength
of the generated solution, is controlled by coordinating the settings
of the cam on the pump motor shaft 61 to control the displacement
of the pump 58 with the setting of the valve 73 in the clear water
input line. For example, if the ratio of the incoming fresh water
to the brine solution is maintained at about 72:1, a six inch electrolytic
cell will generate 100 parts per million of free chlorine (substantially
entirely in the form of hypochlorous acid) at one-half gallon per
minu~e flow rate. The six inch cell refers to a cell wherein the
electrodes are each 6" X 2 1/4" and operated at 14-17 volts across
the electrodes and at a current of 25-30 amps. The solution may be
further diluted to reduce the parts per million of chlorine where
the particular sanitizing application admits of a lower proportion
of chlorine. Further dilution as, for example, up to 100:1 does not
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adversely affect the pH of the solution, assuming the pH of the incoming
fresh water is 7. Where the pH of the incoming water is more alkaline,
the pump 77 should be varied to increase the proportion of acid into
the solution from two ounces per gallon of saline solution.
The invention admits of the production of a cidal solution
having a substantially greater chlorine concentration by using larger
; cells and connecting them in series. For example, the concentration
can he increased to two thousand parts per million or even greater
should a particular situation require it.
The foregoing description sets forth novel methods and systems
wherein far greater bactericidal effectiveness is achieved in a system
in which disinfecting by means of spraying or fogging solutions upon
solid objects to be disinfected is desired.
As indicated above, the invention has application to the
disinfecting of meat carcasses. The solution of the invention, that
is, the low pH electrolytically generated chlorinated solution, may
be utilized in any one of several different ways. For example, one
operstor employing a single nozzle might spray a carcass for about
thirty seconds at a rate of one-half gallon of solution per minute,
the solution having a chlorine concentration from twenty-five to two
hundred parts per million. Alternatively, the carcass could be subjected
to a multiple nozzle spray as, for example, twelve nozzles spraying
for about ten seconds.
Still another alternative method would involve the prewashing
of the carcass with potable tap water followed immediately by creating
a dense fog of the solution of the invention surrounding the carcass.
In the fogging method, the volume rate of spray is markedly reduced.
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