Note: Descriptions are shown in the official language in which they were submitted.
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MICROBIOCIDAL TREATMENT OF EDIBLE FRUITS AND VEGETABLES
TECHNICAL FIELD
[0001] This invention relates to use of effective antimicrobial solutions for
controlling
contamination of edible fruits and vegetables by various pathogens such as
species of
Listeria, Escherichia, Salmonella, Campylobacter, and others. As used herein,
the term
"edible fruit and vegetable", whether used in the singular or plural, denotes
any harvested
or unharvested edible uncooked fruit or vegetable that is grown for
consumption by
humans.
BACKGROUND
[0002]
Potential contamination of edible fruits and vegetables is a problem that has
existed for many years. Prevention of contamination of edible fruits and
vegetables by
pathogenic microorganisms is important to protect public health. The reduction
of
spoilage caused by microorganisms in vegetable or fruit producing areas (e.g.,
farms,
orchards, etc.), in food processing facilities (e.g., canning or frozen food
facilities), in food
drying facilities, or in wholesale or retail fruit or vegetable distribution
centers and
markets can extend product shelf lives and reduce the amount of food that is
discarded as
waste.
[0003]
Despite prior efforts, there exists a need for improved methods of controlling
microorganisms in facilities producing, processing, distributing or marketing
edible fruits
and vegetables. Bacteria, yeast and molds can accumulate at a variety of
different points
in such operations. The more such points at which viable microorganisms can be
controlled, the lower are the chances of food contamination and the safer the
food
consumed by the purchaser.
[0004] U.S. Pat. No. 6,660,310 describes a method of infusing edible fresh or
freshly cut
fruit or vegetable. The fruit or vegetable is allowed to reach a state of
relative metabolic
stasis or inactivity. An infusion comprising an agent to be infused is
provided and the
fruit or vegetable is submerged therein or coated therewith. Among the agents
referred to
are an aroma enhancing agent, a flavor enhancing agent, a sweetening agent, a
color-
enhancing agent, a nutritionally beneficial agent, a phytochemical, a
pharmaceutical agent,
etc. The infusion is pressurized to a positive or negative pressure for a
period of time.
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The patent indicates that preferably, the surface of the fruit or vegetable is
disinfected with
a bleach solution and/or an antimicrobial soap solution and that more
preferably, the
solution has a concentration in the range of about 0.01% to about 10%, and
most
preferably, the solution has a concentration of about 2%. A listing of
materials used in
experimental approaches indicates that either Clorox Bleach (distributed by
The Clorox
Company of Oakland Calif.) in a 2% solution, or Safesoap@ antimicrobial liquid
hand
soap (distributed by Colgate-Palmolive Company of New York, N.Y.) in a 2%
solution
were used.
[0005] It would be advantageous if a simpler way could be found for treating
fruits and
vegetables against microbiocidal contamination, especially if smaller amounts
of a
microbiocidal agent could be effectively utilized.
BRIEF SUMMARY OF THE INVENTION
[0006] This invention provides a new way of controlling bacterial, yeast,
and/or mold
contamination of edible fruits and vegetables at any of a variety of points in
the
production, processing, distribution or marketing of edible fruits and
vegetables. The
method involves a simple application of a highly effective stabilized
microbiocide
followed by a brief residence time of the microbiocide on the fruit or
vegetable followed
by a suitable washing procedure. In addition, the amount of the biocide used
is less than
that described in the above patent.
[0007] The
aqueous microbiocidal composition is applied to the edible fruit or
vegetable. Accordingly, this embodiment is a method of controlling bacterial,
yeast,
and/or mold contamination of at least one edible fruit or vegetable, which
method
comprises applying to the edible fruit or vegetable an aqueous microbiocidal
composition
containing less than 100 ppm (wt/wt) of active bromine formed from ingredients
comprising water and at least one microbiocidal component selected from:
I) at least one solid-state microbiocidal compound having at least one
bromine atom in the molecule;
II) an aqueous solution or slurry of at least one solid-state microbiocidal
compound having at least one bromine atom in the molecule;
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III) a concentrated aqueous microbiocidal composition having an active
bromine content of at least 50,000 ppm, which composition is formed from
components comprising water and (i) bromine chloride or bromine chloride
and bromine, with or without conjoint use of chlorine and (ii) overbased
alkali metal salt of sulfamic acid and/or sulfamic acid, alkali metal base,
and water, wherein the relative proportions of (i) and (ii) are such that the
atom ratio of nitrogen to active bromine is greater than 0.93, and wherein
the pH of the composition is greater than 7; and
IV) a solid-state microbiocidal composition which is a dewatered
concentrated
aqueous antimicrobial composition of III).
To form the microbiocidal compositions used in this embodiment, the selected
microbiocidal component I), II), III), and/or IV) is mixed with the water.
[0008] In
preferred embodiments, the applied aqueous microbiocidal composition is
allowed to remain in contact with the edible fruit or vegetable for a
microbiocidally-
effective period, which typically is in the range of about 10 seconds to about
30 minutes,
and preferably in the range of about 30 seconds to about 5 minutes, and then
the edible
fruit or vegetable is thoroughly washed at least once with water which,
optionally,
contains at least one surfactant. In this connection and as a general rule,
the higher the
concentration of bromine in the aqueous microbiocidal composition used, the
shorter
should be the time the microbiocidal composition is allowed to be in contact
with the
edible fruit or vegetable. The one or more washes that are utilized should be
thorough
enough to at least remove any and all detectable quantities of the
antimicrobial
composition from the treated edible fruit or vegetable. If a surfactant is
used in one or
more such washes, one or more subsequent water washes are to be employed to
ensure
removal of the surfactant from the edible fruit or vegetable.
[0009] The
above and other embodiments and features of this invention will be still
further apparent from the ensuing description and appended claims.
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FURTHER DETAILED DESCRIPTION OF EMBODIMENTS
OF THE INVENTION
[0010] As can be seen from the above, there are four general groups of bromine-
based
microbiocides used in the practice of this invention. These are more fully
described
below.
Group I) of Bromine-Based Microbiocides
[0011] Among the microbiocidal compositions utilized in the practice of this
invention
are solid-state microbiocidal compounds having at least one bromine atom in
the
molecule. Such compounds are exemplified by (a) 1,3-dihalo-5,5-
dialkylhydantoins in
which both of the halo atoms are bromine atoms and one of the alkyl groups is
a methyl
group and the other is a C14 alkyl group and by (b) 1,3-dihalo-5,5-
dialkylhydantoins in
which one of the halo atoms is a bromine atom and the other is a chlorine
atom, and both
alkyl groups are, independently, C14 alkyl groups. Because of their
effectiveness and
availability as articles of commerce, these solid-state microbiocidal
compounds of (a) and
(b) are more preferred than any other type of solid-state microbiocidal
compound, and
because of superior effectiveness, those of (a) are even more preferred, with
1,3-dibromo-
5,5-dimethylhydantoin being most preferred of all.
[0012] Non-
limiting examples of compounds of type (a) include 1,3-dibromo-5,5-
dimethylhydantoin, 1, 3-dibromo-5 -ethyl-5-methylhydantoin, 1,3-dibromo-5 -n-
propy1-5 -
methylhydantoin, 1, 3-dibromo-5 -isopropyl-5 -methylhydantoin, 1,3 -dibromo-5-
n-buty1-5-
methylhydantoin, 1,3 -dibromo-5-isobuty1-5 -methylhydantoin, 1,3 -dibromo-5 -
sec-butyl-5-
methylhydantoin, 1,3-dibromo-5-tert-buty1-5-methylhydantoin, and mixtures of
any two or
more of them. Of these biocidal agents, 1,3-dibromo-5-isobuty1-5-
methylhydantoin, 1,3-
dibromo-5 -n-propy1-5 -methylhydantoin, and 1,3 -dibromo-5 -ethyl-5-
methylhydantoin are,
respectively, preferred, more preferred, and even more preferred members of
this group
from the cost effectiveness standpoint. Of the mixtures of the foregoing
biocides that can
be used pursuant to this invention, it is preferred to use 1,3-dibromo-5,5-
dimethylhydantoin as one of the components, with a mixture of 1,3-dibromo-5,5-
dimethylhydantoin and 1,3-dibromo-5-ethy1-5-methylhydantoin being particularly
preferred. The most preferred member of this group of microbiocides is 1,3-
dibromo-5,5-
dimethylhydantoin. This compound is available in the marketplace in tablet or
granular
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form under the trade designations XtraBrom 111 biocide and XtraBrom 111T
biocide
(Albemarle Corporation). When a mixture of two or more of the foregoing 1,3-
dibromo-
5,5-dialkylhydantoin biocides is used pursuant to this invention, the
individual biocides of
the mixture can be in any proportions relative to each other.
[0013] Non-limiting examples of compounds of type (b) include N,N'-bromochloro-
5,5-
dimethylhydantoin, N,NI-bromochloro-5-ethy1-5-methylhydantoin, N,NI-
bromochloro-5-
propy1-5-methylhydantoin, N,NI-bromochloro-5-isopropyl-5-methylhydantoin, N,NI-
bromochloro-5-buty1-5-methylhydantoin, N,NI-
bromochloro-5 -is obuty1-5-
methylhydantoin, N,NI-bromochloro-5-sec-buty1-5-methylhydantoin, N,N'-
bromochloro-
5-tert-butyl-5-methylhydantoin, N,N'-bromochloro-5,5-diethylhydantoin, and
mixtures of
any two or more of the foregoing. N,N'-bromochloro-5,5-dimethylhydantoin is
available
commercially under the trade designation Bromicide biocide (Great Lakes
Chemical
Corporation).
Another suitable bromochlorohydantoin mixture is composed
predominantly of N,N'-bromochloro-5,5-dimethylhydantoin together with a minor
proportion by weight of 1,3-dichloro-5-ethy1-5-methylhydantoin. A mixture of
this latter
type is available in the marketplace under the trade designation Dantobrom
biocide
(Lonza Corporation). Of such products, N,N'-bromochloro-5,5-dimethylhydantoin
is a
preferred material because of its commercial availability and its suitability
for use in the
practice of this invention. The designation N,N in reference to, say, N,N'-
bromochloro-
5,5-dimethylhydantoin means that this compound can be (1) 1-bromo-3-chloro-5,5-
dimethylhydantoin, or (2) 1-chloro-3-bromo-5,5-dimethylhydantoin, or (3) a
mixture of 1-
bromo-3 -chloro-5 ,5-dimethylhydantoin and 1-chloro-3-bromo-5,5-
dimethylhydantoin.
Also, it is conceivable that some 1,3-dichloro-5,5-dimethylhydantoin and 1,3-
dibromo-
5,5-dimethylhydantoin could be present in admixture with (1), (2), or (3).
[0014] Methods for preparing compounds of types (a) and (b) above are known
and are
reported in the literature. See for example U.S. Pat. Nos. 3,147,259;
6,508,954; and
6,809,205.
[0015] Other known solid-state microbiocidal compounds which may be utilized
include
N,N'-dihalo-2-imidazolidinones, such as 1 ,3-
dibromo-4,4,5 ,5 -tetramethy1-2-
imidazolidinone, 1 -bromo-3 -chloro-4,4,5 ,5 -tetramethy1-2-imidazolidinone, 1-
chloro-3 -
bromo-4 ,4,5 , 5- tetramethy1-2-imidazolidinone, 1,3 -
dibromo-2 ,2,5 ,5 -
tetramethylimidazolidin-4-one, 1 -bromo-3 -chloro-2 ,2,5 ,5 -
tetramethylimidazolidin-4-one,
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1-chloro-3-bromo-2,2,5,5-tetramethylimidazolidin-4-one. Preparation of such
compounds
is described in U.S. Pat. Nos. 4,681,948; 4,767,542; and 5,057,612.
[0016] Still other known solid-state microbiocidal compounds which may be
utilized are
sulfonyloxy bromoacetanilides such as m-isobutyl-sulfonyloxy bromoacetanilide
and m-
phenyl-sulfonyloxy bromoacetanilide. Still other examples and the preparation
of such
compounds are given in U.S. Pat. No. 4,081,474.
[0017] Another type of known solid-state microbiocidal compounds which may be
utilized are bromine-containing alpha-halo pyruvate oximes such as described
in U.S. Pat.
No. 4,740,524. Examples of such compounds include ethyl 3-bromo-2-(4-
chlorobenzoyloximino)propanoate, ethyl 3-bromo-2-(N' -methylcarbomoyloxi-
mino)propanoate, and ethyl 3-bromo-2-(4-methylbenzoyloximino)propanoate.
[0018] Yet
another type of solid-state bromine-containing microbiocidal compounds
which can be used are non-polymeric quaternary ammonium polybromides described
in
U.S. Pat. No. 4,978,685. Examples of such compounds include N-ethyl-N, N, N-
trimethylammonium tribromide; N-ethyl-N-methylmorpholinium tribromide; N-
benzyl-
N,N-dimethyl-N-myristylammonium dibromochloride; N, N, N, N-tetrabutylammonium
tribromide; and N, N, N, N-tetrabutylammonium dibromochloride.
[0019] Still
other solid-state bromine-containing microbiocidal compounds are known
and reported in the literature.
Group II) of Bromine-Based Microbiocides
[0020] Group
II) constitutes another group of bromine-based microbiocidal
compositions, one or more members of which can be utilized in the practice of
this
invention. These are aqueous solutions or slurries of at least one solid-state
microbiocidal
compound having at least one bromine atom in the molecule. One or more
compounds
referred to above in connection with Group I) can be used in forming these
solutions or
slurries. The solutions can contain any concentration of the respective
compounds up to
their saturation points. If higher concentrations are desired, slurries
containing quantities
in excess of the respective saturation points can be formed and used. Thus,
for some non-
limiting examples of Group II) compounds, see the examples given above in
connection
with Group I). The concentration of the solutions or slurries used are usually
higher than
the desired end use concentration in the washing solution applied to the fruit
or vegetable.
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Group III) of Bromine-Based Microbiocides
[0021] A number of bromine-based microbiocides are typically formed and
provided in
the form of concentrated aqueous solutions, and these concentrated aqueous
solutions
constitute Group III) of the bromine-based microbiocides used pursuant to this
invention.
Such microbiocides are typically stabilized against chemical decomposition and
physical
evaporation of active bromine species by the inclusion in the product during
its formation
of a suitable stabilizing component for the active bromine in the concentrated
solution. A
preferred liquid state bromine-based biocide of this type is an aqueous
biocide
composition comprising water having in solution therein an active bromine
content
derived from (i) bromine chloride or bromine chloride and bromine, with or
without
conjoint use of chlorine, of at least 50,000 ppm (wt/wt) and preferably at
least 100,000
ppm (wt/wt), and (ii) overbased alkali metal salt of sulfamic acid (preferably
a lithium,
sodium, and/or potassium salt of sulfamic acid) and/or sulfamic acid, alkali
metal base
(preferably an oxide or hydroxide of lithium, sodium, and/or potassium) and
water,
wherein the relative proportions of (i) and (ii) are such that the atom ratio
of nitrogen to
active bromine is greater than 0.93, and wherein the pH of the composition is
greater than
7, e.g., in the range of about 12 to 14. Concentrated solutions of this type
are available in
the marketplace, for example, Stabrom 909 biocide (Albemarle Corporation). One
suitable process for producing these concentrated aqueous microbiocidal
solutions is
described in commonly-owned U.S. Pat. No. 6,068,861, issued May 30, 2000, all
disclosure of which is incorporated herein by reference. Another commercial
concentrated aqueous microbiocidal solution that can be utilized in practicing
this
invention is available under the trade designation StabrexTM biocide (Nalco
Chemical
Company). This product also contains active bromine stabilized against
chemical
decomposition and physical evaporation of active bromine species by the
inclusion of
sulfamate. For additional details concerning preparation of aqueous
microbiocidal
solutions stabilized with sulfamic acid, see U.S. Pat. Nos. 6,007,726;
6,156,229; and
6,270,722.
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Group IV) of Bromine-Based Microbiocides
[0022] This
group of bromine-based microbiocides is composed of solid-state
microbiocidal compositions formed by dewatering (i.e., removing at least all
of the liquid
water from) a sulfamate-stabilized aqueous concentrate of active bromine of
Group III)
above. A preferred solid-state microbiocidal composition of this type is
formed by
dewatering an aqueous biocide composition comprising water having in solution
therein
an active bromine content derived from (i) bromine chloride or bromine
chloride and
bromine, with or without conjoint use of chlorine, of at least 50,000 ppm
(wt/wt) and
preferably at least 100,000 ppm (wt/wt), and (ii) overbased alkali metal salt
of sulfamic
acid, wherein the relative proportions of (i) and (ii) are such that the atom
ratio of nitrogen
to active bromine is greater than 0.93, and wherein the pH of the composition
is greater
than 7, e.g., in the range of about 12 to 14. As noted above, concentrated
solutions of this
type are available in the marketplace, for example, Stabrom 909 biocide
(Albemarle
Corporation). Removal of water can be accomplished by flashing or distillation
at reduced
pressure or preferably by spray drying. Such solid state products are
typically in the form
of powders or small particles, but can be compacted into larger forms
preferably with the
aid of one or more suitable binding agents. Further details concerning such
processing are
described in U.S. published Patent Application No. 2004/0022874 Al, all
disclosure of
which relating to formation of such solid-state compositions is incorporated
herein by
reference. In that application are disclosed, inter alia, the following
composition and
process:
[0023] A concentrated liquid biocide composition which comprises an aqueous
solution
of active bromine formed from (a) bromine, bromine chloride or a mixture of
bromine chloride and bromine with (b) alkali metal salt of sulfamic acid
and/or
sulfamic acid, alkali metal base and water, or an aqueous solution of alkali
metal
salt of sulfamic acid formed from (1) alkali metal salt of sulfamic acid
and/or
sulfamic acid, (2) alkali metal base and (3) water, such aqueous solution of
active
bromine having a pH of at least about 7, and wherein the amounts of (a) and
(b) are
such that (i) the content of active bromine in the aqueous solution of active
bromine is above about 160,000 ppm (wt/wt) (ii) the atom ratio of nitrogen to
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active bromine from (a) and (b) is greater than 1 when bromine is used without
bromine chloride, and greater than 0.93 when bromine chloride is used with or
without bromine.
[0024] A
process of forming a solid state bromine-containing biocidal composition,
which process comprises removing the water from an aqueous solution or slurry
of
a product formed in water from (A) (i) bromine, (ii) bromine chloride, (iii) a
mixture of bromine chloride and bromine, (iv) bromine and chlorine in a Br2 to
C12
molar ratio of at least about 1, or (v) bromine chloride, bromine, and
chlorine in
proportions such that the total Br2 to C12 molar ratio is at least about 1;
and (B) (i)
alkali metal salt of sulfamic acid and/or sulfamic acid, and (ii) alkali metal
base,
wherein such aqueous solution or slurry has a pH of at least 7 and an atom
ratio of
nitrogen to active bromine from (A) and (B) of greater than 0.93.
Concentrations of Bromine-Based Microbiocides Used
[0025] To form the aqueous microbiocidal composition applied to the fruit or
vegetable
in order to control bacterial, yeast, and/or mold contamination, thereon or
therein, a
microbiocidally effective amount of at least one particular component is
selected from at
least one of the Groups designated as Groups I), II), III), and IV) and is
dissolved in water.
The microbiocidally effective amount can vary depending upon various factors
such as the
identity of the particular component that is selected from Groups I), II),
III), and IV), the
amount and type of pathogen to be controlled, and the characteristics of the
particular fruit
or vegetable. However, pursuant to this invention, a microbiocidally effective
amount of
an antimicrobial composition of Groups I), II), III), and/or IV) is that
which, upon addition
to water, provides less than 100 ppm of active bromine, preferably in the
range of 0.01 to
75 ppm (wt/wt) of active bromine, and more preferably, in the range of 0.01 to
50 ppm
(wt/wt) in the resultant aqueous solution.
[0026] The aqueous microbiocidal composition applied to the fruit or vegetable
is an
aqueous microbiocidal composition that is formed from a microbiocidal
component of I),
II), III), and/or IV), and water, and that provides less than 100 ppm of
active bromine.
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Preparation Procedures
[0027] When
using at least one solid state microbiocidal compound of Group I), (e.g.,
1,3-dibromo-5,5-dimethylhydantoin or N,N'-bromochloro-5,5-dimethylhydantoin)
or at
least one solid-state microbiocidal composition of Group IV), e.g., a
dewatered
concentrated aqueous biocide composition formed by removing the water from
Stabrom
909 biocide (Albemarle Corporation), the amount of bromine is based on the
weight of
bromine in the solid-state microbiocidal compound or composition. When using a
liquid
component from among the particular components of Group II) or Group III),
e.g., an
aqueous solution or slurry of a solid-state microbiocidal compound having at
least one
bromine atom in the molecule of Group II), such as an aqueous solution of 1,3-
dibromo-
5,5-dimethylhydantoin or of N,N'-bromochloro-5,5-dimethylhydantoin, or a
liquid Group
III) concentrated aqueous microbiocidal composition such as Stabrom 909
biocide
(Albemarle Corporation) or StabrexTM biocide (Nalco Chemical Company), the
amount of
bromine is based on the weight of active bromine in the liquid Group II) or
Group III)
composition. Consequently, the aqueous microbiocidal composition applied to
the fruit or
vegetable contains a microbiocidally-effective amount of at least one aqueous
antimicrobial composition selected from the individual members of Groups I),
II), III),
and/or IV) .
[0028] Preferably, the solid-state components used in forming the aqueous
microbiocidal
compositions that are applied to the fruit or vegetable are made from at least
one particular
component selected from at least one of Groups I), II), III), and IV).
Preferably, the
liquid-state components used in forming the aqueous microbiocidal compositions
that are
applied to the fruit or vegetable are formed from at least one of Groups I),
II), III), and
IV).
[0029] To form the aqueous microbiocidal composition which is applied to the
fruit or
vegetable, components at least one of Groups I), II), III), and IV) are added
to or mixed
with water. One way is to combine the component(s) of Groups I), II), III),
and/or IV)
with enough water to achieve the desired amount of active bromine.
Alternatively, the
component(s) of Groups I), II), III), and/or IV) can be made as preformed
aqueous
concentrated solutions or slurries of the component(s) which are then
typically diluted in
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at least one step with sufficient water to form an aqueous microbiocidal
composition
which is applied to the fruit or vegetable. Other methods can be used when
making up an
aqueous microbiocidal composition. For example, both a preformed aqueous
concentrated
solution or slurry of component(s) of Groups I), II), III), and/or IV) and
more water can be
added to an initial quantity of water or liquid-state mixture of particular
liquid-state
component selected from Groups II) and/or III), or both a preformed aqueous
concentrated
solution or slurry of component(s) of Groups I), II), III), and/ or IV) and a
solid-state
microbiocidal compound or composition from Groups I), II), III), and/or IV)
can be added
to the water.
Analytical Procedures
[0030] In order to measure the quantity of active bromine in water used in
forming an
aqueous microbiocidal composition of this invention, standard well known
analytical
procedures can be used. The term "active bromine" of course refers to all
bromine-
containing species that are capable of biocidal activity. It is generally
accepted in the art
that all of the bromine in the +1 oxidation state is biocidally active and is
thus included in
the term "active bromine". As is well known in the art, bromine, bromine
chloride,
hypobromous acid, hypobromite ion, hydrogen tribromide, tribromide ion, and
organo-N-
brominated compounds have bromine in the +1 oxidation state. Thus these, as
well as
other such species to the extent they are present, constitute the active
bromine content of
the compositions of this invention. See, for example, U.S. 4,382,799 and U.S.
5,679,239.
A well-established method in the art for determining the amount of active
bromine in a
solution is starch-iodine titration, which determines all of the active
bromine in a sample,
regardless of what species may constitute the active bromine. The usefulness
and
accuracy of the classical starch-iodine method for quantitative determination
of bromine
and many other oxidizing agents has long been known, as witness Chapter XIV of
Willard-Furman, Elementary Quantitative Analysis, Third Edition, D. Van
Nostrand
Company, Inc., New York, Copyright 1933, 1935, 1940.
[0031] A
typical starch-iodine titration to determine active bromine is carried out as
follows: A magnetic stirrer and 50 milliliters of glacial acetic acid are
placed in an iodine
flask. The sample (usually about 0.2-0.5g) for which the active bromine is to
be
determined is weighed and added to the flask containing the acetic acid. Water
(50
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milliliters) and aqueous potassium iodide (15% (wt/wt); 25 milliliters) are
then added to
the flask. The flask is stoppered using a water seal. The solution is then
stirred for fifteen
minutes, after which the flask is unstoppered and the stopper and seal area
are rinsed into
the flask with water. An automatic buret (Metrohm Limited) is filled with 0.1
normal
sodium thiosulfate. The solution in the iodine flask is titrated with the 0.1
normal sodium
thiosulfate; when a faint yellow color is observed, one milliliter of a 1 wt%
starch solution
in water is added, changing the color of the solution in the flask from faint
yellow to blue.
Titration with sodium thiosulfate continues until the blue color disappears.
The amount of
active bromine is calculated using the weight of the sample and the volume of
sodium
thiosulfate solution titrated. Thus, the amount of active bromine in a
composition of this
invention, regardless of actual chemical form, can be determined by use of
this method.
[0032] Another standard method for determining active bromine is commonly
known as
the DPD test procedure. This method is well suited for determining very small
amounts of
active bromine in aqueous systems. The standard DPD test for determination of
low
levels of active halogen is based on classical test procedures devised by PalM
in 1974.
See A. T. PalM, "Analytical Control of Water Disinfection With Special
Reference to
Differential DPD Methods For Chlorine, Chlorine Dioxide, Bromine, Iodine and
Ozone",
J. Inst. Water Eng., 1974, 28, 139. While there are various modernized
versions of the
PalM procedures, the recommended version of the test is fully described in
Hach Water
Analysis Handbook, 3rd edition, copyright 1997. The procedure for "total
chlorine" (i.e.,
active chlorine) is identified in that publication as Method 8167 appearing on
page 379,
Briefly, the "total chlorine" test involves introducing to the dilute water
sample containing
active halogen, a powder comprising DPD indicator powder, (i.e., N,N'-
diethyldiphenylenediamine), KI, and a buffer. The active halogen species
present react(s)
with KI to yield iodine species which turn the DPD indicator to red/pink. The
intensity of
the coloration depends upon the concentration of "total chlorine" species
(i.e., active
chlorine") present in the sample. This intensity is measured by a colorimeter
calibrated to
transform the intensity reading into a "total chlorine" value in terms of mg/L
C12. If the
active halogen present is active bromine, the result in terms of mg/L C12 is
multiplied by
2.25 to express the result in terms of mg/L Br2 of active bromine.
[0033] In greater detail, the DPD test procedure is as follows:
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1. To determine the amount of species present in the water which respond to
the
"total chlorine" test, the water sample should be analyzed within a few
minutes of
being taken, and preferably immediately upon being taken.
2. Hach Method 8167 for testing the amount of species present in the water
sample
which respond to the "total chlorine" test involves use of the Hach Model DR
2010
colorimeter. The stored program number for chlorine determinations is recalled
by
keying in "80" on the keyboard, followed by setting the absorbance wavelength
to
530 nm by rotating the dial on the side of the instrument. Two identical
sample
cells are filled to the 10 mL mark with the water under investigation. One of
the
cells is arbitrarily chosen to be the blank. To the second cell, the contents
of a
DPD Total Chlorine Powder Pillow are added. This is shaken for 10-20 seconds
to
mix, as the development of a pink-red color indicates the presence of species
in the
water which respond positively to the DPD "total chlorine" test reagent. On
the
keypad, the SHIFT TIMER keys are depressed to commence a three minute
reaction time. After three minutes the instrument beeps to signal the reaction
is
complete. Using the 10 mL cell riser, the blank sample cell is admitted to the
sample compartment of the Hach Model DR 2010, and the shield is closed to
prevent stray light effects. Then the ZERO key is depressed. After a few
seconds,
the display registers 0.00 mg/L C12. Then, the blank sample cell used to zero
the
instrument is removed from the cell compartment of the Hach Model DR 2010 and
replaced with the test sample to which the DPD "total chlorine" test reagent
was
added. The light shield is then closed as was done for the blank, and the READ
key is depressed. The result, in mg/L C12 is shown on the display within a few
seconds. This is the "total chlorine" level of the water sample under
investigation.
By multiplying this value by 2.25, the level of active bromine in the water
sample
is provided.
Applying Aqueous Solutions to Fruit or Vegetable
[0034]
Various methods can be used for applying to fruit or vegetable an aqueous
solution containing a microbiocidally-effective amount of a stabilized aqueous
antimicrobial composition used pursuant to this invention. For example, the
fruit or
vegetable can be immersed in a tank containing such aqueous solution, or the
fruit or
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vegetable can be subjected to one or more sprays or mists of such aqueous
solution.
Depending upon the size of the facility in which the fruit or vegetable is
being treated, the
spray or mist can be applied by use of hand-held sprays or misting devices.
Alternatively,
the sprays or mists can be applied from nozzles or misting devices disposed
within spray
or misting cabinets or zones into or through which the fruit or vegetable is
conveyed as on
a conveyor belt or other automated conveyor system. A microbiocidally-
effective amount
of stabilized aqueous antimicrobial composition can be applied to the
unharvested fruit or
vegetable before the fruit or vegetable is/are removed from the field or
orchard. For this
purpose, a spray of the composition can be applied to the vegetables while in
the field and
the fruit while on the trees. In the case of fruit trees, the upper portion of
the tree can be
enveloped in a plastic film under which a fine spray, mist, or fog of the
composition can
be applied to the upper portion of the tree including the fruit.
[0035] As
noted above, after application of the aqueous microbiocidal solution to the
fruit or vegetable, the fruit or vegetable is then washed with water in order
to thoroughly
wash away the microbiocidal composition from the fruit or vegetable. The time
period
between the application of the aqueous microbiocidal solution and the
commencement of
the water washing can vary, depending upon such factors as the identity of the
microbiocide used in forming the aqueous microbiocidal solution, the
concentration of the
aqueous microbiocide in the aqueous microbiocidal solution used, and the
nature and
content of microbes, bacteria, fungus, yeast, mold, or other pathogens present
or likely to
be present on the fruit or vegetable. Generally speaking, however, the aqueous
microbiocidal solution should remain in contact with the fruit or vegetable
for a period in
the range of about 10 seconds to about 30 minutes, and preferably in the range
of about 30
seconds to about 5 minutes. Promptly thereafter the thorough water washing
should be
initiated. If desired, a suitable non-toxic surface active agent (surfactant,
detergent, etc.)
can be used in the washing operations to enhance the cleansing activity of the
water wash.
After using a surface active agent in water as a washing medium, the fruit or
vegetable
should be thoroughly washed with pure water.
Edible Fruits or Vegetables
[0036] As pointed out at the outset, "edible fruit or vegetable" denotes any
harvested or
unharvested edible uncooked fruit or vegetable that is grown for consumption
by humans.
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Thus, the methods of this invention are applicable to a wide variety of edible
fruits and
vegetables. Some non-limiting examples of edible fruits include plums,
apricots, peaches,
apples, oranges, lemons, limes, tangerines, grapefruit, bananas, pears,
cherries, grapes,
tomatoes, strawberries, cranberries, blueberries, blackberries, raspberries,
gooseberries,
figs, pineapple, watermelon, pumpkin, cantaloupe, mango, papaya, peanuts,
walnuts,
pecans, almonds, cashew nuts, prunes, raisins, dried figs, dried apricots,
dried pineapple,
dried cranberries, dried apples, and dried bananas, among others. Some non-
limiting
examples of edible vegetables include potatoes, onions, green onions,
shallots, garlic,
carrots, turnips, beets, parsnips, radishes, rutabaga, celery, mushrooms,
corn, okra,
spinach, cabbage, kale, lettuce, broccoli, cauliflower, string beans, peas,
cucumbers,
squash, zucchini, among others. This invention is deemed especially effective
for use in
microbiocidal treatment of leafy vegetables such as, for example, white
cabbage, red
cabbage, kale, iceberg lettuce, romaine lettuce, spinach, mustard greens,
collard greens,
watercress, dandelion, and leafy vegetables used as seasonings such as bay
leaves, mint,
thyme, basil, and oregano.
[0037]
Components referred to by chemical name or formula anywhere in the
specification or claims hereof, whether referred to in the singular or plural,
are identified
as they exist prior to coming into contact with another substance referred to
by chemical
name or chemical type (e.g., another component, a solvent, or etc.). It
matters not what
chemical changes, transformations and/or reactions, if any, take place in the
resulting
mixture or solution as such changes, transformations, and/or reactions are the
natural
result of bringing the specified components together under the conditions
called for
pursuant to this disclosure. Thus the components are identified as ingredients
to be
brought together in connection with performing a desired operation or in
forming a desired
composition. Also, even though the claims hereinafter may refer to substances,
components and/or ingredients in the present tense ("comprises", "is", etc.),
the reference
is to the substance, component or ingredient as it existed at the time just
before it was first
contacted, blended or mixed with one or more other substances, components
and/or
ingredients in accordance with the present disclosure. The fact that a
substance,
component or ingredient may have lost its original identity through a chemical
reaction or
transformation during the course of contacting, blending or mixing operations,
if
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conducted in accordance with this disclosure and with ordinary skill of a
chemist, is thus
of no practical concern.
[0038] Except as may be expressly otherwise indicated, the article "a" or "an"
if and as
used herein is not intended to limit, and should not be construed as limiting,
a claim to a
single element to which the article refers. Rather, the article "a" or "an" if
and as used
herein is intended to cover one or more such elements, unless the text
expressly indicates
otherwise.
[0039] This invention is susceptible to considerable variation in its
practice. Therefore
the foregoing description is not intended to limit, and should not be
construed as limiting,
the invention to the particular exemplifications presented hereinabove.
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