Field of the invention

The present invention relates to a chlorine dioxide releasing composition. More particularly, present invention relates to a stable chlorine dioxide releasing composition and process for preparation of stable chlorine dioxide releasing composition.

Background of the Invention
Chlorine dioxide is known to be an excellent disinfectant as well as a strong oxidizing agent. Its bactericidal, viricidal, algicidal, fungicidal, bleaching, and deodorizing properties are well documented in the prior art. Regulatory approvals now led to growing acceptance of its use in reducing pathogens in food processing applications such as poultry chill water tanks, beef and pork carcasses washes, and raw agricultural commodities. Chlorine dioxide has many advantages over traditional chlorine-based biocides due to its greater selectivity towards bacterial cell membranes. Chlorine dioxide inactivates microorganisms by oxidizing key components in proteins that regulate cell metabolism. Cell death is caused by a loss of permeability control and ultimately membrane potential. By oxidizing these specific protein components, chlorine dioxide is reduced to inactive by-products.
Also known to the prior art is the difficulty of storing and transporting chlorine dioxide, that results in various apparatuses and compositions to accomplish the on-site production of chlorine dioxide.
Commercially, chlorine dioxide is produced from a variety of aqueous solutions of chlorine-containing salts. These aqueous solutions are disadvantageous because of the difficulty in packaging and application as well as the danger of uncontrolled rate of release of chlorine dioxide which often results in unacceptably high concentrations of the chlorine dioxide gas. Chlorine dioxide cannot be compressed and stored, as can chlorine, and aqueous solutions of chlorine dioxide rapidly degrade through evaporation and sun light. Aqueous chlorine dioxide chemistry is highly complex and often unwanted side reactions occur which lower yield and generate higher valent oxy-chloro species such chloride, chlorite, and chlorate.
Chlorine dioxide gas is prohibited from transportation. It is explosive in air at concentrations of about 10% and has a low threshold limit value (TLV) classification by OSHA of 0.1 ppm to workers. As a result of these limitations, it must be produced at the-point-of use.
Powdered or dry compositions that release chlorine dioxide upon addition of water might be considered able to solve the foregoing problems associated with stabilized chlorine dioxide or metal chlorite solutions. Such dry compositions are disclosed in U.S. Pat. Nos. 2071091; 2071094; 2022262; and 2482891. However, these dry compositions do not provide any means to control release rate of chlorine dioxide and are accordingly prone to uncontrolled overproduction of chlorine dioxide.
US5885543 discloses controlled release of chlorine dioxide through dry composition. However, the stability issues such as chlorine dioxide outgassing before the point-of-use, risk of corrosion due to presence of co-additives such as calcium chloride and undesirable storage and shipping losses remain unsolved
The commonly known chlorine dioxide precursors are a source of chlorite ions, may be in the form of chlorite compounds or any metal chlorite, as well as mixtures thereof. The generation of chlorine dioxide from metal chlorite or some other chlorine dioxide liberating compound can be broadly classified into three categories including the acidification of chlorites, the oxidation of chlorites, or the reduction of chlorites. Chlorine dioxide generation is thus usually activated by the addition of an acid, the addition of an oxidant like bleach (i.e. hypochlorite or hypochlorous acid), persulfate, or chlorine, or the addition of a reductant to chlorates (chemical or electrochemical).
Stability is the major issue while using metal chlorite as a source of chlorite ions. The anhydrous form of some metal chlorite such as sodium chlorite is particularly hazardous. Any sudden heating can result in "hot points' which can cause explosive decomposition into chloride, chlorate and further degradation products of chlorate. Sodium chlorite with at least 5% by weight of water do not possess such risk of decomposition. When a sodium chlorite product containing about 5% or more water is exposed to sudden heating, the heat is absorbed by the water in sufficient amount to prevent chemical disproportionation. However, sodium chlorite containing at least 5% water congeals into a solid mass if it is submitted to a temperature above about 38° C and subsequently cooled. Also, sodium chlorite poses stability challenges when formulated with other excipients.
Although various efforts had been taken in the past to develop a composition for producing chlorine dioxide at the point-of-use in a controlled or sustained release form, there is still a long felt need to develop an alternative, simple and an efficient product and a process for developing the stable controlled release compositions of these active ingredients. Also, there is a need for developing such composition, wherein the composition overcomes drawbacks of the prior art and exhibits increased stability with respect to active ingredients responsible for chlorine dioxide release. The stability of chlorine dioxide release composition upon storage/use is a key problem in the art and the same is to be addressed.

Object of the invention
It is an objective of the invention to provide a stable composition capable of releasing chlorine dioxide at the point-of-use.
It is an objective of the invention to provide a stable composition capable of extending controlled rate of release of chlorine dioxide at the point-of-use.
Another objective of the invention is to provide a process of preparing stable composition capable of releasing chlorine dioxide at the point-of-use.
Yet another objective of the present invention is to provide a method of controlling postharvest pathogens using stable composition of chlorine dioxide according to the invention.
Summary of the invention
In an aspect of the present invention, a composition capable of releasing chlorine dioxide, comprising a first part and at least one second part:
(a) said first part comprising a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base as a stabilizer; and
(b) said second part comprising at least one acid generating species;
wherein chlorine dioxide is released when the stabilized source of chlorite ions of first part is brought in contact with acid generating species of the second part.
In another aspect of the present invention, a composition capable of releasing chlorine dioxide, said composition comprising a first part and at least one second part:
(a) said first part comprising a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base as a stabilizer; and
(b) said second part comprising at least one acid generating species adsorbed onto an inert carrier;
wherein chlorine dioxide is released when the stabilized source of chlorite ions of first part is brought in contact with acid generating species of the second part.
In another aspect of the present invention, a process of preparing a composition capable of releasing chlorine dioxide comprising a first part and at least one second part, wherein said first part comprising a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base; and wherein said second part comprising at least one acid generating species adsorbed onto an inert carrier, said process comprising:
(a) mixing a source of chlorite ions with an inorganic base to obtain a mixture;
(b) retaining the mixture onto an infusing medium to form the first part of the composition; and
(c) adsorbing at least one acid generating species onto an inert carrier to form the second part.
In another aspect of the present invention, a process for generating chlorine dioxide at a point-of-use, said process comprising:
(a) providing a composition comprising a first part and at least one second part, wherein the first part comprises a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base, and wherein the second part comprises at least one acid generating species adsorbed onto an inert carrier;
(b) contacting the chlorite ions of the first part with the acid generating species of the second part to release chlorine dioxide at the desired point-of-use.
In another aspect of the present invention, a method of controlling post-harvest pathogens, said method comprising:
(a) providing a composition comprising a first part and at least one second part, wherein the first part comprises a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base, and wherein the second part comprises at least one acid generating species adsorbed onto an inert carrier;
(b) contacting the chlorite ions of the first part with the acid generating species of the second part to release chlorine dioxide at the desired point-of-use; and
(c) conveying the generated chlorine dioxide to the locus of the stored harvest.
In another aspect of the present invention, a kit comprising:
(a) at least one component comprising a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base; and
(b) at least a second component comprising at least one acid generating species adsorbed onto an inert carrier.
In another aspect of the present invention, a kit comprising:
(a) at least one component comprising a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base;
(b) at least a second component comprising at least one acid generating species adsorbed onto an inert carrier; and
(c) means for conveying the generated chlorine dioxide to the locus of the stored harvest.
In another aspect of the present invention, a composition capable of releasing chlorine dioxide is used against postharvest pathogens.

Detailed description of the invention
In accordance with the present invention, there is provided a composition capable of releasing chlorine dioxide such that the composition remains stable during storage and transport; and releases chlorine dioxide only at the point-of-use.
It has been found by the present inventors, surprisingly, that a composition capable of releasing chlorine dioxide in a controllable manner and at the point-of-use can be obtained by stabilizing the source of chlorite ions retained on an infusing medium with a stabilizer. The stabilizer prevents chlorine dioxide outgassing before the time of their intended use by prohibiting migration of protons in the aluminosilicates comprising the infusing medium. The presence of stabilizer also prevents source of chlorite ions from deterioration in the presence of inherent moisture of the infusing medium. The stabilized source of chlorite ions prepared using the stabilizer does not suffer deterioration problem during storage and transport. Therefore, full amount of source of chlorite ions concentration remains available for release of chlorine dioxide at the desired point-of-use.
The nature and substance of the present invention, as well as its objects and advantages, will be more clearly perceived and fully understood by referring to the following description. Thus, there can be several aspects to the present invention such as the composition, the process for preparing such a composition, a process for generating chlorine dioxide at the desired point-of-use, a method for controlling post-harvest pathogens, and a kit for such generation of chlorine dioxide and for use in such post-harvest control. These aspects of the invention, and the several embodiments thereof, are described herein.
Each of the embodiments described herein apply to any one or all of the aspects described above.
With respect to the present invention, source of chlorite ions being stabilized using an inorganic base as a stabilizer is also referred to as “stabilized source of chlorite ions”.
In an embodiment of the present invention, the source of chlorite ions may be selected from the group comprising a chlorite salt of an alkali metal, an alkaline earth metal, a transition metal, or a mixture thereof.

In an embodiment, the source of chlorite may preferably be selected from the group comprising sodium chlorite, potassium chlorite, barium chlorite, calcium chlorite, and magnesium chlorite, and any combination thereof. However, these sources of chlorite ions are exemplary and non-limiting.

In an embodiment, the chlorite ions source is sodium chlorite.
In an embodiment, the sodium chlorite is a dry technical grade sodium chlorite comprising about 80% by weight sodium chlorite and 20% by weight sodium chloride.

In an embodiment, the composition comprises from about 0.1% to about 30% of source of chlorite ions of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the composition comprises from about 0.5% to about 20% of source of chlorite ions of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the source of chlorite ions comprises from about 1% to about 10% of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the first part of the chlorine dioxide releasing composition comprises a stabilizer.

In an embodiment, the first part of the chlorine dioxide releasing composition comprises a stabilizer and an infusing medium.

In an embodiment, the first part of the chlorine dioxide releasing composition comprises a stabilizer, an infusing medium and a bulking agent.

In an embodiment, the stabilizer is an inorganic base selected from the group comprising potassium carbonate, potassium bicarbonate, potassium hydroxide, potassium sulfate, potassium phosphate (dibasic or tribasic), potassium borate, potassium tetraborate, potassium acetate, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium sulfate, sodium phosphate (dibasic or tribasic), sodium borate, sodium acetate, ammonium carbonate, ammonium bicarbonate, ammonium hydroxide, ammonium sulfate, ammonium phosphate (dibasic or tribasic), ammonium borate, ammonium acetate, calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium sulfate, calcium phosphate (dibasic or tribasic), calcium borate, calcium acetate, magnesium carbonate, magnesium bicarbonate, magnesium hydroxide, magnesium sulfate, magnesium phosphate (dibasic or tribasic), magnesium borate, magnesium acetate, sodium percarbonate, ammonium hydrogen bicarbonate and lithium bicarbonate, and combinations thereof.

In an embodiment, the stabilizer is an inorganic base selected from dibasic or tribasic sodium phosphate.
In an embodiment, the stabilizer is tribasic sodium phosphate.
In an embodiment, the first part comprises from about 0.1% to about 80% of the stabilizer of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the first part comprises from about 1% to about 70% of the stabilizer of the total weight of first part of the chlorine dioxide releasing composition.
In an embodiment, the first part comprises from about 5% to about 60% of the stabilizer of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the source of chlorite ions and the stabilizer are combined in a ratio from about 1:5 to about 1:40 in the first part of chlorine dioxide releasing composition.

In an embodiment, the first part of the chlorine dioxide releasing composition comprises an infusing medium.

In an embodiment, the infusing medium in the first part of chlorine dioxide releasing composition is selected from the group comprising of zeolite, synthetic zeolite (modernite), natural zeolite (chabazite, clinoptilolite), clays (bentonite, kaolin, attapulgite and halloysite), anhydrous clays, calcined clays (metakaolin, spinel phase kaolin, calcined bentonite, calcined halloysite and calcined attapulgite), and acidified synthetic zeolites.

In an embodiment, the infusing medium is zeolite.
In an embodiment, the infusing medium comprises from about 1% to about 90% of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the infusing medium comprises from about 5% to about 80% of the total weight of first part of the chlorine dioxide releasing composition.
In an embodiment, the infusing medium comprises from about 10% to about 70% of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the infusing medium has an optimum moisture content.

In an embodiment, the infusing medium has a moisture content 15% or less by weight.
In an embodiment, the source of chlorite ions is retained or provided onto the porous structure of the infusing medium. In this embodiment, the retention is such that infusing medium provides a surface for adsorption and absorption to the stabilized source of chlorite ions. Other terms used to describe this interaction between infusing medium and stabilized source of chlorite ions include binding or trapping, each of which is contemplated to be within the definition of absorption and/or adsorption. Such an interaction provides partial exposure for the stabilized source of chlorite ions to contact acid generating species and thus facilitate controlled release of chlorine dioxide when stabilized source of chlorite ions of the first part is brought in contact with acid generating species of the second part.

In an embodiment, the first part of the chlorine dioxide releasing composition comprises a bulking agent.

In an embodiment, the bulking agents in the first part of the chlorine dioxide releasing composition are selected from the group comprising of sodium chloride, sodium sulphate, propylene oxide, sodium alginate, sodium silicate, sodium sulfite, 1-2-benzisothiazolin-3-one, 1-3-butylene glycol dimethyacrylate, diallylphthalate, diethylene glycol, diethanolamine, diethylene glycol, epichlorohydrin, glyceryl triacetate, hexamethylene tetramine, isopropyl alcohol, maleic acid, sodium fluoride, sodium nitrite, triethanolamine, triethyl phosphate, and acetic anhydride.

In an embodiment, the bulking agent in the first part of chlorine dioxide releasing composition is selected from sodium chloride and/or sodium sulphate.

In an embodiment, the bulking agent comprises from about 0.1% to about 70% of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the bulking agent comprises from about 0.5% to about 60% of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the bulking agent comprises from about 1% to about 50% of the total weight of first part of the chlorine dioxide releasing composition.

In an embodiment, the chlorine dioxide releasing composition comprises, in the second part, at least one acid generating species.

In an embodiment, the acid generating species is selected from the group comprising citric acid, acetic acid, tartaric acid, acetic anhydride, lactic acid, ascorbic acid, glycolic acid, salicylic acid, benzoic acid, sulfamic acid, sodium acid sulfate, aluminium sulfate, ferrous sulfate, ferric chloride, and any combination thereof.

In an embodiment, the acid generating species are ferric chloride and/or ferrous sulphate.

In an embodiment, the acid generating species comprises from about 0.1% to about 50% of the total weight of second part of the chlorine dioxide releasing composition.

In an embodiment, the acid generating species comprises from about 1% to about 30% of the total weight of second part of the chlorine dioxide releasing composition.

In an embodiment, the acid generating species is adsorbed onto an inert carrier.

In an embodiment, the inert carrier may be selected from the group comprising of clay, finely powdered pumice, fired diatomaceous earth, kaolin, talc, acid clay, calcium carbonate, and other minerals, anhydrous clays selected from bentonite, kaolin, attapulgite and halloysite, and calcined clays selected from metakaolin, spinel phase kaolin, calcined halloysite and calcined attapulgite.

In an embodiment, the inert carrier is bentonite.
In an embodiment, the acid generating species is brought in contact with the inert carrier by way of adsorption, absorption or sorption.

In an embodiment, the inert carrier comprises from about 0.1% to about 80% of the total weight of second part of the chlorine dioxide releasing composition.

In an embodiment, the inert carrier comprises from about 0.5% to about 70% of the total weight of second part of the chlorine dioxide releasing composition.

In an embodiment, the inert carrier comprises from about 1% to about 60% of the total weight of second part of the chlorine dioxide releasing composition.
In an embodiment, the source of chlorite ions of the first part and acid generating species of the second part are combined in a ratio from 1:1 to 1:5 to release chlorine dioxide.

According to an embodiment, the present inventors have found that the rate of chlorine dioxide release could be desirably controlled by varying amount of source of chlorite ions.

In an embodiment, the present inventors have found that the rate of chlorine dioxide release could be desirably controlled by varying the amount of the infusing medium.

In an embodiment, the present inventors have found that the rate of chlorine dioxide release could be desirably controlled by varying the amount of acid generating species.

In an embodiment, the present inventors have found that the rate of chlorine dioxide release could be desirably controlled by varying the amount of the inert carrier of second part.

In an embodiment, the preferred amounts of the source of chlorite ions, the infusing medium, the acid generating species and the inert carrier may be selected as described hereinabove.

In an embodiment of the present invention, a process of preparing a composition capable of releasing chlorine dioxide comprising a first part and at least one second part, wherein said first part comprising a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base; and wherein said second part comprising at least one acid generating species adsorbed onto an inert carrier, said process comprising:
(a) mixing a source of chlorite ions with an inorganic base to obtain a mixture;
(b) retaining the mixture onto an infusing medium to form the first part of the composition; and
(c) adsorbing at least one acid generating species onto an inert carrier to form the second part.
In an embodiment, the source of chlorite ions is prepared by:
(a) mixing a source of chlorite ions and a stabilizer to obtain a blend; and
(b) mixing the blend to obtain stabilized source of chlorite ions.
In an embodiment, the source of chlorite ions is prepared by:
(a) mixing a source of chlorite ions, a stabilizer and an infusing medium to obtain a blend; and
(b) mixing the blend to obtain stabilized source of chlorite ions.
In an embodiment, the source of chlorite ions is prepared by:
(a) mixing a source of chlorite ions, a stabilizer, an infusing medium and a bulking agent to obtain a blend; and
(b) mixing the blend to obtain stabilized source of chlorite ions.
In an embodiment, the process for the preparation of the composition capable of releasing chlorine dioxide comprises a step of preparing a stabilized acid generating species.
In an embodiment, the step of preparing the acid generating species comprises adsorbing at least one acid generating species onto an inert carrier.
In an embodiment, the step of preparing the acid generating species comprises adsorbing at least one acid generating species onto an inert carrier by the mixing acid generating species with the inert carrier.
In an embodiment, the step of preparing a stabilized source of chlorite ions comprises preparation of stabilized sodium chlorite by
(a) adding sodium chlorite, stabilizer, infusing medium and bulking agent to obtain a blend; and
(b) mixing the blend to obtain stabilized sodium chlorite.
In an embodiment, the step of preparing the acid generating species comprises adsorbing ferric chloride onto an inert carrier by mixing ferric chloride and bentonite to obtain ferric chloride adsorbed onto bentonite.

In an embodiment, the step of preparing the acid generating species comprises adsorbing ferric chloride onto bentonite to obtain ferric chloride granules.

In an embodiment, the chlorine dioxide releasing composition comprises at least one of additives, sequestrates, dyes, extenders and the like in order to increase the stability and efficiency of the composition.

In an embodiment, the chlorine dioxide releasing composition comprises a first part and at least one second part, said first part comprising from about 0.1% to about 30% w/w of source of chlorite ions, from about 0.1% to about 70% stabilizer, from about 1.0% to about 90% w/w of infusing medium, and from about 0.1% to about 30% w/w of bulking agent, and the second part comprising from about 0.1% to about 50% w/w of an acid generating species adsorbed onto from about 0.1% to about 30% w/w of inert carrier.

In an embodiment, the chlorine dioxide releasing composition comprises a first part and at least one second part, said first part comprising from about 0.1% to about 30% w/w of sodium chlorite, from about 0.1% to about 70% tribasic sodium phosphate, from about 1.0% to about 90% w/w of zeolite and from about 0.1% to about 30% w/w of sodium sulfate, and the second part comprising from about 0.1% to about 50% w/w of ferric chloride adsorbed onto from about 0.1% to about 30% of bentonite.

In an embodiment, composition capable of releasing chlorine dioxide may be used for disinfection and decontamination of ware house, whole buildings or whole rooms, bio-safety cabinets in research or academic laboratories, hospital rooms, medical and dental facilities, textiles comprising clothing, shelters, and tents, bathrooms and shower facilities, kitchen and dining facilities, laundries, food handling equipment and contact surfaces in processing environments (including fresh produce), boat cabins or rooms in recreational vehicles, and in smaller spaces such as isolators, filtered housings, water purifiers, and laundries, and surfaces of personal use items such as boots and shoes, tools, cosmetic applicators, mouthwash, toothpastes, surgical and dental instruments, and drawing instruments, and contaminated objects in the interior chamber of a closable, vented container for sterilizing microbiologically contaminated surgical instruments, medical equipment, textiles, uniforms, fresh produce, or other contaminated surfaces.
In an embodiment, the composition capable of releasing chlorine dioxide may be used for post-harvest control of pathogens from the surface of harvested fruits and vegetables.
According to an embodiment, the present invention provides use of the composition capable of releasing chlorine dioxide, the composition comprising first part and at least one second part, said composition comprising in the first part a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base as a stabilizer; and in the second part at least one acid generating species; wherein chlorine dioxide is released when the source of chlorite ions is allowed to react with acid generating species for reduction of postharvest pathogens.
In an embodiment, the composition capable of releasing chlorine dioxide may be used against many postharvest pathogens which are pathogenic and spoilage microorganisms, such as E. coli O157:H7, Salmonella sp., Penicillium expansum, and Xanthomonas campestris pv. campestris. It reduces microorganism populations by oxidation, mainly through the one-electron transfer mechanism.
According to another embodiment, the composition capable of releasing chlorine dioxide according to the present invention may be used to reduce postharvest pathogens in fruits, tubers and vegetables with longer shelf life. Such postharvest fruits, tubers and vegetables include but not limited to potato, sweet potato, cassava, yam, dahlia, tomato, onion, and carrot etc.
According to an embodiment, the chlorine dioxide releasing composition of the present invention may be used in potatoes to control Black Leg (Erwinia carotovora), Dry rot (Fusarium coeruleum), Brown rot (Ralstonia solanacearum), Soft rot (Erwinia Pectobacterium), Potato wart (Synchytrium endobioticum), Late blight (Phytophthora infestans), Scab (Streptomyces Scabies), Sclerotium rot (Sclerotium rolfsii), Silver scurf (Spondyocladium atrovirens), Charcoal rot (Macrophomina Phaseolina).
According to another embodiment of the present invention, a method of controlling post-harvest pathogens is provided, said method comprising exposing the stored harvest to chlorine dioxide generated using the composition according to the present invention.
According to another embodiment of the present invention, a method of controlling post-harvest pathogens is provided, said method comprising exposing the stored harvest such as fruits, tubers and vegetables to an agrochemically effective amount of chlorine dioxide release using the composition according to the present invention.
According to another embodiment of the present invention, a method of controlling post-harvest pathogens is provided, said method comprising exposing the stored harvest such as fruits, tubers and vegetables, to an agrochemically effective amount of chlorine dioxide wherein chlorine dioxide is released when the stabilized source of chlorite ions is brought in contact with acid generating species.
According to another embodiment of the present invention, the method of controlling post-harvest pathogens such as E. coli O157:H7, salmonella sp., penicillium expansum, xanthomonas campestris pv. campestris etc is provided.
According to another embodiment of the present invention, a method of controlling pathogens is provided, said method comprising exposing the empty warehouses, storage chambers and other desired locations to chlorine dioxide released using the composition according to the present invention.
According to an embodiment of the present invention, a kit is provided, said kit comprising in separate packings, the stabilized source of chlorite ions in a first pack and an acid generating species in the second pack so that chlorine dioxide is released when the components of both the packs of the kit are brought in contact with each other.
According to an embodiment of the present invention, a kit is provided, said kit comprising in separate packings, the stabilized source of chlorite ions in a first pack and an acid generating species in the second pack, wherein chloride dioxide is controllably generated at the point of use when the components of the first and second pack are brought into contact.
Within the scope of the invention, rate of chlorine dioxide release (upon bringing source of chlorite ions and acid generating species in contact) can be controlled in any of several ways, including by appropriately selecting the amount of infusing medium in first part and the amount of inert carrier in the second part.

In an embodiment, the rate of release of chlorine dioxide may be controlled by the controlled inclusion of external water/ moisture or any source providing proton when stabilized source of chlorite ions and acid generating species are brought in contact.

According to another embodiment, suitable means may be adopted to bring stabilized source of chlorite ions and acid generating species in contact with each other that allow efficient mixing of stabilized source of chlorite ions and acid generating species adsorbed onto inert carrier to facilitate chlorine dioxide release.

According to another embodiment; the stabilized source of chlorite ions and acid generating species adsorbed onto inert carrier are brought in contact with each other by placing them in a vibratory or rotary shaker that allows homogeneous mixing of stabilized metal chlorite and acid generating species adsorbed onto inert carrier.

In an embodiment, the vibratory or rotary shaker allow continuous contact of stabilized source of chlorite ions and acid generating species adsorbed onto inert carrier such that once chlorine dioxide is released upon contact of stabilized source of chlorite ions and acid generating species adsorbed onto inert carrier, the exhausted/ consumed actives may be replaced by loaded actives in a continuous manner. This has been found to facilitate uninterrupted release of chlorine dioxide.

According to an embodiment of the present invention, the first part and the second part of the chlorine dioxide releasing composition may be prepared in dry/solid form.
According to an embodiment of the present invention, the first part and the second part of the chlorine dioxide releasing composition may be prepared in the dry/ solid form as powder, granules, pellets, tablets etc.

The following examples illustrate the invention, but by no means intend to limit the scope of the claims.

Example 1:
Preparation of chlorine dioxide releasing composition:
a) Preparation of stabilized 3.2% sodium chlorite;
4.3g sodium chlorite, 30.0g Tribasic Sodium phosphate, 44.4g zeolite, and 10 g bulking agents were mixed together to obtain a blend. The blend was then mixed to obtain stabilized sodium chlorite as first part.
b) Preparation of 13.6% ferric chloride granules;
14 g ferric chloride was mixed with 86 g bentonite to obtain ferric chloride adsorbed onto bentonite.

The Example-1 is further illustrated as:

Ingredients Quantity (%)
3.2% Sodium chlorite
Sodium chlorite 4.3
Zeolite 44.7
Tribasic Sodium Phosphate 30.0
Bulking agent (Sodium Chloride) 5.0
Bulking agent (Sodium Sulphate) 5.0
Water q.s.
Total 100
13.6% Ferric Chloride
Ferric chloride 14
Bentonite granules 86

Example 2:

Ingredients Quantity (%)
0.5 % Sodium Chlorite
Sodium chlorite 0.75
Zeolite 48.25
Tribasic Sodium Phosphate 30.0
Bulking agent 10.0
Water q.s.
Total 100
8 % Ferric Chloride
Ferric chloride 8.5
Bentonite granules 91.5

The chlorine dioxide releasing composition with Sodium chlorite, Tribasic Sodium Phosphate, Zeolite, Bulking agent as first part; and in the second part, ferric chloride and bentonite are mixed in a given ratio shown above and prepared as per the process of Example 1.

Example 3:

Ingredients Quantity (%)
3.2 % Sodium chlorite
Sodium chlorite 4.1
Zeolite 49.9
Tribasic Sodium Phosphate 25
Bulking agent 10.0
Water q.s.
Total 100
13.6 % Ferric Chloride
Ferric chloride 14
Bentonite granules 16

The chlorine dioxide releasing composition with Sodium chlorite, Tribasic Sodium Phosphate, Zeolite, Bulking agent as first part; and in the second part, ferric chloride and bentonite are mixed in a given ratio shown above and prepared as per the process of Example 1.

Example 4:

Ingredients Quantity (%)
15 % Sodium chlorite
Sodium chlorite 19.4
Zeolite 24.6
Tribasic Sodium Phosphate 40
Bulking agent 5.0
Water q.s.
Total 100
16 % Ferric Chloride
Ferric chloride 16.5
Bentonite granules 83.5

The chlorine dioxide releasing composition with Sodium chlorite, Tribasic Sodium Phosphate, Zeolite, Bulking agent as first part; and in the second part, ferric chloride and bentonite are mixed in a given ratio shown above and prepared as per the process of Example 1.

Example 5:

Ingredients Quantity (%)
3.2 % Sodium chlorite
Sodium chlorite 4.3
Zeolite 47.7
Tribasic Sodium Phosphate 40.0
Water q.s.
Total 100
13.6 % Ferric Chloride
Ferric chloride 14
Bentonite granules 86

The chlorine dioxide releasing composition with Sodium chlorite, Tribasic Sodium Phosphate, Zeolite, Bulking agent as first part; and in the second part, ferric chloride and bentonite are mixed in a given ratio shown above and prepared as per the process of Example 1.

Example 6:

Ingredients Quantity (%)
3.2 % Sodium chlorite
Sodium chlorite 4.3
Zeolite 44.7
Tribasic Sodium Phosphate 30.0
Corn Starch 10.0
Water q.s.
Total 100
13.6 % Ferric Chloride
Ferric chloride 14
Bentonite granules 86

The chlorine dioxide releasing composition with Sodium chlorite, Tribasic Sodium Phosphate, Zeolite, corn starch as first part; and in the second part, ferric chloride and bentonite are mixed in a given ratio shown above and prepared as per the process of Example 1.

Stability of Chlorine Dioxide releasing composition
The compositions prepared according to the process disclosed in the present invention was tested to determine the percentage of degradation of sodium chlorite and ferric chloride in the compositions under 14 days AHS study (Table-1).
Table-1
Example 14 AHS (% Degradation)
Sodium Chlorite Ferric Chloride
Example 1 3.6 % 4.5 %
Example 2 5% 4.5%
Example 3 4.4% 4.5%
Example 4 4.7% 3.2%
Example 5 2.8% 3.6%

The compositions prepared according to the process described in the invention found to remain stable under 14 days AHS study with around 1-5% degradation of sodium chlorite and 1-5% degradation of ferric chloride.

Comparative study to understand role of stabilizer
Example 7 was prepared without stabilizer agent to analyze the impact of stabilizer on the stability of metal chlorite composition of the first part. The sample was prepared using all the ingredients similar to Example-1 except Tribasic Sodium Phosphate (TSP), a stabilizer and formulated as per the process disclosed in Example-1. It was found that sample prepared without stabilizer did not sustain even for two days when kept in ambient conditions. Moreover, a strong smell of chlorine gas was detected. Therefore, sample did not keep further for 14 days AHS study because of its strongly oxidizing nature. On the contrary, the sample prepared according to Example-1 remained quite stable throughout the ambient as well as 14 days AHS study. This suggested that stabilizer is responsible for imparting stability to the metal chlorite composition that prevents undesirable reaction of metal chlorite with zeolite (Table-2).

Table-2
Ingredients Batch No 08 (with TSP) Exm-1 Batch No 41 (without TSP) Exm-7
Quantity (%) Quantity (%)
3.2% Sodium chlorite 3.2% Sodium chlorite
Sodium chlorite 4.3 4.4
Zeolite 44.7 69.6
Tribasic Sodium Phosphate Dodecahydrate 30.0 0
Bulking agent 10.0 11.0
Water q.s. q.s.
Total 100 100
Observation Remained stable at ambient as well as in 14 AHS study. Two days shelf stored sample showed intense smell of gas and deteriorated. Formulation failed.

Determination of Chlorine Dioxide release from the composition:
2.5g of stabilized sodium chlorite composition of first part and 2.5 g ferric chlorite adsorbed onto bentonite as a second part of Example-1 was taken in a round bottomed flask which was connected to two buffered potassium iodide traps placed in series. The round bottomed flask was placed over magnetic stirrer. The mixture was stirred at 100-120 rpm. Freshly prepared 100ml buffered potassium iodide solution was added into the traps. The assembly was arranged in such a way that air entered in the round bottomed flask, facilitated chlorine dioxide gas generation and passed through the vent connected to the traps. The generated chlorine dioxide was trapped in buffered potassium iodide solution. The air was allowed to pass through the round bottomed flask for 30 minutes. The yellow colored buffered potassium iodide solution was collected at every 30-minute interval. The trapped Chlorine Dioxide was quantified by titration method. The yellow color buffered potassium iodide was titrated against 0.05N sodium thiosulfate solution. First end point was recorded as soon as the solution became colorless. A volume of 10 mL of 10% sulfuric acid solution was added to the flask and titration continued until solution became colorless again as second end-point. Similarly, chlorine dioxide release was determined for compositions of Exm-3 as disclosed in the invention (Table-3).
(Table-3)
Hours 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 Total % Release
#
Example 1 34.3 13.99 4.43 1.52 0.29 - - - - 54.53
Example 3 33.01 12.43 8.05 1.00 0.58 - - - - 55.07
It was found that, chlorine dioxide generation triggered instantly and around 30% chlorine dioxide was released within 0.5 hours of mixing of first part and the second part. In every composition, more than 50% of chlorine dioxide is released within 2.5 hours of application which is considered to be reasonably good for desired controlled release characteristic of the composition.
Postharvest Treatment of Potato by Chlorine Dioxide
The composition (of Exm-1) prepared according to the present invention is tested for postharvest prevention of potatoes stored in warehouse from pathogen damage. During postharvest storage, potatoes are susceptible for pathogen damage especially caused by Dry rot (Fusarium coeruleum), Brown rot (Ralstonia solanacearum), Soft rot (Erwinia pectobacterium), Late blight (Phytophthora infestans) and Silver scurf (Spondyocladium atrovirens).
Accordingly, 500g of 3.2% stabilized sodium chlorite and 500g of 13.6% ferric chloride granules was mixed together to treat 500MT of potatoes. The arrangement of potato in the warehouse having capacity to store 1500MT potatoes was such that the potatoes were first packed in net bags and these net bags were then vertically stacked in the warehouse. The warehouse was maintained at 4-8°C temperature recommended for potato postharvest storage (Table-5).
Potato Treatment with Chlorine Dioxide store in cold storage
Table-5
Trial Date Observation Date Chamber capacity (MT) Quantity (Kg)
Soft Rot Dry Rot Silver Scurf
01-Jul-17 23-Jul-17 1517 10 No No No

The chlorine dioxide was allowed to be released in the warehouse for around 6 hours. After 20 days, potatoes stored in the warehouse were inspected to observe undesirable bacterial and fungal infections in the form of soft rot, dry rot and silver scurf.
Soft rot disease of potato crops is commonly recognized by soft, wet, cream-to tan-colored flesh, normally surrounded by a dark brown to black ring. With the progression of bacterial soft rot in potatoes, an undeniably foul odor stems out from the infected potato. We found that potatoes that received chlorine dioxide treatment remain free from soft rot infection. No such bacterial growth observed on treated potatoes.
Dry rot is the most important fungal rot of potatoes caused by Fusarium species. Fusarium dry rot is characterized by an internal light to dark brown or black rot of the potato tuber-and it is usually dry. The rot may develop at an injury such as a bruise or cut. No such bacterial growth observed on treated potatoes.
Silver scurf (Helminthosporium solani) is a ubiquitous fungal blemish disease of potatoes. Infection can originate from seed tubers, the soil or from spores remaining in store. Symptoms are normally present at harvest, but the disease develops in store. Affected skin is weakened, prone to scuffing and can wrinkle due to moisture loss. No occurrence of silver scurf growing on the stored potatoes were seen.

Therefore, it was concluded that chlorine dioxide treatment found to be very effective in controlling bacterial and fungal infections such as soft rot, dry rot and silver scurf.

Treatment of Infected Potatoes
With an objective to check the effectiveness of Chlorine dioxide composition on the already infected potatoes, few trials were conducted in chambers loaded with potatoes infected with dry rot, sliver scurf and soft rot. Tubers were treated for around 6 hours in the chamber. The treated potatoes were observed after 30 days. It was observed that the bacterial and fungal growth didn’t spread further, and no further infestation was seen on the stored potatoes. This was manifested by visually observing the treated potatoes. After receiving chlorine dioxide treatment, the infected potatoes remained in same state with no further increase in infection and the infected zone remained in same condition as it was before the treatment. Details of treatment are presented in Table 6.
Table 6
Warehouse Type of chamber Chamber No. Chamber capacity (MT) Area (Cu.Ft.) Amount of chlorine dioxide composition (Kg) % infestation of Soft Rot and others in potatoes
Before Treatment
After Treatment
I Bag Store 1 3,013 3,61,620 81 5% 5%
II Bag Store 2 3,000 3,60,192 81 5% 5%
III Bag Store 2 3,203 3,84,384 86 6% 6%
IV Bag Store 4 4,498 5,39,784 121 4% 4%

The present invention overcomes the problem of uncontrolled production of chlorine dioxide by way of preparing a chlorine dioxide releasing composition using stabilised source of chlorite ions and acid generating species. This composition would not generate chlorine dioxide unless stabilized source of chlorite ions brought in contact with acid generating species. The present invention thus provides a composition for the release of chlorine dioxide at the point-of-use when stabilised source of chlorite ions and acid generating species are allowed to come in contact with each other to generate chlorine dioxide. The chlorine dioxide generating composition prepared using present invention does not suffer deterioration problem during storage and transport. Therefore, full amount of active metal chlorite concentration remains available to generate chlorine dioxide.
Further, the chlorine dioxide generating composition of the invention is capable of producing chlorine dioxide while in a completely dry state without the need for water or water vapor. In addition, it was surprisingly found that by varying ratios of components of the metal chlorite composition and acid generating species adsorbed onto the inert carrier, a wide range of chlorine dioxide release rates may be achieved. Also, the chlorine dioxide generating composition is capable (upon agitation) of renewed generation of chlorine dioxide. The chlorine dioxide-releasing compositions of the invention may be used in the disinfection of post-harvest produces during their storage, preservation and shipment. Further, the chlorine dioxide generating composition of the present invention is capable of releasing chlorine dioxide without addition of water or water vapor.
,CLAIMS:1. A composition capable of releasing chlorine dioxide comprising:
(a) first part comprising a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base as a stabilizer; and
(b) second part comprising at least one acid generating species;
wherein chlorine dioxide is released when the stabilized source of chlorite ions of said first part is brought in contact with acid generating species of said second part.
2. The composition as claimed in claim 1, wherein said acid generating species is adsorbed onto an inert carrier;
3. The composition as claimed in claim 1, wherein said source of chlorite ions is selected from the group comprising a chlorite salt of an alkali metal, an alkaline earth metal, a transition metal, or combination thereof.
4. The composition as claimed in claim 1, wherein said source of chlorite ions is selected from sodium chlorite, potassium chlorite, barium chlorite, calcium chlorite, magnesium chlorite and combination thereof.
5. The composition as claimed in claim 1, comprises from about 0.1% to about 30% source of chlorite ions of the total weight of the composition.
6. The composition as claimed in claim 1, wherein infusing medium is selected from zeolite, synthetic zeolite, modernite, natural zeolite, chabazite, clinoptilolite, clay, bentonite, kaolin, attapulgite, halloysite, anhydrous clays, calcined clays, metakaolin, spinel phase kaolin, calcined bentonite, calcined halloysite, calcined attapulgite and acidified synthetic zeolites.
7. The composition as claimed in claim 1, comprises from about 1% to about 90% infusing medium of the total weight of the composition.
8. The composition as claimed in claim 1, wherein stabilizer is an inorganic base selected from the group comprising potassium carbonate, potassium bicarbonate, potassium hydroxide, potassium sulfate, potassium phosphate, potassium borate, potassium tetraborate, potassium acetate, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium sulfate, sodium phosphate (dibasic or tribasic), sodium borate, sodium acetate, ammonium carbonate, ammonium bicarbonate, ammonium hydroxide, ammonium sulfate, ammonium phosphate (dibasic or tribasic), ammonium borate, ammonium acetate, calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium sulfate, calcium phosphate, calcium borate, calcium acetate, magnesium carbonate, magnesium bicarbonate, magnesium hydroxide, magnesium sulfate, magnesium phosphate, magnesium borate, magnesium acetate, sodium percarbonate, ammonium hydrogen bicarbonate and lithium bicarbonate, and combinations thereof.
9. The composition as claimed in claim 1, comprises from about 0.1% to about 80% stabilizer of the total weight of the composition.
10. The composition as claimed in claim 1, wherein the source of chlorite ions and the stabilizer are combined in a ratio from about 1:5 to about 1:40 in the first part of chlorine dioxide releasing composition.
11. The composition as claimed in claim 1, wherein the acid generating species is selected from the group comprising of citric acid, acetic acid, tartaric acid, acetic anhydride, lactic acid, ascorbic acid, glycolic acid, salicylic acid, benzoic acid, sulfamic acid, sodium acid sulfate, aluminium sulfate, ferrous sulfate, ferric chloride, and any combination thereof, preferably ferric chloride and/or ferrous sulphate.
12. The composition as claimed in claim 1, comprises from about 1% to about 30% acid generating species of the total weight of the composition.
13. The composition as claimed in claim 2, wherein inert carrier is selected from the group comprising of clay, finely powdered pumice, fired diatomaceous earth, kaolin, talc, acid clay, calcium carbonate, and other minerals, anhydrous clays selected from bentonite, kaolin, attapulgite and halloysite, and calcined clays selected from metakaolin, spinel phase kaolin, calcined halloysite and calcined attapulgite, preferably bentonite.
14. The composition as claimed in claim 2, comprises from about 0.5% to about 70% inert carrier of the total weight of the composition.
15. The composition as claimed in claim 1, wherein the source of chlorite ions of the first part and acid generating species of the second part are combined in a ratio from 1:1 to 1:5 to release chlorine dioxide.
16. A process of preparing a composition for releasing chlorine dioxide comprising
(a) mixing a source of chlorite ions with an inorganic base to obtain a mixture;
(b) retaining the mixture onto an infusing medium to form the first part of the composition; and
(c) adsorbing at least one acid generating species onto an inert carrier to form the second part.
17. A process for generating chlorine dioxide at a point-of-use comprising:
(a) providing a composition comprising first part containing a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base, and wherein the second part comprises at least one acid generating species adsorbed onto an inert carrier;
(b) contacting the chlorite ions of the first part with the acid generating species of the second part to release chlorine dioxide at the desired point-of-use.
18. A method of controlling post-harvest pathogens comprising:
(a) providing a composition comprising a first part containing a source of chlorite ions retained in an infusing medium and a second part comprises at least one acid generating species adsorbed onto an inert carrier;
(b) contacting the chlorite ions of the first part with the acid generating species of the second part to release chlorine dioxide at the desired point-of-use to generate chlorine dioxide and
(c) conveying the generated chlorine dioxide to the locus of the stored harvest.
19. A kit comprising a composition for generating chlorine dioxide containing
(a) at least one component comprising a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base; and
(b) at least a second component comprising at least one acid generating species adsorbed onto an inert carrier.
(c) means for conveying the generated chlorine dioxide to the locus of the stored harvest.
20. A composition for use in the reduction of postharvest pathogens in fruits, tubers and vegetables comprising at least one component comprising a source of chlorite ions retained in an infusing medium wherein the source of chlorite ions is stabilized using an inorganic base and at least a second component comprising at least one acid generating species adsorbed onto an inert carrier.
21. The composition as claimed in claim 1 and 19 is used for controlling bacterial and fungal infections.