METHOD FOR DEACTIVATION OF AFLATOXINS

Abstract

The aspects of the present disclosure relate to methods for energy-efficient destruction of organic toxins on the surface of any material, in particular on the surface of organic material. The material contaminated with toxins is exposed to NH.sub.2 and H radicals. Said radicals react chemically with toxins causing their transformation to less poisonous or less carcinogenic substances, or destruction to hydrocarbons and nitrogen-containing benign molecules. Exemplary usage for treatment of seeds, grains, beans, food, feedstock.

Claims

1. A method for the decontamination of a material contaminated with a toxin including a lactone ring, the method comprising: using a gaseous precursor capable of being dissociated into NH.sub.2 and H radicals; introducing the gaseous precursor into a first chamber; dissociating the gaseous precursor into the NH.sub.2 and H radicals in the first chamber; forming a pressure gradient along the first chamber and a second chamber to transfer the NH.sub.2 and H radicals from the first chamber to the second chamber; and exposing the material contaminated with the toxin including the lactone ring to the NH.sub.2 and H radicals in the second chamber.

2. The method of claim 1, wherein the material contaminated with the toxin including the lactone ring includes seeds, grains, beans, nuts, food, feedstock, or other organic or inorganic material including the toxin including the lactone ring.

3. The method of claim 1, wherein the toxin including the lactone ring is on a surface of a material contaminated with aflatoxin.

4. The method of claim 1, further including exposing a surface of a material contaminated with the toxin including the lactone ring to the NH.sub.2 and H radicals in an amount above about 3×10.sup.22 radicals per square meter per micrometer thickness of a toxin layer.

5. The method of claim 1, wherein further includes exposing a surface of the material contaminated with the toxin including the lactone ring to the NH.sub.2 and H radicals in an amount above about 3×10.sup.23 radicals per square meter per micrometer thickness of a toxin layer.

6. The method of claim 1, wherein the toxin including the lactone ring is an aflatoxin including aflatoxins B1, G1, M1, B2, G2 and M2.

7. The method of claim 1, wherein the toxin including the lactone ring is an aflatoxin.

8. A method for the decontamination of a material contaminated with a toxin including a lactone ring, the comprising: using a gaseous precursor capable of being dissociated into NH.sub.2 and H radicals, wherein the gaseous precursor is ammonia (NH.sub.3) or a mixture of nitrogen (N.sub.2) and hydrogen (H.sub.2); introducing the gaseous precursor into a first chamber; dissociating the gaseous precursor into the NH.sub.2 and H radicals in the first chamber; forming a pressure gradient along the first chamber and a second chamber to transfer the NH.sub.2 and H radicals from the first chamber to the second chamber; and exposing the material contaminated with the toxin including a lactone ring to the NH.sub.2 and H radicals in the second chamber.

9. The method of claim 8, wherein the material contaminated with the toxin including the lactone ring includes seeds, grains, beans, nuts, food, feedstock, or other organic or inorganic material including the toxin including the lactone ring.

10. The method of claim 8, wherein the toxin including the lactone ring is on a surface of a material contaminated with aflatoxin.

11. The method of claim 8, further including exposing a surface of a material contaminated with the toxin including the lactone ring to the NH.sub.2 and H radicals in an amount above about 3×10.sup.22 radicals per square meter per micrometer thickness of a toxin layer.

12. The method of claim 8, wherein further includes exposing a surface of the material contaminated with the toxin including the lactone ring to the NH.sub.2 and H radicals in an amount above about 3×10.sup.23 radicals per square meter per micrometer thickness of a toxin layer.

13. The method of claim 8, wherein the toxin including the lactone ring is an aflatoxin including aflatoxins B1, G1, M1, B2, G2 and M2.

14. The method of claim 8, wherein the toxin including the lactone ring is an aflatoxin.

15. A system for the decontamination of material contaminated with a toxin including a lactone ring, comprising: a source of a gaseous precursor capable of being dissociated into NH.sub.2 and H radicals; a dissociation chamber that is in fluid communication with the source of the gaseous precursor and capable of dissociating the gaseous precursor into NH.sub.2 and H radicals; a reaction chamber having a configuration so as to contain the material contaminated with the toxin including a lactone ring and expose the material contaminated with the toxin including a lactone ring to the NH.sub.2 and H radicals, the reaction chamber being in fluid communication with the dissociation chamber; and a vacuum device capable of forming a pressure gradient along both the discharge and the reaction chambers to enable the flow of the NH.sub.2 and H radicals from the dissociation chamber to the reaction chamber so as to expose material contaminated with the toxin including a lactone ring present in the reaction chamber to the NH.sub.2 and H radicals.

16. The system of claim 15, wherein the material contaminated with the toxin including a lactone ring includes seeds, grains, beans, nuts, food, feedstock, or other organic or inorganic material.

17. The system of claim 15, further including a valve disposed between the source of the gaseous precursor and the dissociation chamber and in fluid communication with both and capable of controlling the flow of the gaseous precursor from the source of the gaseous precursor to the dissociation chamber.

18. The system of claim 15, further including a catalyzer that is in fluid communication with the vacuum device and capable of receiving excess NH.sub.2 and H radicals not used in the reaction chamber and other chemical species formed in the reaction chamber and converting them into ecologically benign chemical forms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0021] FIG. 1 shows a schematic of the chemical interaction of the NH.sub.2 and H radicals upon treatment of an aflatoxin (e.g., aflatoxin B1) and the lactone ring thereof.

[0022] FIG. 2 is a schematic of one embodiment of a system of the present disclosure to practice method embodiments of the present disclosure.

[0023] FIG. 3 is a graph that shows a typical pressure along the system presented schematically in FIG. 2.

[0024] FIG. 4 is a graph that shows the reaction time for 90% degradation of the aflatoxins B1 versus the temperature of the grains in the reaction chamber according to Example 1.

[0025] FIG. 5 is a graph that shows the reaction time for 90% degradation of the aflatoxins B1 versus the temperature of the grains in the reaction chamber according to Example 2 at three different plasma powers: 500, 1000, and 1500 W.

DETAILED DESCRIPTION

[0026] Various embodiments are described hereinafter. It should be noted that the specific embodiments are not intended as an exhaustive description or as a limitation to the broader aspects discussed herein. One aspect described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced with any other embodiment(s).

[0027] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the elements (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the claims unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as essential.

[0028] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by embodiments of the present disclosure. As used herein, “about” may be understood by persons of ordinary skill in the art and can vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which it is used, “about” may mean up to plus or minus 10% of the particular term.

[0029] The aspects of the present disclosure relate to methods for chemical modification of toxins including toxins that have a lactone ring to benign molecules using NH.sub.2 and H radicals including toxins (for example, aflatoxins, e.g., aflatoxin B1, G1, M1, B2, G2 and M2, ochratoxins and zearalenone (ZEN)) contaminated kernels, grains, beans, nuts and other agricultural products and materials (e.g., foods and feedstock including corn, wheat, barley and other grain, nuts, etc.) contaminated with toxins. In one embodiment, the source of NH.sub.2 and H radicals the gaseous precursor is the gaseous precursor ammonia (NH.sub.3). In another embodiment, the source of NH.sub.2 and H radicals is the gaseous precursor a mixture of nitrogen (N.sub.2) and hydrogen (H.sub.2). In both embodiments, an electrical discharge is sustained in the dissociation chamber (203) in order to facilitate the formation of NH.sub.2 and H radicals.

[0030] FIG. 1 illustrates an embodiment of the present disclosure including a schematic of the chemical interaction of NH.sub.2 (100) and H (102) radicals and the lactone ring of a toxin (104), for example, an aflatoxin (e.g., aflatoxin B1) upon which the NH.sub.2 (100) and H (102) radicals react. Upon treatment of the lactone ring of the toxin (104) by the NH.sub.2 (100) and H (102) radicals, the lactone ring (104) opens up to form substituent (106). The arrows (108) and (110) in FIG. 1 indicate the direction of the reaction.

[0031] Another embodiment of the present disclosure is a system 200 that includes a gas inlet system (201) that supplies the gaseous precursor through a valve (202) into the dissociation chamber (203) where gaseous radicals are formed. The gas flow with the gaseous radicals formed in the dissociation chamber (203) continues from the dissociation chamber (203) into the reaction chamber (204), which contains the material to be decontaminated (205), typically kernels, grains, beans or nuts and other agricultural products and materials (e.g., foods and feedstock including corn, wheat, barley and other grain, nuts, etc.). The gaseous radicals react with the contaminant of the material to be decontaminated (205) to decontaminate it. Exposure of the surface of the material contaminated with a toxin having a lactone ring, for example, an aflatoxin to NH.sub.2 and H radicals can be in an amount of from about 1×10.sup.22 radicals per square meter per micrometer thickness of the toxin layer to about 1×10.sup.25 radicals per square meter per micrometer thickness of the toxin layer, preferably above about 3×10.sup.22 radicals per square meter per micrometer thickness of the toxin layer or even above about 3×10.sup.23 radicals per square meter per micrometer thickness of the toxin layer. The reaction chamber (204) is pumped with a vacuum pump (206) to enable the flow of introduced gas through the system. The exhaust of the vacuum pump (206) then passes through a catalyzer (207) so that the excess gaseous radicals formed in the dissociation chamber (203) that flow into reaction chamber (204) to be used to decontaminate the material to be decontaminated (205) and are not utilized therein as well as other chemical species formed in the reaction chamber (204) and which may be hazardous are pumped out of the reaction chamber (204) using the vacuum pump (206) and are converted into ecologically benign species, molecules and other chemical forms before being exhausted from system 200 in the direction of arrow (213). The arrows (208), (209), (210), (211), (212) and (213), in FIG. 2 indicate the directional flow of system 200.

[0032] In another embodiment, ammonia is a gaseous precursor used to create suitable concentrations of NH.sub.2 and H radicals and react with the lactone ring of a toxin as shown in FIG. 1. For example, in the embodiment of FIG. 2, ammonia of commercial purity is introduced from the inlet system (201) to the dissociation chamber (203) through a needle valve (202). The gas pressure in the inlet system could be from about 0.5 bars to about 10 bars or from about 1 bar to about 10 bars, but in the preferred embodiment, it is about 1 bar. The entire system in the embodiment of FIG. 2, for this example, is preferably hermetically tight. The vacuum pump (206) enables the flow of introduced gas through the system in FIG. 2, indicated with arrows (208), (209), (210), (211), (212) and (213). The dissociation chamber (203) includes sustaining of an electrical discharge. Preferably, the electrical discharge is an electrode-less discharge, such as a microwave (MW) discharge or a radio-frequency (RF) discharge. The amount of the electrical discharge power can be from about 50 W (W=Watts) to about 2000 W or from about 200 W to about 500 W. The ammonia molecules passing the electrical discharge zone in the dissociation chamber (203) are subject to plasma electrons. The plasma electrons cause ionization and dissociation of ammonia molecules introduced into the discharge chamber (203) through the needle valve (202). The geometry of the dissociation chamber is such that there is an almost constant gradient of gas pressure along the dissociation chamber (203) as shown in FIG. 3 which graphs pressure versus system components. FIG. 3 shows a graph of the typical pressure along the system illustrated in FIG. 2. The inlet pressure can be from about 0.5 bars to about 10 bars or typically about 1 bar up to about 1.5 bar. The knee on the curve (308) occurs at the valve (202). The pressure keeps decreasing along the dissociation chamber (203) until the knee (309), which occurs between the dissociation chamber (203) and the reaction chamber (204). The pressure further decreases along the reaction chamber (204) and reaches the minimal value (310) at the entrance to the vacuum pump (206). There is a pressure jump (311) across the vacuum pump (206), and the pressure assumes the initial value after that (312).

[0033] The condition of an almost constant gradient of gas pressure along the dissociation chamber (203) between the knees (308) and (309) of FIG. 3 can be achieved by using a tube of a rather small diameter, for example about 1 cm, and an appropriate pumping speed of the vacuum pump (206), for example about 100 m.sup.3/h. A typical pressure at the exhaust of the dissociation chamber (203) and the entrance of the reaction chamber (204) is from about 1 mbar (mbar=millibar) to about 100 mbar or from about 5 mbar to about 100 mbar, preferably about 50 mbar as shown in FIG. 3. The initial pressure drop is, therefore, along with the dissociation chamber (203) as shown in FIG. 3.

[0034] Such a distribution of pressure between the knees (308) and (309) of FIG. 3 was found particularly beneficial since it allows for optimal efficiency of the gaseous discharge in terms of producing NH.sub.2 and H radicals. The large pressure gradient along with the dissociation chamber (203) also enables a high speed of gas along with the dissociation chamber (203). In a preferred embodiment, the speed of gas drifting along with the dissociation chamber (203) is from about 50 m/s (m/s=meters per second) to about 343 m/s, from about 50 m/s to about 343 m/s, about 200 m/s to about 300 m/s or about 100 m/s, so the residence time of gaseous molecules and radicals in the dissociation chamber (203) is minimized, typically from about 0.6 ms (ms=millisecond) to about 4 ms, or well below 1 second. The gas drifts from the dissociation chamber (203) to the reaction chamber (204) due to continuous pumping with the vacuum pump (206). The cross-section of the reaction chamber (204) is substantially larger than the cross-section of the dissociation chamber (203) which results in a smaller pressure gradient along with the reaction chamber (204), as revealed from FIG. 3 (the curve between the knees (309) and (310). The residence time of gaseous molecules and radicals is, therefore, longer in the reaction chamber (204) than in the dissociation chamber (203). Such conditions were found beneficial since the moderately large residence time (from about 0.1 s (s=second) to about 10 s or from about 1 s to about 3 s (about 1 second in the preferred embodiment) in the reaction chamber (204) provides enough time for chemical interaction between the NH.sub.2 and H radicals and the organic matter (205) placed inside the reaction chamber (204). Typical organic material (205) placed into the reaction chamber (204) can include kernels, grains, nuts and other agricultural products and materials (e.g., foods and feedstock including corn, wheat, barley and other grain, nuts, etc.) contaminated with toxins. The NH.sub.2 and H radicals interact with toxins present on the organic material (205) according to the scheme shown in FIG. 1. Some radicals cause reactions other than that of FIG. 1. For example, some NH.sub.2 radicals may cause etching of organic material (205) forming different molecules. The most straightforward etching product is hydrogen cyanide (HCN). Hydrogen cyanide is very poisonous for both microorganisms and mammals, so it should not be released to the environment. The vacuum pump (206) enables drifting the gas from the inlet (201) through the dissociation chamber (203) and the reaction chamber (204). In preferred embodiments, the vacuum pump (206) uses mineral oil as a lubricant. The mineral oil is heated to about 60° C. upon the operational temperature of the vacuum pump (206). The hydrogen cyanide interacts chemically with the mineral oil at 60° C., but the interaction may not lead to the complete destruction of HCN. Any poisonous products that are not captured by the pump are converted to benign molecules by passing compressed gas from the vacuum pump (206) to the environment through the catalyzer (207).

[0035] The NH.sub.2 and H radicals are unstable at ambient conditions. Some of the radicals are lost in the gas phase or on any surfaces they touch. The loss on the surface of toxins is beneficial since it leads to the reaction presented in FIG. 1. The loss in the gas phase occurs at three-body collision to assure for the conservation of total energy and momentum:

NH.sub.2+H+particle.fwdarw.NH.sub.3+particle+excessive energy.

[0036] The particle can be any molecule or other radicals, for example, NH.sub.3, H.sub.2, NH.sub.2, NH, H. The excessive energy is close to the dissociation energy of the ammonia molecule to NH.sub.2 and H radicals. The excessive energy is shared between the particle and the ammonia molecule, either as kinetic energy or internal energy providing the internal energy does not equal or exceed the dissociation energy. The loss of radicals in the absence of the particle is highly improbable since the excessive energy cannot appear in the form of the kinetic energy (since the momentum should be conserved), and since it cannot appear in the form of internal energy (since the formed ammonia molecule would dissociate immediately). The frequency of three-body collisions increases as the square of the pressure. At atmospheric pressure, it is prohibitively high resulting in association of the radicals in the gas phase to ammonia molecule in a microsecond. At the pressure of 1 mbar, however, the collision frequency is low enough to assure for the life-time about 1 second. The preferred pressure in the reaction chamber is, therefore, as low as possible. At low pressure, however, the density of gaseous molecules or radicals is low and so is the flux of radicals onto the surface of any material. The pressure of few millibar (for example, from about 1 mbar to about 100 mbar or from about 5 mbar to about 100 mbar, preferably about 50 mbar) at the entrance to the reaction chamber (204) was found a useful compromise between the loss of radicals in the gas phase and the efficacy of chemical reactions as in FIG. 1.

[0037] The NH.sub.2 and H radicals are preferably created by electron impact dissociation of ammonia molecules. The dissociation energy of the bond H—NH.sub.2 is about 435 kJ/mol, which corresponds to a few eV per bond. Such high dissociation energy prevents the application of mostly used dissociation technique, i.e., thermal dissociation on a hot surface. Furthermore, the thermal dissociation may involve the formation of the N.sub.2H.sub.4 molecule, which is regarded as problematic to dissociate and thus form NH.sub.2 radicals. Namely, the N.sub.2H.sub.4 molecules are likely to separate to N.sub.2 and H.sub.2 molecules rather than to NH.sub.2 and H radicals. When electron impact dissociation is employed, it is beneficial to use electrons of moderate energy. Electrons in gaseous discharge assume a range of energies with a distribution close to the normal (i.e., Maxwell-Boltzmann) distribution. The average electron energy in such a distribution is often expressed in terms of the electron temperature. The electron temperature depends on numerous parameters, including the density of discharge power (power normalized to the discharge volume) and the pressure. As a general rule, the electron temperature decreases with increasing pressure at a fixed power density. The pressure distribution as presented in FIG. 2 is beneficial since the electron temperature in the dissociation chamber (203) close to the needle valve (202) is too low to cause significant dissociation of ammonia molecules what would cause unwanted loss of the radicals in the gas phase. Because of the pressure gradient (in one embodiment of FIG. 2) the electron temperature increases in the dissociation chamber from the needle valve (202) towards the reaction chamber (204) reaching the optimal value just before the exhaust from the dissociation chamber (203) to the reaction chamber (204). The electron temperature of between about 2 and about 3 eV at the exhaust from the dissociation chamber (203) to the reaction chamber (204) was found particularly useful.

[0038] The catalyzer (207) serves for the conversion of excessive radicals and other poisonous compounds that might be formed in the reaction chamber (204) upon treatment with organic material (205). The catalyzer (207) typically contains a network or mesh coated with an appropriate catalyst. Optionally, the catalyzer (207) is heated to an elevated temperature (for example, due to the exothermic reactions occurring on the surface of from about 100° C. to about 500° C., usually about 100° C.) to assure for thermal destruction of poisonous gases that might be formed in the reaction chamber (204) upon the interaction of the NH.sub.2 radicals with the organic matter (5).

Example 1

[0039] The configuration presented in FIG. 2 was used for Example 1. The gas inlet (201) in this example was equipped with pressurised ammonia from a metallic flask and a suitable valve that reduces the pressure from that in the bottle (about 8 bar) to 1 bar. The valve (202) was a vacuum-compatible needle valve of adjustable throughput in the range up to about 10 slm (standard litres per minute). The discharge tube of the dissociation chamber (203) had a diameter of about 1 cm and was made from quartz glass. An inductively coupled RF discharge was used as a plasma source. The discharge power was about 500 W. The discharge tube of the dissociation chamber (203) stretches into the reaction chamber (204). The reaction chamber (204) was made from aluminium and is a cubicle of the linear dimension of about 40 cm. The vacuum pump (206) was a combination of a roots blower backed with a two-stage oil-sealed rotary pump. The nominal pumping speed of the roots blower and the rotary pump was about 600 m.sup.3/h and about 80 m.sup.3/h, respectively. The grains material to be decontaminated (205) were evenly distributed in the reaction chamber (203). They had been contaminated artificially with aflatoxins before the treatment. The reaction time for 90% degradation of the aflatoxins B1 versus the temperature of the grains in the reaction chamber (204) is shown in FIG. 4.

Example 2

[0040] The configuration presented in FIG. 2 was also used for Example 2, except that the ammonia in the inlet (201) was replaced with a mixture of hydrogen and nitrogen. The mixture was 25 vol % (volume %) N.sub.2 and 27 vol % H.sub.2. Gases of commercial purity were used. The reaction time for 90% degradation of the aflatoxins B1 versus the temperature of the grains in the reaction chamber (203) is shown in FIG. 5—highest curve (500). The reaction time is too long at the power of 500 W, so higher discharge powers were also used. The highest curve (500) was obtained at the discharge power of 500 W, the middle curve (502) at 1000 W and the lowest curve (504) at 1500 W. The immense discharge power is therefore beneficial for the destruction of aflatoxins, but the results are not as good as when using ammonia as the precursor. Without wishing to be bound by theory, it may be that ammonia is a more suitable source of NH.sub.2 radicals than a gas mixture of N.sub.2 and H.sub.2 since in the latter case the formation of the NH.sub.2 radicals is only feasible by dissociation of the N.sub.2 molecules to N atoms, and subsequent interaction of the N atoms with hydrogen atoms, probably on the surfaces. The triple bond between N atoms in the nitrogen molecule is very strong, hence beneficial dissociation occurs only at high discharge powers.