Low-damage grain fungus inactivation method

Abstract

The invention discloses a low-damage grain fungus inactivation method which comprises the following steps: simultaneously contacting ultraviolet light and low-temperature plasma gas with to-be-treated grains to carry out fungus inactivation on the grains, wherein the wavelength of the ultraviolet light ranges from 265 nm to 270 nm, and the concentration of negative ions in the low-temperature plasma gas ranges from 20 * 10 < 6 > ions / cm < 3 > to 30 * 10 < 6 > ions / cm < 3 >. According to the invention, fungi inactivation is simultaneously carried out on grains through ultraviolet light and low-temperature plasma gas, and a good fungi inactivation effect can be obtained by reasonably setting the wavelength of the ultraviolet light, the concentration of the low-temperature plasma gas and the working voltage of the low-temperature plasma generation device; meanwhile, compared with the prior art, a better effect can be achieved on the retention rate of nutrient substances and the integrity of grains; on the premise of ensuring the grain fungus inactivation effect, the damage to grains can be reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of grain fungus inactivation, and particularly relates to a low-damage grain fungus inactivation method. BACKGROUND

[0002] Aflatoxin is a secondary metabolite produced by fungi such as Aspergillus flavus, and has strong carcinogenicity. Crops such as corn and peanuts are easily contaminated by Aspergillus during planting, harvesting and storage. Therefore, preventing Aspergillus contamination and reducing aflatoxin content is an important issue in the field of food safety.

[0003] In the prior art, methods for controlling Aspergillus contamination mainly include:

[0004] Physical method: heat treatment (such as baking) is effective, but it affects the taste and nutritional value of grain. Radiation treatment (such as ultraviolet irradiation) is effective for surface sterilization, but has limited penetration and may cause changes in food ingredients.

[0005] Chemical method: using chemical sterilizing agents, but there are residual and safety problems, which may pollute the environment.

[0006] Biological method: using antagonistic microorganisms to inhibit the growth of Aspergillus, but the effect is affected by environmental factors and has poor stability.

[0007] Cold plasma technology is a new non-thermal treatment technology. Cold plasma can effectively inactivate microorganisms on the surface of food and degrade part of the mycotoxin. However, it has been found through research that HVCP or UVCP treatment can cause damage to the surface of corn kernels and starch particles to a certain extent.

[0008] Patent application "Grain fungus inactivation and toxin degradation device and method" (application number 202310919258.0) discloses a method of using ultraviolet light and low-temperature plasma gas to inactivate fungi on grain, which can achieve good fungus inactivation effect. However, this treatment method does not consider the damage to the nutritional substances of the grain during the treatment process, and the electrostatic adsorption caused by the plasma results in a high broken rice rate.

[0009] In summary, the existing grain fungus inactivation methods in the prior art generally have the problem of causing damage to the grain. SUMMARY

[0010] The purpose of the present application is to provide a low-damage grain fungus inactivation method which can reduce the damage to the grain while ensuring the fungus inactivation effect of the grain.

[0011] The technical solution provided by the present application is as follows:

[0012] A low-damage grain fungus inactivation method comprises:

[0013] The ultraviolet light and the low-temperature plasma gas are simultaneously contacted with the grain to be treated to inactivate the fungus in the grain.

[0014] Preferably, the wavelength of the ultraviolet light is 265nm. 6 ions / cm 3 ions / cm 6 ions / cm 3 .

[0015] Preferably, the UV-LED is used as the ultraviolet light source.

[0016] Preferably, the power of the UV-LED is 50mW / cm 2 .

[0017] Preferably, the low-temperature plasma gas is generated by a low-temperature plasma generating device.

[0018] Preferably, the working voltage of the low-temperature plasma generating device is 10.5kV-11.5kV.

[0019] Preferably, the ultraviolet light and the low-temperature plasma gas are simultaneously contacted with the grain to be treated for 60s-120s.

[0020] Preferably, the wavelength of the ultraviolet light is 265nm.

[0021] Preferably, the negative ion concentration in the low-temperature plasma gas is 25x10 6 ions / cm 3 .

[0022] The present application has the following advantages:

[0023] The low-damage grain fungus inactivation method provided by the present application can reduce the damage to the grain while ensuring the fungus inactivation effect of the grain. DETAILED DESCRIPTION

[0024] The present application will be further described in detail below so that those skilled in the art can implement the present application according to the description.

[0025] The present application provides a low-damage grain fungus inactivation method, and the specific method is as follows.

[0026] The ultraviolet light and the low-temperature plasma gas are simultaneously contacted with the grain to be treated to inactivate the fungus in the grain. 6 ions / cm 3~ 30 x 10 6 ions / cm 3 .

[0027] The application adopts UV-LED as the ultraviolet light source. 2 .

[0028] The low-temperature plasma gas is generated by a low-temperature plasma generating device; wherein the working voltage of the low-temperature plasma generating device is 10.5kV-11.5kV. It is found through research that high working voltage can improve the fungus inactivation rate, but will cause the broken rice rate to increase dramatically.

[0029] As a preferred, the time for the ultraviolet light and the low-temperature plasma gas to contact the grain to be treated simultaneously is 60s-120s.

[0030] In order to further improve the effect of fungus inactivation of the grain, the thickness of the grain layer to be treated is set to be below 2cm, the distance between the ultraviolet light source and the surface of the grain layer is set to be 5cm-10cm, and the grain is turned over more than 3 times during the treatment.

[0031] As a further preferred, the wavelength of the ultraviolet light is 265nm. It is found through research that the 265nm ultraviolet light photon energy (4.68eV) precisely matches the absorption peak (260nm) of Aspergillus flavus DNA, can target and destroy Aspergillus flavus DNA, while the 310nm ultraviolet light photon energy (4.00eV) deviates from the absorption peak, needs 3 times of irradiation time to achieve the same inactivation effect as the 265nm ultraviolet light, and long-time ultraviolet light irradiation will cause thermal damage of the grain. Meanwhile, the 265nm ultraviolet light is strongly absorbed on the surface layer (<0.2mm) of the grain, can avoid damage of deep starch, and the 310nm ultraviolet light has strong penetration (>1mm), causes depolymerization of amylose, and reduces the retention rate of amylose.

[0032] As a further preferred, the negative ion concentration in the low-temperature plasma gas is 25x10 6 ions / cm 3 .

[0033] It is found through research that the use of 20x10 6 ions / cm 3 -30x10 6 ions / cm 3 concentration of negative ions (O2 -OH) can oxidize aflatoxin lactone ring, carry kinetic energy to penetrate spore wall membrane, destroy organelle integrity, and greatly improve the efficiency of fungal inactivation (toxin degradation) compared with low concentration of low temperature plasma gas. When the concentration of low temperature plasma (negative ions) is lower than 20 x 10 6 , the sterilization rate will decrease sharply due to insufficient active particles. When the concentration of low temperature plasma is higher than 30 x 10 6 , electrostatic adsorption will occur, leading to increased grain collision and greatly increased broken rice rate.

[0034] When the concentration of negative ions in the low temperature plasma gas is 25 x 10 6 ions / cm 3 , a good fungal inactivation effect can be achieved, and the broken rice rate is only 0.3%.

[0035] Meanwhile, through experimental verification, the best fungal inactivation synergistic effect can be obtained when the wavelength of ultraviolet light is 265 nm, the concentration of negative ions is 25 x 10 6 ions / cm 3 , and the working voltage of the low temperature plasma generating device is 11 kV.

[0036] The quantitative calculation formula of synergistic effect (synergistic coefficient SI) is:

[0037] SI = actual inactivation rate / (ultraviolet inactivation rate alone + plasma inactivation rate alone);

[0038] When SI > 1.25, it is judged that the synergistic effect is good.

[0039] Embodiment

[0040] Ultraviolet light and low temperature plasma gas are used to contact the grain to be treated simultaneously to inactivate fungi. UV-LED is used as the ultraviolet light source, the power of the UV-LED is 50 mW / cm 2 , and the wavelength of the ultraviolet light is 265 nm. A high-voltage pulse low temperature plasma generating device is used, and the working voltage of the low temperature plasma generating device is 11 kV. The concentration of negative ions in the low temperature plasma gas is 25 x 10 6 ions / cm 3 . The time for the ultraviolet light and the low temperature plasma gas to contact the grain to be treated simultaneously is 90 s. The thickness of the grain layer to be treated is set to 2 cm, and the distance between the ultraviolet light source and the surface of the grain layer is set to 5 cm. During the treatment process, the grain is turned over 3 times.

[0041] Comparative Example 1

[0042] The ultraviolet light and the low-temperature plasma gas are simultaneously contacted with the grain to be treated to inactivate fungi. The UV-LED is used as the ultraviolet light source, the power of the UV-LED is 50 mW / cm 2 , and the wavelength of the ultraviolet light is 310 nm. The high-voltage pulse low-temperature plasma generating device is used, the working voltage of the low-temperature plasma generating device is 11 kV, and the negative ion concentration in the low-temperature plasma gas is 25 x 10 6 ions / cm 3 . The time for the ultraviolet light and the low-temperature plasma gas to be simultaneously contacted with the grain to be treated is 90 s. The thickness of the grain layer to be treated is set to 2 cm, the distance between the ultraviolet light source and the surface of the grain layer is set to 5 cm, and the grain is stirred 3 times during the treatment.

[0043] Comparative Example 2

[0044] The ultraviolet light and the low-temperature plasma gas are simultaneously contacted with the grain to be treated to inactivate fungi. The UV-LED is used as the ultraviolet light source, the power of the UV-LED is 50 mW / cm 2 , and the wavelength of the ultraviolet light is 265 nm. The high-voltage pulse low-temperature plasma generating device is used, the working voltage of the low-temperature plasma generating device is 11 kV, and the negative ion concentration in the low-temperature plasma gas is 15 x 10 6 ions / cm 3 . The time for the ultraviolet light and the low-temperature plasma gas to be simultaneously contacted with the grain to be treated is 90 s. The thickness of the grain layer to be treated is set to 2 cm, the distance between the ultraviolet light source and the surface of the grain layer is set to 5 cm, and the grain is stirred 3 times during the treatment.

[0045] Comparative Example 3

[0046] The ultraviolet light and the low-temperature plasma gas are simultaneously contacted with the grain to be treated to inactivate fungi. The UV-LED is used as the ultraviolet light source, the power of the UV-LED is 50 mW / cm 2 , and the wavelength of the ultraviolet light is 265 nm. The high-voltage pulse low-temperature plasma generating device is used, the working voltage of the low-temperature plasma generating device is 9.5 kV, and the negative ion concentration in the low-temperature plasma gas is 25 x 10 6 ions / cm 3 . The thickness of the grain layer to be treated is set to 2 cm, the distance between the ultraviolet light source and the surface of the grain layer is set to 5 cm, and the grain is stirred 3 times during the treatment.

[0047] Comparative Example 4

[0048] The ultraviolet light and the low-temperature plasma gas are simultaneously contacted with the grain to be treated to inactivate fungi. The UV-LED is used as the ultraviolet light source, the power of the UV-LED is 50 mW / cm2 The wavelength of the ultraviolet light is 265 nm. A high-voltage pulse low-temperature plasma generating device is used, the working voltage of the low-temperature plasma generating device is 12.5 kV, and the negative ion concentration in the low-temperature plasma gas is 25 x 10 6 ions / cm 3 The thickness of the grain layer to be treated is set to 2 cm, the distance between the ultraviolet light source and the surface of the grain layer is set to 5 cm, and the grain is stirred 3 times during the treatment.

[0049] Comparative Example 5

[0050] The grain is treated by hot air drying to inactivate fungi, the hot air temperature is 60℃, and the treatment time is 90s.

[0051] The fungal inactivation (toxin degradation) effects of the treated grain in the examples and comparative examples 1-5 are compared, and the results are shown in Table 1.

[0052] Table 1 Comparison of fungal inactivation effects of examples and comparative examples

[0053]

[0054]

[0055] In Table 1, * indicates a significant difference (p < 0.01) from the optimal group; the toxin detection method is HPLC-MS / MS (national standard GB5009.22-2016), and the initial spore amount of Aspergillus flavus is 3.7 x 10 7 / g.

[0056] The nutrients and quality of the treated grain in the examples and comparative examples 1-5 are compared, and the results are shown in Table 2.

[0057] Table 2 Comparison of nutrients and quality of treated grain in examples and comparative examples

[0058]

[0059] In Table 2, * indicates a significant difference (p < 0.01) from the optimal group.

[0060] From the comparison of the fungal inactivation effects of the examples and the comparative examples, it can be seen that in the examples of the present application, a low-temperature non-thermal mechanism (plasma temperature < 40℃) is used to achieve a fungal inactivation rate of 98.7%, while the active nutrient components of the grain are retained. In Comparative Example 1, the wavelength of the ultraviolet light used is 310 nm, which results in a significant reduction in the nutrient components of the grain. For example, the amylose retention rate in Comparative Example 1 (89.3%) is reduced by about 9% compared to the amylose retention rate in the example (98.2%). In Comparative Example 2, the negative ion concentration in the low-temperature plasma gas is 15 x 10 6 ions / cm3 The low-temperature plasma gas concentration is low, resulting in a significant decrease in the fungus inactivation effect (toxin degradation rate). For example, the degradation rate of aflatoxin B1 (degradation rate 95.4%) is reduced by more than 40% relative to the example (degradation rate 52.1%). The working voltage of the low-temperature plasma generating device in Comparative Example 3 is 9.5 kV, and the fungus inactivation rate is reduced relative to the example. In Comparative Example 4, the working voltage of the low-temperature plasma generating device is 12.5 kV, and a good fungus inactivation rate can be obtained, but static adsorption is generated due to the excessively high voltage, resulting in a high broken rice rate (11.8%). Although the traditional heat treatment fungus inactivation method in Comparative Example 5 has a high fungus inactivation rate and toxin degradation rate, it causes greater damage to nutrients in the grain, and the nutrient damage is irreversible. For example, the vitamin B1 retention rate in the example can reach 95.0%, while the vitamin B1 retention rate in Comparative Example 5 can only reach 68.2%.

[0061] At the same time, the example 1 can obtain the best fungus inactivation synergistic effect by reasonably setting the ultraviolet light wavelength, low-temperature plasma gas concentration, and working voltage of the low-temperature plasma generating device relative to Comparative Examples 1-4.

[0062] The present application can simultaneously inactivate fungi in grain by ultraviolet light and low-temperature plasma gas, and can obtain a better fungus inactivation effect by reasonably setting the ultraviolet light wavelength, low-temperature plasma gas concentration, and working voltage of the low-temperature plasma generating device. At the same time, the example has a better effect on the retention rate of nutrients and the preservation of grain integrity (low broken rice rate) relative to each comparative example.

[0063] Although the embodiments of the present application have been disclosed as above, it is not limited to the use listed in the specification and embodiments, and can be fully applied to various fields suitable for the present application, and additional modifications can be easily realized by those skilled in the art, and therefore the present application is not limited to specific details and the examples shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A method for low-damage inactivation of fungi in grains, characterized in that, include: The grain is inactivated by simultaneously exposing it to ultraviolet light and low-temperature plasma gas. The ultraviolet light has a wavelength of 265nm to 270nm, and the negative ion concentration in the low-temperature plasma gas is 20×10⁻⁶. 6 ions / cm 3 ~30×10 6 ions / cm 3 .

2. The method for low-damage inactivation of grain fungi according to claim 1, characterized in that, UV-LED is used as the ultraviolet light source.

3. The method for low-damage inactivation of grain fungi according to claim 2, characterized in that, The power of the UV-LED is 50mW / cm². 2 .

4. The method for low-damage inactivation of grain fungi according to any one of claims 1-3, characterized in that, Low-temperature plasma gas is generated using a low-temperature plasma generator. The operating voltage of the low-temperature plasma generator is 10.5kV to 11.5kV.

5. The method for low-damage inactivation of grain fungi according to claim 4, characterized in that, The contact time between ultraviolet light and low-temperature plasma gas and the grain to be treated is 60s to 120s.

6. The method for low-damage inactivation of grain fungi according to claim 5, characterized in that, The wavelength of the ultraviolet light is 265 nm.

7. The method for low-damage inactivation of grain fungi according to claim 6, characterized in that, The concentration of negative ions in the low-temperature plasma gas is 25 × 10⁻⁶. 6 ions / cm 3 .

Images