Method for Killing Aspergillus flavus Spores by Infrared Radiation in Coordination with Essential Oil Fumigation

Abstract

The disclosure discloses a method for killing A. Flavus spores by infrared radiation in coordination with essential oil fumigation, and belongs to the technical field of sterilization. The method is to treat A. Flavus spores by medium and short wave infrared radiation in combination with essential oil fumigation. The disclosure provides a method for killing A. Flavus spores by medium and short wave infrared radiation in coordination with essential oil fumigation. On the one hand, air residual heat and energy of medium and short wave infrared radiation are fully used to make a material heated up rapidly, and on the other hand, essential oil on the surface of the material penetrates the cell membrane of A. Flavus spores, and further damages protein on the membrane and internal organelles in combination with the heat effect. The process is easy in operation, low in energy consumption, pollution-free and high in sterilization efficiency, and can be used for purifying bulk grains.

Claims

1. A method for killing A. Flavus spores, comprising: performing essential oil fumigation and performing medium and short wave infrared radiation in sequence, wherein the medium and short wave infrared refers to infrared with a wavelength of 0.7-4 μm; the medium and short wave infrared radiation is performed at a temperature of 90-120° C. for 5-15 min; the essential oil used for essential oil fumigation is selected from one or more of aromatic oils of labiate plants; and the essential oil fumigation is performed at a dose of 405-1620 mg for 2-8 hours.

2. The method of claim 1, wherein the content of the main component carvacrol in the essential oil used for essential oil fumigation is equal to or greater than 88.3% by mass.

3. A method for preventing aflatoxin contamination in agricultural products, using medium and short wave infrared radiation in combination with essential oil fumigation to treat the agricultural products, and comprising: fumigating the agricultural products with essential oil first, and then radiating the agricultural products with medium and short wave infrared to prevent aflatoxin contamination in the agricultural products.

4. The method of claim 3, wherein the medium and short wave infrared refers to infrared with a wavelength of 0.7-4 μm; and the medium and short wave infrared radiation is performed at a temperature of 90-120° C. for 5-15 minutes.

5. The method of claim 3, wherein the essential oil fumigation is performed at a dose of 405-1620 mg for 2-8 hours.

6. The method of claim 3, wherein the medium and short wave infrared refers to infrared with a wavelength of 0.7-4 μm; the medium and short wave infrared radiation is performed at a temperature of 90-120° C. for 5-15 minutes; the essential oil used for essential oil fumigation is selected from one or more of aromatic oils of labiate plants; and the essential oil fumigation is performed at a dose of 405-1620 mg for 2-8 hours.

7. The method of claim 6, wherein the content of the main component carvacrol in the essential oil used for essential oil fumigation is equal to or greater than 88.3% by mass.

8. The method of claim 3, wherein the agricultural products comprise rice, corn, peanuts, oats or nuts.

9. A method for removing A. Flavus spores from agricultural products, comprising: fumigating the agricultural products with essential oil first, and then radiating the agricultural products with medium and short wave infrared to remove A. Flavus spores from the agricultural products.

10. The method of claim 9, wherein the medium and short wave infrared refers to infrared with a wavelength of 0.7-4 μm; and the medium and short wave infrared radiation is performed at a temperature of 90-120° C. for 5-15 minutes.

11. The method of claim 9, wherein the essential oil fumigation is performed at a dose of 405-1620 mg for 2-8 hours.

12. The method of claim 9, wherein the medium and short wave infrared refers to infrared with a wavelength of 0.7-4 μm; the medium and short wave infrared radiation is performed at a temperature of 90-120° C. for 5-15 minutes; the essential oil used for essential oil fumigation is selected from one or more of aromatic oils of labiate plants; and the essential oil fumigation is performed at a dose of 405-1620 mg for 2-8 hours.

13. The method of claim 12, wherein the content of the main component carvacrol in the essential oil used for essential oil fumigation is equal to or greater than 88.3% by mass.

14. The method of claim 9, wherein the agricultural products comprise rice, corn, peanuts, oats or nuts.

Description

DETAILED DESCRIPTION

[0033] The preferred examples of the disclosure will be described below. It should be understood that the examples are for better illustrating the disclosure and are not intended to limit the disclosure.

[0034] 1. A. flavus is from the China General Microbiological Culture Collection Center, has a preservation number of A. flavus CGMCC 3.4408, and is disclosed in Jiang Jing, Zhang Yuming, Quan Juncheng, et al. Effects of Far-infrared Radiation on A. flavus Spores from Rice and Toxin-producing Ability [J]. Food and Machinery, 2018, v.34; No.198(04):81-85+226.

[0035] 2. Determination method of the number of spores: Refer to GB 4789.15-2016 National Food Safety Standard-Food Microbiological Inspection-Mold and Yeast Counting. An A. flavus spore suspension of a suitable dilution gradient is prepared and a Rose Bengal medium is inoculated with the A. flavus spore suspension. The A. flavus spores are cultured and the number of A. flavus colonies is counted.

[0036] 3. The essential oil used in the following examples and comparative examples is a Lamiaceae plants aromatic oil, namely oregano essential oil, including carvacrol (equal to or greater than 88.3% by mass) and thymol (equal to or greater than 2.5% by mass), and purchased from Jiangxi Xuesong Natural Medicinal Oil Co., Ltd.

EXAMPLE 1

[0037] The dish cover of a medium inoculated with an A. flavus spore suspension of an appropriate concentration was removed, and the medium was placed in a 3 L polypropylene plastic fresh-keeping box. 810 mg of essential oil was accurately weighed and dropped onto filter paper in the box, and the medium in the box was fumigated for 4 h in a constant temperature incubator at 45° C. An infrared drying oven was set to 100° C. and started heating. After the measured temperature on a display was stable, the dish cover was removed, and the fumigated medium was placed on a tray, radiated for 5 min, and then taken out and cooled to room temperature. After the 5.sup.th day of culture, the number of colonies on the medium remained unchanged. Compared with Comparative Example 1, the number of A. flavus spores decreased by 4.08±0.11 log CFU/ml, and this is was much higher than the decrease in the number of A. flavus spores on the surface of the solid medium in Comparative Example 2 and Comparative Example 3, indicating that the combined treatment of intermediate-wave infrared radiation and essential oil fumigation had a better sterilization effect than single treatment.

[0038] Compared with Comparative Example 4, the order of combined treatment had a significant impact on the sterilization effect, and the treatment method of performing fumigation first and then infrared radiation was conducive to the coordination of essential oil and heat to achieve a better sterilization effect.

[0039] Compared with Comparative Example 5, the infrared wavelength selected for the combined treatment had a significant impact on the sterilization effect. When a fumigated solid medium was treated by far-infrared, the surface of the medium was heated slowly and the surface temperature was low. But intermediate-wave infrared was conducive to rapid heating of the medium, the surface temperature was high, and the sterilization effect in combination with the fumigation treatment was better.

EXAMPLE 2

[0040] The dish cover of a medium inoculated with an A. flavus spore suspension of an appropriate concentration was removed, and the medium was placed in a 3 L polypropylene plastic fresh-keeping box. 810 mg of essential oil was accurately weighed and dropped onto filter paper in the box, and the medium in the box was fumigated for 4 h in a constant temperature incubator at 45° C. An infrared drying oven was set to 100° C. and started heating. After the measured temperature on a display was stable, the dish cover was removed, and the fumigated medium was placed on a tray, radiated for 10 min, and then taken out and cooled to room temperature. After the 5.sup.th day of culture, the number of colonies on the medium remained unchanged. Compared with Comparative Example 1, the number of A. flavus spores decreased by greater than 5.65±0.10 log CFU/ml.

[0041] Compared with Example 1, when the infrared radiation temperature was unchanged, the radiation time had a significant impact on the sterilization effect of the combined treatment. Increasing the radiation time increased the surface temperature of the medium and the sterilization effect.

EXAMPLE 3

[0042] The dish cover of a medium inoculated with an A. flavus spore suspension of an appropriate concentration was removed, and the medium was placed in a 3 L polypropylene plastic fresh-keeping box. 810 mg of essential oil was accurately weighed and dropped onto filter paper in the box, and the medium in the box was fumigated for 4 h in a constant temperature incubator at 45° C. An infrared drying oven was set to 110° C. and started heating. After the measured temperature on a display was stable, the dish cover was removed, and the fumigated medium was placed on a tray, radiated for 5 min, and then taken out and cooled to room temperature. After the 5.sup.th day of culture, the number of colonies on the medium remained unchanged. Compared with an untreated group, the number of A. flavus spores decreased by 5.45±0.20 log CFU/ml.

[0043] Compared with Example 1, when the infrared radiation time was unchanged, the radiation temperature had a significant impact on the combined sterilization effect. Increasing the radiation temperature was conducive to rapid heating of the surface of the medium and increased the sterilization effect significantly.

EXAMPLE 4

[0044] The dish cover of a medium inoculated with an A. flavus spore suspension of an appropriate concentration was removed, and the medium was placed in a 3 L polypropylene plastic fresh-keeping box. 810 mg of essential oil was accurately weighed and dropped onto filter paper in the box, and the medium in the box was fumigated for 6 h in a constant temperature incubator at 45° C. An infrared drying oven was set to 100° C. and started heating. After the measured temperature on a display was stable, the dish cover was removed, and the fumigated medium was placed on a tray, radiated for 5 min, and then taken out and cooled to room temperature. After the 5th day of culture, the number of colonies on the medium remained unchanged. Compared with Comparative Example 1, the number of A. flavus spores decreased by 4.75±0.20 log CFU/ml.

[0045] Compared with Example 1, when the infrared radiation conditions were unchanged, the fumigation time had insignificant impact on the combined sterilization effect, and increasing the fumigation time did not significantly improve the sterilization effect.

EXAMPLE 5

A Method for Eliminating A. Flavus Spores from Rice

[0046] Rice inoculated with an A. flavus spore suspension of an appropriate concentration was placed in a 3 L polypropylene plastic fresh-keeping box. 810 mg of essential oil was accurately weighed and dropped onto filter paper in the box, and the rice was fumigated for 4 h in a constant temperature incubator at 45° C. An infrared drying oven was set to 100° C. and started heating. After the measured temperature on a display was stable, the fumigated rice was placed on a tray, radiated for 10 min, and then taken out and cooled to room temperature. The spores were eluted, and after the 5.sup.th day of culture, the number of colonies on a medium remained unchanged. Compared with an untreated group, the number of A. flavus spores decreased by 3.82±0.20 log CFU/ml.

EXAMPLE 6

A Method for Eliminating A. Flavus Spores from Corn

[0047] Corn inoculated with an A. flavus spore suspension of an appropriate concentration was placed in a 3 L polypropylene plastic fresh-keeping box. 810 mg of essential oil was accurately weighed and dropped onto filter paper in the box, and the corn was fumigated for 4 h in a constant temperature incubator at 45° C. An infrared drying oven was set to 110° C. and started heating. After the measured temperature on a display was stable, the fumigated corn was placed on a tray, radiated for 5 min, and then taken out and cooled to room temperature. After the 5th day of culture, the number of colonies on the medium remained unchanged. Compared with an untreated group, the number of A. flavus spores decreased by 4.00±0.20 log CFU/ml.

COMPARATIVE EXAMPLE 1

[0048] A solid medium was inoculated with an A. flavus spore suspension diluted to an appropriate concentration, the spores germinated after being cultured in a constant temperature and humidity incubator at 28° C. and 70% RH for 1 d, and the number of colonies was counted as 7.35±0.12 log CFU/ml.

COMPARATIVE EXAMPLE 2

Infrared Radiation Alone

[0049] A. flavus spores on a solid medium were treated with reference to the method of Example 1. The only difference was that infrared radiation was used alone, and other conditions were the same as those of Example 1. The results were shown in Table 1.

COMPARATIVE EXAMPLE 3

Essential Oil Fumigation Alone

[0050] A. flavus spores on a solid medium were treated with reference to the method of Example 1. The only difference was that essential oil fumigation was used alone, and other conditions were the same as those of Example 1. The results were shown in Table 1.

COMPARATIVE EXAMPLE 4

Infrared Radiation First and then Essential Oil Fumigation

[0051] A. flavus spores on a solid medium were treated with reference to the method of Example 1. The only difference was that the precedence order of essential oil fumigation and infrared radiation was adjusted, and other conditions were the same as those of Example 1. The results showed that the number of A. flavus spores on the surface of the solid medium decreased by 2.40±0.20 log CFU/ml.

COMPARATIVE EXAMPLE 5

Essential Oil Fumigation First and then Far-Infrared Radiation

[0052] A. flavus spores on a solid medium were treated with reference to the method of Example 1. The only difference was that a far infrared drying oven with a wavelength of 5-15 μm was used for heating, and other conditions were the same as those of Example 1. The results were shown in Table 1.

TABLE-US-00001 TABLE 1 Effects of different treatments in killing A. flavus spores on a solid medium Surface Total count temperature of reduction/[log material after CFU/ml or Sample Treatment method treatment log CFU/g] Comparative none 13-16° C. — Example 1 Comparative intermediate-wave 62-65° C. 2.59 ± 0.15 Example 2 infrared radiation Comparative Fumigation 14-15° C. 0.38 ± 0.08 Example 3 Comparative (intermediate-wave) 32-35° C. 2.40 ± 0.20 Example 4 infrared radiation first and then fumigation Comparative Fumigation first and then 57-60° C. 2.80 ± 0.08 Example 5 (far) infrared radiation Example 1 Fumigation first and then 64-67° C. 4.08 ± 0.11 (intermediate-wave) infrared radiation Example 2 Fumigation first and then 68-71° C. 5.65 ± 0.10 (intermediate-wave) infrared radiation Example 3 Fumigation first and then 65-68° C. 5.45 ± 0.20 (intermediate-wave) infrared radiation Example 4 Fumigation first and then 63-66° C. 4.75 ± 0.20 (intermediate-wave) infrared radiation Example 5 Fumigation first and then 62-65° C. 3.82 ± 0.20 (intermediate-wave) infrared radiation Example 6 Fumigation first and then 61-64° C. 4.00 ± 0.20 (intermediate-wave) infrared radiation

[0053] Although the disclosure has been provided as above in preferred examples, it is not intended to limit the disclosure. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure. Therefore, the protection scope of the disclosure should be defined by the claims.