Corn kernel postharvest storage method based on plant source mildew preventive

Abstract

The invention discloses a corn kernel postharvest storage method based on a plant source mildew preventive. Relates to the technical field of mildew prevention. The invention provides a specific storage method. According to the invention, the plant source mildew inhibitor is prepared by a molecular embedding method, the mildew-proof and fresh-keeping effects of the plant source mildew inhibitor on the postharvest storage of the corn kernels are systematically evaluated, the use technical parameters of the plant source mildew inhibitor in the postharvest storage of the corn kernels are determined, and the postharvest storage method of the corn kernels based on the plant source mildew inhibitor is provided. An efficient and natural solution capable of replacing chemical preservatives is provided for safe storage of the corn kernels, and theoretical innovation and practical popularization value are achieved. According to the method, the quality loss of harvested corn kernels caused by heating and mildewing can be avoided, and the economic benefit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of mildew prevention, and more specifically, to a post-harvest storage method for corn kernels based on plant-derived mildew inhibitors. Background Art

[0002] Corn contains nutrients such as carbohydrates, proteins, fats, vitamins, and minerals. In addition, its embryo is relatively large and has strong hygroscopicity, making it vulnerable to the invasion of harmful molds during post-harvest storage. Especially when the environmental temperature and humidity reach the suitable conditions for mold growth, the harmful molds carried by corn kernels will rapidly grow and reproduce, leading to corn mildew. Mildewed corn not only has a reduced quality but also carries mycotoxins, seriously threatening the lives and health safety of humans and animals. Therefore, adopting a suitable method to inhibit the reproduction of molds during corn storage is crucial for maintaining the good quality of corn and ensuring its safe storage.

[0003] Currently, chemical agents are mostly used in production for mildew prevention treatment of corn. However, chemical agents have a certain toxic accumulation effect on the human body, can cause environmental pollution, and in addition, long-term use leads to the generation of drug resistance in molds. Therefore, it is particularly urgent to develop safe, green, and efficient storage mildew inhibitors. Plant essential oils are a class of secondary metabolites extracted from plants. Due to their broad-spectrum antibacterial properties and easy biodegradability, etc., they have great development value in aspects such as grain mildew prevention and freshness preservation.

[0004] Research shows that after peanut kernels treated with Litsea cubeba essential oil are stored for 20 days at 35 °C and an air humidity of 85%, not only is the mildew rate reduced, but the quality is also improved; after paddy rice with a moisture content of 13% treated with Perilla frutescens essential oil is stored for one month under variable temperature conditions, the total colony count and fatty acid value are lower than those of the untreated ones; 80 μL / 0.25 L of Pulsatilla chinensis essential oil can significantly inhibit the proliferation of fungi and the production of aflatoxin during the storage of mung beans. It can be seen that using plant essential oils in the process of grain storage can prevent grain mildew and, to a certain extent, delay the deterioration of grain quality.

[0005] However, in the actual application process, there are still some problems with directly using plant essential oils for grain storage. For example, plant essential oils are prone to volatilization, have high instability, and the special smell of the essential oils themselves may affect the grain flavor. These problems have hindered the application of plant essential oils in grain storage. Therefore, in actual applications, it is necessary to select a suitable carrier or other methods to delay the volatilization rate of plant essential oils to achieve the purpose of long-term antibacterial and freshness preservation.

[0006] The plant essential oil microencapsulation technology refers to using plant essential oils as the core material and natural or synthetic polymers as the wall material. During the microencapsulation process, the plant essential oils are encapsulated and protected in the wall material, making them less susceptible to the influence of the environment.

[0007] So far, there is a lack of research data on the application of plant essential oil microcapsules in corn storage. Therefore, it is an urgent problem for those skilled in the art to provide a post-harvest storage method for corn kernels based on plant-derived mold inhibitors. Summary of the Invention

[0008] In view of this, the present invention provides a post-harvest storage method for corn kernels based on plant-derived mold inhibitors

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A post-harvest storage method for corn kernels based on plant-derived mold inhibitors, wherein the plant-derived mold inhibitor is evenly mixed into the picked and dried corn kernels, then packaged and stored under constant temperature and humidity conditions;

[0011] The preparation method of the plant-derived mold inhibitor includes the following steps:

[0012] (1) Weigh resistant starch and add it to water, react in a water bath to make an aqueous solution of resistant starch;

[0013] (2) Dissolve cinnamon essential oil in absolute ethanol, and slowly add it drop by drop to the aqueous solution containing resistant starch. This process is still carried out in a water bath. After encapsulation in the water bath, transfer and sediment until complete stratification;

[0014] (3) Then remove the upper clear liquid to obtain wet microcapsules. Spread the wet microcapsules thinly and freeze-dry to obtain dry microcapsules;

[0015] (4) Grind the microcapsules to obtain the plant-derived mold inhibitor.

[0016] Preferably: the dosage of the plant-derived mold inhibitor: w / w is 1% - 3%; the moisture content of the corn kernels w / w is 15%; constant temperature and humidity: the temperature is 30 °C and the relative humidity is 75%; the temperature of water in step (1): 60 °C, the reaction time: 30 min, and the reaction process is sealed with plastic wrap.

[0017] Preferably: the encapsulation time in step (2): 1.5 h; transfer: to an environment of 4 °C and sediment for 48 h.

[0018] Preferably: the freeze-drying time in step (3): 48 h.

[0019] Preferably: the mass ratio of resistant starch to cinnamon essential oil is: 100 g: 50 g.

[0020] According to the above technical solutions, compared with the prior art, the present invention discloses a post-harvest storage method for corn kernels based on plant-derived mold inhibitors, and the technical effects obtained are:

[0021] The present invention prepares a plant-derived mildew-proof agent (cinnamon essential oil-resistant starch microcapsule, RSCEO) by molecular embedding method. By measuring multiple quality indexes such as color, fatty acid value, MDA content, conductivity, and CAT activity, combined with the detection of mildew rate, fungal spore number, fungal diversity, and the contents of AFB1, DON, and ZEN, the mildew-proof and fresh-keeping effect of the agent on post-harvest storage of corn kernels is systematically evaluated, and the technical parameters for its use in post-harvest storage of corn kernels are determined. A method for post-harvest storage of corn kernels based on the plant-derived mildew-proof agent is proposed. This invention provides an efficient, natural and chemical-preservative alternative solution for the safe storage of corn kernels, with both theoretical innovation and practical promotion value.

[0022] According to statistics, the loss rate of corn kernels due to heating and mildew during the post-harvest storage stage is about 8%. This invention can avoid the quality loss of post-harvest corn kernels caused by heating and mildew, and improve economic benefits. Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0024] Figure 1 The drawings are the diagrams showing the change rules of the color of corn kernels in different treatment groups provided by the present invention. Among them, A, B, and C in the figures respectively represent the changes of L*, a*, and b* of corn in different treatment groups during storage. Different letter markings represent that different treatments have significant differences in the color of corn kernels at the same storage time (P < 0.05).

[0025] Figure 2 The drawings are the diagrams showing the change rules of the fatty acid value of corn kernels in different treatment groups provided by the present invention. Among them, different letter markings represent that different treatments have significant differences in the fatty acid value of corn kernels at the same storage time (P < 0.05).

[0026] Figure 3 The drawings are the diagrams showing the change rules of the MDA content of corn kernels in different treatment groups provided by the present invention. Among them, different letter markings represent that different treatments have significant differences in the MDA content of corn kernels at the same storage time (P < 0.05).

[0027] Figure 4 The drawings are the diagrams showing the change rules of the conductivity of corn kernels in different treatment groups provided by the present invention. Among them, different letter markings represent that different treatments have significant differences in the conductivity of corn kernels at the same storage time (P < 0.05).

[0028] Figure 5 The accompanying figure is a graph showing the change pattern of CAT activity in corn kernels of different treatment groups provided by the present invention. Note: Different letter markings indicate that different treatments have significant differences in the CAT activity of corn kernels at the same storage time (P < 0.05).

[0029] Figure 6 The accompanying figure is a graph showing the change pattern of the number of spores in corn kernels of different treatment groups provided by the present invention. Different letter markings indicate that different treatments have significant differences in the number of spores at the same storage time (P < 0.05).

[0030] Figure 7 The accompanying figure is a graph showing the relative abundances of fungal species at the phylum level in corn kernels of different treatment groups provided by the present invention. Among them, CK represents the CK control group, CK-30 represents the CK control group stored for 30 days; S1RS represents the R1 group, S1RS-30 represents the R1 group stored for 30 days; S3RS represents the R3 group, S1RS-30 represents the R3 group stored for 30 days; S1Na- represents the SDA group, S1Na-30d represents the SDA group stored for 30 days.

[0031] Figure 8 The accompanying figure is a graph showing the relative abundances of fungal species at the genus level in corn kernels of different treatment groups provided by the present invention. Among them, CK represents the CK control group, CK-30 represents the CK control group stored for 30 days; S1RS represents the R1 group, S1RS-30 represents the R1 group stored for 30 days; S3RS represents the R3 group, S1RS-30 represents the R3 group stored for 30 days; S1Na- represents the SDA group, S1Na-30d represents the SDA group stored for 30 days.

[0032] Figure 9 The accompanying figure is a graph showing the change pattern of AFB1 content in corn kernels of different treatment groups provided by the present invention. Different letter markings indicate that different treatments have significant differences in the AFB1 content of corn at the same storage time (P < 0.05).

[0033] Figure 10 The accompanying figure is a graph showing the change pattern of DON content in corn kernels of different treatment groups provided by the present invention. Different letter markings indicate that different treatments have significant differences in the DON content of corn at the same storage time (P < 0.05).

[0034] Figure 11 The accompanying figure is a graph showing the change pattern of ZEN content in corn kernels of different treatment groups provided by the present invention. Different letter markings indicate that different treatments have significant differences in the ZEN content of corn at the same storage time (P < 0.05). Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] An embodiment of the present invention discloses a post-harvest storage method for corn kernels based on a plant-derived mildew-proof agent.

[0037] In the embodiment, raw materials not mentioned are all commercially available, and methods not mentioned are all conventional processes. For example, resistant starch (as the wall material) is purchased from Shandong Ruifan Biotechnology Co., Ltd.; cinnamomum essential oil (as the core material) is purchased from Ji'an Zhongxiang Plant Co., Ltd.

[0038] Example 1

[0039] A post-harvest storage method for corn kernels based on a plant-derived mildew-proof agent, wherein the preparation method of the plant-derived mildew-proof agent (cinnamomum essential oil-resistant starch microcapsule, i.e., RSCEO) includes the following steps:

[0040] (1) Weigh 100 g of resistant starch and add it to water at 60 °C, react in a water bath for 30 min, and seal the reaction process with plastic wrap to prepare a resistant starch aqueous solution;

[0041] (2) Dissolve 50 g of cinnamomum essential oil in absolute ethanol, and slowly add it drop by drop to a conical flask containing the resistant starch aqueous solution. This process is still carried out in a water bath. After embedding in the water bath for 1.5 h, transfer it to a 4 °C refrigerator and sediment for 48 h to ensure complete stratification;

[0042] (3) Subsequently, use a pipette gun to remove the upper clear liquid to obtain wet microcapsules. Spread the wet microcapsules thinly and flatly in an aluminum box, with a height not exceeding 1 / 2 of the aluminum box, and place it in a vacuum freeze dryer (CTFD-10T, Qingdao Yonghe Chuangxin Electronic Technology Co., Ltd.) for freeze-drying for 48 h to obtain dry microcapsules;

[0043] (4) Place the microcapsules in a mortar and grind them to obtain a plant-derived mildew-proof agent, which is in powder form.

[0044] Comparative experiment

[0045] Pretreatment of corn kernels

[0046] Take corn kernel samples with a moisture content of 15% (w / w), pack them into bags at 1.5 kg per bag, store them in a constant temperature and humidity incubator at a set temperature of 30 °C and a relative humidity of 75% for 180 d, take samples every 30 d, and take three parallel samples each time.

[0047] Negative control group: No treatment was performed, named as the CK group.

[0048] Positive control group: Sodium diacetate was uniformly mixed into the corn kernel samples at an addition amount of 1% (w / w), named as the SDA group.

[0049] Treatment of the experimental group: RSCEO (mentioned in Example 1) was uniformly mixed into the corn kernel samples in self-sealing bags at addition amounts of 1% (w / w) and 3% (w / w) respectively, and they were named as the R1 group and the R3 group respectively.

[0050] Determination of the color of corn kernels during postharvest storage

[0051] Approximately 50 g of corn kernel samples were randomly selected, and the L*, a*, and b* values of the corn kernels were measured using a color difference meter. The color change of the corn kernels during postharvest storage is as Figure 1 shown ( Figure 1 in which L* represents lightness. The brighter the color of the corn kernels, the larger the value; the darker the color, the smaller the value. a* represents the red-green value, and a positive a value indicates red. The redder the color of the corn kernels, the larger the value. b* represents the yellow-blue value, and a positive b value indicates yellow. The yellower the color of the corn kernels, the larger the value).

[0052] Figure 1 The overall trend shows that as the storage time extends, the L* values of the corn kernels in all treatment groups gradually decrease, and the a* and b* values also show fluctuations to varying degrees. When stored for 30 d and 60 d, the L* values of the corn in the R1 and R3 groups were significantly higher than those of the CK control group (P < 0.05), indicating that the treatment with RSCEO can delay the decrease in the lightness of corn kernels to a certain extent. When stored for 180 d, the L* value of the corn kernels in the R1 treatment group was significantly higher than that of other groups, indicating that 1% (w / w) of RSCEO has a positive effect on maintaining lightness. In addition, when the corn kernels in the R1 group were stored for 180 d, the L* value and the b* value were significantly different from those of the SDA group (P < 0.05), indicating that adding 1% RSCEO is superior to the treatment with 1% sodium diacetate in maintaining the color of corn kernels.

[0053] Determination of the fatty acid value of corn kernels during postharvest storage

[0054] The fatty acid value of the corn kernels was determined according to the method described in GB / T 20570-2015. The change in the fatty acid value of the corn kernels during postharvest storage is as Figure 2 shown.

[0055] With the extension of storage time, the fatty acid values of corn kernels in the four treatment groups showed an upward trend. According to the GB / T20570-2015 Rules for Judging the Storage Quality of Corn, when the fatty acid value (KOH / dry basis) does not exceed 65 mg / 100 g, the corn quality is stable and belongs to the first-class high-quality storage grade; when the fatty acid value (KOH / dry basis) is between 65 mg / 100 g and 78 mg / 100 g, the corn quality reaches the critical state, is slightly unsuitable for storage, and belongs to the second-class critical storage grade; when the fatty acid value (KOH / dry basis) exceeds 78 mg / 100 g, the corn quality reaches a significant deterioration state, is severely unsuitable for storage, and belongs to the third-class deteriorated storage grade. In view of this standard, within 60 days of storage, the corn in the CK control group was in a suitable storage state, reached a slightly unsuitable storage state at 90 days of storage, and reached a severely unsuitable storage state at 150 days of storage; for the corn in the R1 and R3 groups, the fatty acid values were always in a suitable storage state within 90 days of storage, and from 120 days of storage to the end of the storage period, the fatty acid values were in a slightly unsuitable storage state. At 180 days of storage, there were significant differences in the fatty acid values between the R1 and R3 groups and the CK control group (P<0.05), indicating that adding RSCEO could effectively inhibit the fat decomposition reaction of corn, delay the deterioration of corn quality, and extend the safe storage period; the corn in the SDA group was in a suitable storage state within 60 days of storage, reached a slightly unsuitable storage state at 90 days of storage, and reached a severely unsuitable storage state at 120 days of storage. In addition, there were significant differences in the fatty acid values between the R1 group and the SDA group throughout the storage period (P<0.05), and these differences further confirmed the potential advantages of RSCEO in slowing down the fat decomposition during corn storage.

[0056] Determination of MDA Content in Corn Kernels during Postharvest Storage

[0057] The MDA content of corn was determined by a conventional method: The corn kernels were ground into powder, and a corn flour sample (1.00±0.01 g) was weighed and thoroughly mixed with 5 mL of 10% trichloroacetic acid (TCA) solution. The centrifuge was set at 4 °C and 1000 r / min for 10 min. The supernatant was collected and fixed to 7 mL with the same concentration of TCA solution. 2 mL of the fixed solution was taken and reacted with an equal volume of 0.6% thiobarbituric acid (TBA) reagent. After heating in a water bath at 100 °C for 15 min, the reaction was immediately terminated by ice bath. After the reaction solution was centrifuged twice (4 °C, 1000 r / min, 10 min), the supernatant was taken to measure the absorbance values at three wavelengths of 450 nm, 532 nm, and 600 nm with a UV-visible spectrophotometer.

[0058] The change in the MDA content of corn kernels during postharvest storage is as follows Figure 3As shown in the figure. With the extension of storage time, the MDA content in each treatment group showed an upward trend and was positively correlated with the storage time (P<0.05). At the same storage time, the MDA content in the CK control group was higher than that in the experimental groups added with RSCEO and sodium diacetate, and there were significant differences (P<0.05). Specifically, from 30 d to 180 d of storage, there were significant differences in the MDA content between the R1 and R3 treatment groups and the CK control group (P<0.05), indicating that adding RSCEO could inhibit the lipid peroxidation reaction of corn, delay the damage of the adverse environment to the cell membrane of corn kernels, and improve the storage tolerance of corn.

[0059] Determination of the electrical conductivity of corn kernels during postharvest storage

[0060] Twenty intact and undamaged corn kernels were selected, washed three times with distilled water, and the weight of the corn kernels was measured after drying the surface moisture of the corn kernels with filter paper. Then they were put into a conical flask containing 50 mL of distilled water. 50 mL of distilled water without corn samples was used as the control group, sealed with plastic wrap, and left standing at 25 °C for 24 h. The electrical conductivity was measured with a conductivity meter.

[0061] The changes in the electrical conductivity of corn kernels during postharvest storage are as Figure 4 shown. From Figure 4 it can be seen that the electrical conductivity of different treatment groups showed an upward trend. From 120 d to the end of the storage period (180 d), the electrical conductivity of the R1 and R3 groups was significantly lower than that of the CK control group (P<0.05), indicating that adding RSCEO could maintain the electrolyte balance inside the corn kernel cells to a certain extent and effectively protect the integrity of the corn kernel cell membrane. The electrical conductivity of the R1 treatment group was significantly lower than that of the SDA group (P<0.05), indicating that adding 1% RSCEO was superior to 1% sodium diacetate in protecting the corn kernel cell membrane.

[0062] Determination of the CAT activity of corn kernels during postharvest storage

[0063] The determination of catalase activity was carried out using a CAT kit (kit number: BC0200, Solarbio, Beijing). The initial absorbance value A1 at 240 nm and the absorbance value A2 after 1 min were recorded, and A = A1 - A2 was calculated. The CAT activity (U / g) = 678 × A ÷ W, where W is the sample mass.

[0064] The changes in the CAT activity of corn kernels during postharvest storage are as Figure 5As shown in the figure. With the extension of storage time, the CAT activity of each treatment group showed a downward trend, indicating that the antioxidant capacity of corn gradually weakened during storage. At 180 days of storage, there were significant differences in CAT activity between the R1 and R3 groups and the CK control group (P<0.05), indicating that RSCEO treatment could effectively maintain the antioxidant capacity of corn. In addition, from 90 days to 180 days of storage, there were significant differences in CAT activity between the R1 group and the CK group (P<0.05), indicating that 1% RSCEO treatment could effectively delay the decline of CAT activity in corn. By RSCEO treatment, the decline of CAT activity in corn could be effectively delayed, thereby slowing down the impact of oxidative stress on the quality of corn and extending its storage period.

[0065] Determination of the moldy rate of corn kernels during postharvest storage

[0066] Randomly select 100 corn samples, and stipulate that the corn with mildew spots is moldy corn. The moldy rate is the proportion of the number of moldy corn samples to the total number of corn samples.

[0067]

[0068] The changes in the moldy rate of corn kernels during postharvest storage are shown in Table 1. It can be seen from Table 1 that the moldy rate of corn in each treatment group was in a continuous growth state during the entire 180-day storage period. During the entire storage period, the moldy rate of the CK control group was significantly higher than that of the R1 and R3 groups (P<0.05), indicating that adding RSCEO could reduce the mildew risk by inhibiting microbial proliferation during this period. At 60 days of storage, the moldy rate of the R3 group was slightly lower than that of the R1 group, but the difference was not significant (P>0.05); after 120 days, there was a significant difference in the moldy rate between the R3 group and the R1 group, which may be due to the fact that the mildew-proof effect of RSCEO did not show a concentration dependence in the initial stage of storage. From 30 to 150 days of storage, the moldy rate of the SDA group was significantly higher than that of the R1 group (P<0.05), indicating that adding 1% RSCEO had a better inhibitory effect on the moldy rate than the conventional mildew-proof agent sodium diacetate.

[0069] Table 1 Variation law of the moldy rate of corn kernels in different treatment groups (unit: %)

[0070]

[0071]

[0072] Note: Different letter markings represent significant differences in the moldy rate of corn among different treatments at the same storage time (P<0.05).

[0073] Determination of the number of fungal spores in corn kernels during postharvest storage

[0074] The number of fungal spores in the corn kernel samples was determined according to the method described in the national grain industry standard LS / T 6132-2018. Accurately weigh 10.0 ± 0.1 g of corn kernel samples and place them in a 50 mL stoppered test tube. Add 30 mL of sterile distilled water, place it in a rotary shaker and shake for 1 min at a frequency of 135 times / minute. Then filter it through a 300-mesh nylon filter cloth, place the filtrate in a sterile centrifuge tube, and observe the number of stored grain fungal spores in the corn kernel samples under a microscope using a hemocytometer.

[0075] According to the safety evaluation of the number of fungal spores formulated in the national grain industry standard LS / T 6132-2018, when the number of fungal spores does not exceed 1.0×10 5 (CFU / g), it indicates that there is basically no harmful fungi growing on the surface of the corn and it is in a safe state; when the number of fungal spores is between 1.0×10 5 -9.9×10 5 (CFU / g), there may be a musty smell on the surface of the corn, and it is in the critical state of the key control area; when the number of fungal spores is between 1.0×10 6 -9.9×10 6 (CFU / g), there may be mildew spots on the surface of the corn, and it is in a harmful state; when the number of fungal spores > 1.0×10 7 (CFU / g), it is in a severely harmful state. The change in the number of fungal spores in corn kernels during post-harvest storage is as Figure 6 shown. During the entire storage period, the number of corn kernel spores is in a continuous upward state, indicating that fungi are continuously proliferating during storage. The number of spores in the CK control group increased from 3.9×10 5 CFU / g at 0 d to 1.7×10 6 CFU / g at 180 d, and it was in the critical state of the key control area at 120 d of storage; the number of corn spores in the R1 group and the R3 group increased from 3.9×10 5 CFU / g at 0 d to 9.96×10 5 CFU / g, 9.54×10 5 CFU / g at 180 d, and it has been in the critical state of the key control area during the 180 d of storage; the SDA group increased from 3.9×10 5 CFU / g at 0 d to 8.95×10 5 CFU / g at 180 d, and it has been in the critical state throughout the storage period. During the entire storage process, the number of spores in the CK control group was significantly higher than that in the R1 and R3 groups (P < 0.05), and RSCEO may inhibit fungal proliferation by inhibiting the germination of fungal spores or the growth of hyphae. The number of spores in the R3 group was significantly lower than that in the R1 group (P < 0.05), indicating that the antibacterial effect of RSCEO has a strong concentration dependence of use.

[0076] Determination of fungal diversity in corn kernels during post-harvest storage

[0077] The collection information of the fungal diversity on the surface of corn kernel samples is shown in Table 2.

[0078] Table 2 Sample collection information of fungal diversity on the surface of corn kernels

[0079]

[0080] First, DNA was extracted from the corn kernel samples, and the extracted genomic DNA was detected by 1% agarose gel electrophoresis. The DNA was PCR amplified using the primers SSU0817F (5’-TTAGCATGGAATAATRRAATAGGA-3’) and 1196R (5’-TCTGGACCTGGTGAGTTTCC-3’). The PCR products were detected and quantified using the QuantiFluor TM -ST blue fluorescence quantification system (Promega), and then sequenced using the Illumina Miseq PE300 platform. The sequenced data was assembled, and at the same time, the sequence quality was controlled and filtered. After distinguishing the samples, OTU clustering analysis and species taxonomic analysis were performed.

[0081] The fungal diversity on the surface of corn kernels during postharvest storage was analyzed, and 16 phyla, 33 classes, 46 orders, 60 families, 62 genera, and 69 species of fungi were identified. The experimental results are as Figure 7 、 Figure 8 shown. The surface fungal diversity of the initial corn samples CK control group without storage was analyzed. At the phylum level, it was mainly Ascomycota (97.32%) and Phragmoplastophyta (1.76%). There were 4 genera with relatively high abundances, namely Aspergillus (23.01%), Fusarium (35.45%), unclassified_o__Eurotiales (13.93%), and norank_o__Hypocreales (20.92%). As the storage period extended, the proportion of Ascomycota at the phylum level gradually increased, reaching up to 98.46% after 180 days of storage. At the genus level, the proportion of Aspergillus gradually increased, and after 180 days of storage, the proportion of Aspergillus reached up to 87.86%.

[0082] During the storage of the corn samples in Group R1, the dominant phyla were Ascomycota and Phragmoplastophyta at the phylum level. When stored for 180 days, the proportion of Ascomycota decreased (71.91%), while the proportion of Phragmoplastophyta increased (28.69%). There were three genera with relatively high relative abundances: Fusarium (70.82%), Aspergillus (0.22%), and norank_c__Embryophyta (28.70%). The genus Fusarium was the dominant surface genus in the corn samples of Group R1 after storage for 180 days. During the storage of the corn samples in Group R3, the fungal diversity was similar to that of the corn samples in Group R1 at the phylum and genus levels. After storage for 180 days, at the phylum level, the proportion of Ascomycota mainly decreased (74.49%), and the proportion of Phragmoplastophyta increased (22.08%). There were four genera with relatively high relative abundances: Fusarium accounted for 3.08%, Aspergillus accounted for 4.97%, norank_c__Embryophyta accounted for 22.08%, and norank_o__Hypocreales accounted for 65.35%. Compared with the CK control group (87.86%), the proportion of Aspergillus on the surface of the corn samples with added RSCEO decreased (0.22% in Group R1 and 4.97% in Group R3), indicating that RSCEO could effectively inhibit the growth of Aspergillus fungi on the surface of corn. During the storage of the corn samples in Group SDA, the dominant phyla were Ascomycota and Phragmoplastophyta at the phylum level, accounting for 92.54% and 3.1% respectively after storage for 180 days. There were four genera with relatively high relative abundances: Fusarium (21.10%), Aspergillus (24.74%), unclassified_o__Eurotiales (16.31%), and norank_o__Hypocreales (27.89%). The proportion of Aspergillus on the surface of the corn samples with added RSCEO (0.22% in Group R1 and 4.97% in Group R3) was lower than that of the corn samples in Group SDA (24.74%). The inhibitory effect of RSCEO on the growth of Aspergillus fungi was better than that of sodium diacetate.

[0083] Determination of AFB1, DON, and ZEN Contents in Maize Grains during Postharvest Storage

[0084] The contents of AFB1, DON, and ZEN in corn kernel samples were determined by enzyme-linked immunosorbent assay according to Chinese national standard GB 5009.22-2016. The changes in the contents of AFB1, DON, and ZEN in corn kernels during post-harvest storage are as shown in Figure 9 , Figure 10 , Figure 11 .

[0085] As shown in Figure 9 , with the extension of storage time, the AFB1 content in corn kernels of the four treatment groups showed an upward trend, and there were significant differences in the inhibitory effects of different treatments on AFB1 accumulation. The national standard GB 2761-2017 in China stipulates that the limit index of AFB1 in corn is 20 μg / kg. The AFB1 content in the CK control group was in line with the national standard within 60 days of storage. The AFB1 content in the R1, R3, and SDA groups of corn was in line with the national standard within 90 days of storage at 30 °C. After 30 days of storage, the AFB1 content in the R1 and R3 groups of corn was significantly lower than that in the CK control group (P<0.05). In addition, for the corn in the R1 and R3 groups, although there was no significant difference in the AFB1 content within 0-90 days (P>0.05), during the storage period of 120-180 days, the AFB1 content in the R3 group of corn was significantly lower than that in the R1 group (P<0.05), indicating that the addition of RSCEO can effectively inhibit the production of aflatoxin in corn, and the antibacterial effect increases with the increase of concentration, which is positively correlated with the use concentration of RSCEO.

[0086] As shown in Figure 10 , with the passage of storage time, the DON content in corn kernels of the four treatment groups showed an upward trend, and there were significant differences in the inhibitory effects of different treatments on DON accumulation. The national standard GB 2761-2017 in China stipulates that the limit index of DON in corn is 1000 μg / kg. The DON content in the CK control group of corn exceeded the national limit standard after 90 days of storage; the DON content in the R1, R3, and SDA groups of corn exceeded the national limit standard after 120 days of storage. In addition, starting from the 30th day, the DON content in the R1, R3, and SDA groups of corn was significantly lower than that in the CK control group, and the DON content in the R3 group of corn was significantly lower than that in the R1 group (P<0.05), indicating that the addition of RSCEO can inhibit the production of vomitoxin to a certain extent, and this effect is positively correlated with the use concentration of RSCEO.

[0087] As shown in Figure 11As shown, for the corn kernels stored at 30°C for 180 days, the ZEN content in each treatment group showed an upward trend, and there were significant differences in the inhibitory effects of different treatments on ZEN accumulation. The national standard GB 2761-2017 in China stipulates that the limit index of ZEN in corn is 60 μg / kg. During the 60-day storage period of the CK control group of corn, its ZEN content met the national standard. The ZEN content of the corn in the R1, R3, and SDA groups met the national standard during the 90-day storage period. In addition, starting from the 30th day, the DON content of the corn in the R1 and R3 groups was significantly lower than that of the CK control group, and the ZEN content of the corn in the R3 group was significantly lower than that of the R1 group (P<0.05), indicating that the addition of RSCEO can inhibit the production of ZEN to a certain extent, and this effect is positively correlated with the use concentration of RSCEO.

[0088] The various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0089] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A post-harvest storage method for corn kernels based on plant-derived mildew inhibitors, characterized in that, The plant-derived mildew preventive is evenly mixed into the corn kernels after picking and drying, and then packaged and stored under constant temperature and humidity conditions; the preparation method of the plant-derived mildew preventive includes the following steps: (1) Weigh resistant starch and add it to water, and react in a water bath to make an aqueous solution of resistant starch; (2) Dissolve cinnamon essential oil in absolute ethanol, and slowly add it drop by drop to the aqueous solution containing resistant starch. This process is still carried out in a water bath. After encapsulation in the water bath, transfer it and let it settle until it is completely stratified; (3) Then remove the upper clear liquid to obtain wet microcapsules. Spread the wet microcapsules thinly and freeze-dry them to obtain dry microcapsules; (4) Grind the microcapsules to obtain the plant-derived mildew preventive.

2. The post-harvest storage method of corn kernels based on plant-derived mildew inhibitors according to claim 1, characterized in that, The dosage of the plant-derived mildew preventive: w / w is 1% - 3%; the moisture content of the corn kernels w / w is 15%; constant temperature and humidity: the temperature is 30 °C and the relative humidity is 75%; the temperature of the water in step (1): 60 °C, the reaction time: 30 min, and the reaction process is sealed with plastic wrap.

3. The post-harvest storage method of corn kernels based on the plant-derived mildew preventive agent according to claim 2, characterized in that, The encapsulation time in step (2): 1.5 h; the transfer: to a 4 °C environment and settle for 48 h.

4. The post-harvest storage method of corn kernels based on the plant-derived mildew-proof agent according to claim 3, wherein The freeze-drying time in step (3): 48 h.

5. The post-harvest storage method of corn kernels based on the plant-derived mildew preventive agent according to claim 4, characterized in that, The mass ratio of the resistant starch to the cinnamon essential oil is: 100 g: 50 g.

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