The Aflatoxin produced by peanuts contaminated with Aspergillus flavus has a strong carcinogenic effect on humans and animals. This passage is to guide the prevention and control of peanut aflatoxin and will discuss the effects of contaminated peanut, damage of aflatoxin, removal, and prevention of contaminated peanut.
Peanut is an important economic crop, oil crop and export crop for foreign exchange earning in China. The perennial planting area is close to 5 million hm2, accounting for 20% of the world's total planted area, ranking second in the world. The output is close to 15 million tons, accounting for 40% of the world's total output, ranking first in the world. However, peanuts are often contaminated with Aspergillus flavus and produce aflatoxin (AFT) during field management, harvesting, drying, storage, transportation, and processing to produce aflatoxin (AFT).
Aflatoxin is extremely harmful to human health. Aflatoxin is a strong carcinogen, and its toxicity is 60 times stronger than that of arsenic, and it is extremely harmful to humans and animals. At present, to reduce harm to humans, many countries and international organizations have imposed a strict limit of AFT on the production, export, and import of peanuts and peanut products. Aflatoxin is a toxic substance, a kind of fungal metabolite, with fluorescence reaction produced by Aspergillus fungi in peanut kernels. It is not a single compound, but a group of compounds with very similar chemical structures. At present, at least 18 kinds of aflatoxin have been isolated, which are aflatoxin B, G, and M. The most common varieties are B1, B2, G1, G2, etc. Aflatoxin B1 is the most toxic natural carcinogen found currently. An overview of the effects of contaminated peanut, damage of aflatoxin, removal, and prevention of contaminated peanut is now available.
Infection of Aflatoxin in peanuts
According to the different infection and production time of peanut, the infection can be divided into a pre-harvest infection (developmental pods in the soil are infected by Aspergillus flavus and produce toxin) and post-harvest infection (infected Aspergillus flavus and produces poison during storage and processing). The infection rate varies with environmental factors and the content of moisture in the peanut. The high temperature and low humidity of the soil contribute to the infection and production of Aspergillus flavus. The three main factors affecting the production of mold are temperature, humidity, and oxygen. The growth temperature of molds such as Aspergillus flavus is 10 to 45 ° C, and the suitable temperature of mold in growth is 30 ° C, the suitable temperature for producing toxicity is 24 to 30 ° C. The growth is the fastest with 85% environmental humidity and 12% to 20% content of moisture in the seed. Toxins also require oxygen during their growth.
The harm and impact of aflatoxin
The first harm of aflatoxins is to human beings. Peanut fruit, peanut kernel and peanut oil are the main targets of contamination in Aspergillus flavus . The toxin-producing strain infects peanuts and metabolizes AFT in the seed of kernel, which poses a potential threat to human life after consumption. If you eat food contaminated with AFT, you may have aflatoxin symptoms in having fever, abdominal pain, vomiting, loss of appetite, severe cases of hepatosplenomegaly, liver area pain, skin mucosal yellow staining, ascites, lower extremity edema, dysfunctional liver disease, heart enlargement, pulmonary edema, and even convulsions and coma within 2 to 3 weeks. AFT is also a potential carcinogen that can cause cancers such as human liver cancer.
The second harm is the impact on peanut exports. Peanut is an important oil crop and dominant export agricultural product in China. Where does the peanut come from? China's export of peanuts mainly has come from the northern region. One of the most important reasons is that peanuts produced in the northern region are less infected by AFT. Even so, China's peanuts exported to foreign countries have been repeatedly tested for AFT based on the standard. It causes huge losses to export companies. The AFT has become a limiting factor in peanut exports. The third harm is the impact on the feed. AFT mainly pollutes corn, peanuts, cottonseed and its cakes, which can occur in the field of feed crops in growth and post-harvest storage. Due to the high-temperature resistance of AFT, it is difficult to be destroyed AFT during the processing of compound feed. It results in the compound feed being contaminated by AFT. Besides, the content of moisture in the feed is too high, and the temperature and humidity conditions of the storage environment are not suitable. Their factors are also important reasons for the AFT-contaminated compound feed. When the content of AFT in the feed is greater than 1 mg/kg, the livestock may cause death after consumption.
Method to remove aflatoxin in peanut.
AFT is a strong carcinogen, which seriously threatens the health of humans and animals and has become a serious social hazard. At present, there are mainly methods for removing aflatoxins from peanuts.
The first method is to select molds. The distribution of AFT in peanut is very uneven, and it mainly concentrated in mildew granules, followed by grains of broken, wrinkled, discolored and worms. Most of the seeds contaminated with AFT can be selected and removed by naked eyes.
The second method is the ammonia fumigation. Peanut kernels dyed with AFT, mixed with 15% to 25% ammonia water, or ammoniated with industrial ammonia containing 98% ammonia for detoxification treatment under normal temperature and pressure, sealed fumigation for 2d. It has a good effect on detoxification, and does not affect the oil yield of peanut kernels and does not change the quality.
The third method is the photoelectric rejection. This method is a photoelectric sorting machine that uses a color filter and a photocell to compare the pre-adjusted standard with the broken peanut kernel or the contaminated peanut kernel, and the accuracy is as high as 98%.
The fourth is the physical adsorption method. This method can treat peanut oil contaminated with AFT. Adding toxic peanut oil to the adsorbent such as activated clay and activated carbon, the detoxification effect is remarkable.
The fifth is the heating detoxification method. Peanut oil containing aflatoxin B1 can be detoxified by rapid heating. The rapid heating method is to heat the empty pot to about 200 ° C, put the peanut oil into the pot, continue to heat to the desired temperature, keep the temperature for 3 to 5 minutes and stop heating. The slow heating method means that the peanut oil is placed in the pot at room temperature, heated to the desired final temperature, maintained at the final temperature for a while, and stopped the heating. The method has a good effect on removing toxins, and the color, smell, and taste of the oil are not changed.
The sixth methods are to remove by Litsea cubeb. Through a series of studies on anti-mold and detoxification, it was found that a plant, Litsea cubeb is the buster of Aspergillus flavus. After added the aromatic oil of Litsea cubeb directly to the sample with aflatoxin, all the toxins are eliminated. If the peanut oil is 10 times more than the standard, the aromatic oil can be eliminated.
How do you get rid of aflatoxin in peanuts?
Peanut and peanut products are the main contaminated objects of Aspergillus flavus. How to reduce Aflatoxin infection and AFT pollution has become a growing concern for scholars at home and abroad. People try to explore solutions in multiple ways.
The first method is to breed new peanut varieties with high resistance to Aspergillus flavus. One of the main ways for humans to overcome plant diseases is to use resistant resources that is to cultivate through conventional breeding varieties with resistant to Aspergillus flavus. Given the limitations of pathways in conventional breeding, the complexity of breeding plants with disease resistance, the lack of understanding in the disease mechanism of the plant, breeding plant with disease resistance has always been a major problem in agricultural production. There is no breakthrough in the selection of new peanut varieties with resistant to Aspergillus flavus, but this is the most direct and effective method to avoid infection. It is believed that advanced breeding techniques such as transgenic and molecular marker-assisted selection are expected to breed new varieties with high resistance to Aspergillus flavus shortly. These techniques are to reduce the infection of peanut in Aspergillus flavus and eliminate the harm of Aspergillus flavus to humans.
The second is to control underground pests. Underground pests have a great influence on the infection of Aspergillus flavus in the early stage before harvesting in peanut. Therefore, in the process of peanut in growth, especially after flowering, comprehensive control of underground pests should be adopted to control cockroaches, nematodes, mites, and mites. Measures need to be taken to reduce the number of underground pests in peanut fields to a minimum.
The third is to prevent the peanut pod from rupturing. To prevent artificial damage to the peanut pods, weeding should be done before the injection of the peanuts. Reasonable irrigation and drainage should be carried out to avoid the case of high soil temperature and to prevent the pod from rupturing due to the large difference in temperature.
The fourth is to control temperature and humidity in the soil. This method is to adjust the planting density, maintain the ventilation of the peanut, control temperature in soil, increase and maintain the moisture of soil in the field by 40% to 70% through reasonable irrigation. Appropriate irrigation within 3 to 5 weeks before harvest can prevent peanuts from suffering drought. It can reduce the contamination of Aspergillus flavus by without irrigation in the field, adjusting the growth period, increasing the application of calcium fertilizer and timely harvesting.
The fifth is a timely harvest and rapid drying. In harvest, you should master time in the maturity of peanuts, harvest peanut with good methods and avoid rain harvest. After draining the dry field, the field of peanuts should be plowed as soon as possible, and the peanut should be picked quickly. The peanuts can not be placed in the field for too long. The freshly harvested peanuts should not be stacked. They should be quickly spread and dried, and the content of moisture in the peanut pods should be reduced to the safety rang about Moisture (8% to 9%) or less. During storage of seed, the temperature is controlled below 15 °C and the relative humidity is below 70%.
The sixth method is the use of biocides to fight toxin-producing fungi. According to the principle of the biocide antiviral fungus, the spores of the benign mold are inoculated into the soil spores around the peanut, make it settle in the area of peanut pod. Therefore, the mold becomes a living protective agent against the toxin-producing fungus.