Aflatoxin Contamination and Research in China

Aflatoxins(AF) are highly poisonous secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus.They have been found in moldy human food and animal feeds and have been implicated in numerous animal disorders.A. parasiticus produces four major aflatoxins: B1 , B2 , G1 and G2 , while AFB1 is the most toxic in the group and the toxicity is in the order of B1 > G1 > B2 > G2.Since the 1960 outbreak of Turkey X disease, when more than 10,000 turkeys died after being fed with aflatoxin contaminated peanut meal, scientists in China have paid more attention to the studies on aflatoxins including its distribution, pollution, health hazards, testing, monitoring, detection technology, managing, microbiology, ecology, toxicology, and policies in controlling aflatoxins.In this review, we present a brief report on the situation of aflatoxin contamination and research progress in China. Distribution of aflatoxin contamination The distribution in cereals, oils and foodstuffsIn general, the nationwide aflatoxin contamination was mainly in cereals, oils and foodstuffs.The aflatoxin B1 (AFB1) content detected in vegetable oil products was far higher than in food products.Based on 1,000 investigations of susceptible aflatoxin contamination from nearly 20 provinces between 2002 and 2008, contamination was reported in almost every province.The majority of the samples tested shows the presence of aflatoxins.The overall level of contamination in southern part of China is higher than in the northern region.The most severe province is Guangxi.The main reason is due to the hot and humid southern climate.Climatic condition significant influences the level of aflatoxin contamination.When in serious drought and/or high temperature conditions, or when the soil humidity is below the normal level before harvest, it increase in the number of A. flavus spores in the air resulting more fungal infection, and thus high level aflatoxin accumulation.During end processing and packaging, storage of animal-derived food, "cold chain" transfer or pollution of the packing material could also lead to the A. flavus infection and aflatoxin contamination (Duan et al., 2009). www.intechopen.com Aflatoxins -Detection, Measurement and Control 22Studies on the level of aflatoxin B1 in 486 foodstuff and 146 oil samples collected from 18 cities in 2008 (Zhang, 2008) demonstrated that the levels of aflatoxin contamination were between 0.02 and 54.20 μg/kg in foodstuff and 0.41 and 36.54 μg/kg in oil products respectively.While the detection rate ranged from 0.41％ to 2.06％, respectively.A similar study in 2004 reported that the aflatoxin B1 detection rate was as high as 58％ in 17 grain samples, which was the most severe incidence in Guangxi province (Wang, 2004).Samples collected from 5 provinces including Sichuan (mainly in Chongqing), Guangdong, Guangxi, Hubei and Zhejiang showed that the aflatoxin B1 detection rates were 70.27％ and 24.24％ in corn and peanut respectively (Liu, 2006).The aflatoxin B1 detection rates in peanut oil, peanut and corn samples collected from Yunnan province were 100％, 24.32％ and 5.26％ respectively.The aflatoxin levels in samples were 16.05％ above the legally allowed limit, which was similar to the level in peanut samples from Beijing (Wei, 2002;Gao et al., 2007) . Distribution in dairy productsThe investigation of aflatoxin contamination in dairy products indicated that aflatoxin M1 (AFM1), a hydroxylated metabolite of AFB1 secreted in milk, was commonly detectable in most of the dairy samples tested.This phenomenon is correlated well with the distribution of AFB1.From a survey of more than 1,000 samples in 17 provinces between 1991 and 2005, the following reported detection rate ranged from 4.0% to 73.7%.The scientists of Guangxi Anti-Epidemic and Basic Course Section monitored the AFM1 contamination in 100 samples of milk and dairy products in 15 provinces between 1991 and 1999，the AFM1 contamination levels in milk were from 0.2 μg/kg to 1.9 μg/kg (Tang, 1999a).In 1991, a study using the HPLC on 57 milk samples and 15 milk powder samples from Shanghai，the detection rate of AFM1 were 26.7％ and 73.7％, respectively (concentration ranges between 0.025 and 0.95 μg/kg (Zhu, 1991).A similar survey was performed using TLC in 1995 on 59 milk and 53 milk powder samples from Fuzhou，reported that the detection rates were 4.0％ and 13.19％ respectively (concentration range between 0.06 and 0.20g/kg (Lin, 1995).The data indicated that the detection ratio of AFM1 correlate with the high content of AFB1 in animal feed.The amount of AFB1 consumption by animals influences the amount of AFM1 secreted in milk in a dose-dependent manner.Again, the highest level was detected in milk and dairy products from Guangxi province. Distribution in feedThe investigation of aflatoxin contamination in animal feed demonstrated the wide distribution of aflatoxins.A survey done in more than 1,000 samples in 20 provinces from 2003 to 2008 showed that aflatoxins present in most of the samples, as stated below.This analysis indicated that the general level of serious contamination in southern region is similar to that in northern region.Irradiation has been suggested as a possible means of controlling insects and microbial populations in stored food under moist storage condition (Xiao et al., 2007).Aflatoxins in feeds has long been a problem in Huanan, Huabei and Huazhong large geographic regions.Detections of AFB1 in 109 samples showed that the aflatoxin detectable rate and the average content were 83.9％ and 24.6μg/kg in corn, 100％ and 8.27μg/kg in complete feed, 100％ and 6.81μg/kg in animal and plant protein, 100％ and 13.3μg/kg in www.intechopen.com