Study On Post-harvest Peanut Aflatoxins Contamination And Risk Assessment In China

Peanut is the major oil crop and predominant agro-product for export and no import in China, whose production ranks the first among all kinds of oilseeds in the country. As the main cash crop used as both food and vegetable oil, peanut plays an important role in China. However, aflatoxin contamination has been threatening consumption safety and international trade during the recent years, and become the grave potential risks to prevent consumption safety and industry development of peanut. Therefore, for aflatoxin contamination in peanut in China, it's important to discover the current contamination and develop risk assessment technology for quality & safety supervision, standards setting & revision and exporting trade of agro-products such as peanuts.In the thesis, the distribution of aflatoxin contamination in post-harvest peanut in China was firstly, systematically researched. Collected from 13 main provinces of peanut production covering 90% of peanut production area in the country, 2571 peanut samples were analyzed with an international advanced method of immuno-affinity-liquid-chromatography. And, of aflatoxin contamination in post-harvest peanut in China, the single and total contaminants, contaminated area distribution and contamination features were discovered. Based on the data of aflatoxins contamination in post-harvest peanut and peanut consumption levels in China, the protocol of risk assessment was developed, comprised of ultra-trace data processing method of aflatoxin contamination in peanut and non-parametric quantitative probabilistic assessment as the nuclear techniques. The developed protocol not only accorded with generic international rules, but also was applicable for aflatoxins contamination in peanut in China. With this protocol, dietary intake risk of aflatoxin in post-harvest peanut in China was assessed. So here provided a key technical support for quality & safety supervision, setting & revising standards, and exporting trade and negotiations of Chinese agro-products such as peanuts.The main research methods and results were summarized as the below.1. For the first time, the distribution of aflatoxin contamination in post-harvest peanut in China was discovered and the database of aflatoxin contamination in peanut was constructed. With a stratified random sampling method, 2571 peanut samples were collected in 2009 and 2010 from the country's main production areas. The samples were detected by the international advanced immunoaffinity-liquid chromatographic method, from which 12855 data of aflatoxin contamination were acquired. The database of aflatoxin contamination in post-harvest peanut in China was developed based on Microsoft.net framework 2.0 and SQLite, which could be written, revised, browsed and searched, input and output data, with the features of few resources occupation and easy maintenance. The database could be conveniently called by @risk to analyze the distribution of aflatoxin contamination in peanut and assess risk assessment of aflatoxin. It was shown that aflatoxin B₁ (AFB₁) is the dominating contaminant in Chinese post-harvest peanuts, averaged 86.2% of the total aflatoixns with a correlation coefficient of 0.99. For aflatoxins contamination levels of post-harvest peanuts, the highest was in Anhui province and the lowest in Liaoning province; the highest in Yangtze River ecological region and the lowest in North-East ecological area, and the results indicated that the aflatoxins contamination levels of post-harvest peanuts in China exhibited apparently regional characteristics, and inferred a tendency that the heavy contamination region has been spreading to north.2. A dietary exposure assessment technique of aflatoxin in peanut in China was developed with the core of ultra-trace data processing method of alternative point value of"0"and"LOD"and non-parametric probability assessment technique. It was proven that the key limit factor on ultra-trace data processing of aflatoxin contamination were aflatoxin analysis method and its limit of detection. After optimization and screening of point value substitute methods such as 0, 1/2 LOD and LOD and of 37 kinds of distribution substitute methods such as Pearson and Lognormal distribution and so on, a constant value method of aflatoxins contamination of 0 and LOD alterative was developed based on the detection method of immunoaffinity-HPLC. And based on the constant value method of 0 and LOD alterative, a non-parametric probability technique was developed. An iterative simulation with 30000 times and sampling with 1000 times were selected after optimization for the non-parametric probability assessment. With the developed non-parametric probability assessment method, the dietary exposure of Chinese post-harvest peanuts was assessed. The result indicated that children belonged to the group with high exposure of aflatoxin in post-harvest peanut, averagely, with 2.06 times of the standard population's dietary exposure of aflatoxin, and that Anhui province belonged to the area with high exposure of aflatoxin in peanut, in which the standard population's dietary exposure dose of aflatoxin in post-harvest peanut was 48.3 and 4.83 times of that of European Union and that of Chinese standards respectively. So it needs more attention during governmental risk management.3. The dietary intake risk of aflatoxin post-harvest peanut in China was assessed with the developed method of risk assessment for aflatoxin in peanut based on the distribution and the database of aflatoxin contamination in post-harvest peanut in China. Among the groups classified by ages, it was the highest of the post-harvest peanut dietary intake risk for the group of persons in middle and old age, over 45 years old. For the persons in middle and old age with positive hepatitis B surface antigen, the average risk value and P97.5 value were 0.1356 cases per 100,000 persons per year and 0.2169 cases per 100,000 persons per year, which were 0.6% and 0.96% of the yearly liver cancer incidence in China. Among the main peanut production provinces, it was the highest of the post-harvest peanut dietary risk for Anhui Province people. For the group of 18⁴5 years old people in Anhui, the average risk value and P97.5 value were 0.1693 cases per 100,000 population per year and 1.932 cases per 100,000 population per year, which were 0.75% and 8.59% of the yearly liver cancer incidence in China. Among the four biggest peanut economic areas, it was the highest of the peanut dietary intake risk in the Yangtze River area. The average risk value and P97.5 value for the group of 18⁴5 years old people in this area were 0.00641 cases per 100,000 persons per year and 0.05977 cases per 100,000 persons per year, which were 0.03% and 0.27% of yearly liver cancer incidence in China.In addition to high-risk groups in individual districts, the dietary intake of aflatoxin in post-harvest peanut in China contributed to liver cancer less than 1% except for the persons with high risk in few districts. The results indicated that the post-harvest peanut dietary risk were low, which caused by peanut production and harvesting process, and that further studies need to be focused on the process of peanut circulation and storage for aflatoxin contamination risk assessment, to clarify main process caused aflatoxin contamination in peanut and to protect peanut consumption safety and export trade.