The prevention and control of mycotoxins in Thailand
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Mycotoxins research in Thailand during the 10 years has concentrated on aflatoxin with particular reference to maize and peanuts. Maize is the second crop next to rice which is mainly produced for export purposes. The aflatoxin content has become a mayor factor affecting the export of maize in a recent years. At present, such problem seems to be under control after the Government of Thailand has brought the problem into focus in local traders and provided more support in both management and technical aspects.
INCIDENCE OF AFLATOXIN CONTAMINATION IN THAILAND
Based on the testing of 90 samples pre-harvest aflatoxin contamination of maize was found to be negligible in five Thai provinces from 1980 to 1983. A recent joint Department of Agriculture-UK based on 46 maize samples collected from two provinces during the major harvest period in the 1985 rainy season, confirms this low incidence of pre-harvest contamination, where a mean total aflatoxin content of less than 4 ppb and a range of 0 to 27 ppb. were found. Interestingly, most of the 46 batches monitored at harvest had been dried in the field from one to four weeks, but this did not result in any significant aflatoxin contamination. In the rainy season of 1986, a zero level of aflatoxin contamination has been detected from 4 experiment plots in 3 provinces, according to the "On-Farm Testing Program" run by Kasetsart University researchers.
Storage of undried ears, especially temporary farm storage for one to six weeks before the crop is sold, has been identified as the significant source of initial contamination. A mean aflatoxin content of 45 ppb with a range of 10 to 95 ppb was found in ten samples of freshly shelled maize in 1984, and an aflatoxin level of 74 ppb, with a range of 3 to 299 ppb, was found in 19 samples from two provinces in 1985. Effective aflatoxin control measures are needed soon after harvest, preferably within 48 hours. Although the critical initial contamination occurs during ear storage, high levels of aflatoxin contamination are usually associated with delays due to incidence of rain during sun drying, and in transportation or storage systems of either undried or partially dried grain.
All new aflatoxin research is coordinated by the National Committee on Mycotoxin Control in Agricultural Commodities and its three subcommittees, which cover the areas of research and development, extension and marketing. The committee is composed of representatives drawn from both the private sector and the government, including the Cooperatives Promotion Department, Office of Agricultural Economics, Department of Agriculture, Department of Agricultural Extension, Department of Foreign Trade, Board of Trade of Thailand, Bank of Agriculture and Agricultural Cooperatives and the National Economic and Social Development Board.
The duties and responsibilities of the committee are to:
STUDY ON THE ENVIRONMENTAL CAPABILITY OF THE PATHOGEN FOR AFLATOXIN PRODUCTION IN MAIZE
The experiment was conducted to determine the effects of various times and moisture contents on aflatoxin levels in storage conditions. The results indicated that after one week and two weeks 35 ppb and 25 ppb of aflatoxin were detected at the levels of 26, 30% and 14% of moisture content respectively. However, after one month of storage no aflatoxin was detected at 11 % moisture content.
METHODS OF PREVENTING AFLATOXIN
Method of preventing aflatoxin were studied including mechanical drying, chemical treatment and planting time.
A Batch Type system has been tested and found that this method is practical. However, the drying process is slow while batches of maize grain should be placed in the dryer within 48 hours.
Only ammonia and a mixture of ammonium polypropionate and propionic acid at a ratio of 8: 2 were economically effective in preventing aflatoxin contamination.
Maize can be planted all year round but harvesting time should coincide with dry season to avoid aflatoxin contamination.
Leaving mature maize in the field for 2-4 weeks before harvesting has proved that aflatoxin formation was minimised. This method enhanced the reduction on costs for drying. The second crop could be grown immediately after cutting off the top.
PRACTICAL APPLICATIONS OF RESEARCH RESULTS
Results from a joint project between the government and private sectors on prevention of aflatoxin maize at Amphur Phayuhakiri, Nakhon Sawan Province are as follows:
Delaying the Time of Maize Cultivation to Avoid Aflatoxin Contamination
Soybean was planted in May, 1986. After harvesting soybean, maize was planted in August. Aflatoxin prevention in maize was successful because maize was harvested in December when the moisture content was relatively low (i.e. < 14%) due to recent drought.
The experiments to control aflatoxin were conducted by drying 18 tons of maize grains for 3 hours in 3 times. The results showed that the moisture content of seeds was 30-32% before drying and 13-16% after drying. No increase in aflatoxin content was detected before and after the drying phase.
Sixty metric tons of maize seed treated with ammonium polypropionate + propionic acid in a ratio of 8:2 under 22:25% relative humidity showed no increase in aflatoxin content during the 6 weeks post treatment.
A training program for aflatoxin control was organized for officers from the Agricultural Extension Department, the Bank of Agriculture and Agricultural Cooperatives, Department of the Cooperative promotion, as well as representatives from the Thai Maize and Produce Traders Association.
The recommendations for aflatoxin monitoring and control were published and distributed to farmers, local dealers and exporters, etc.
The addition to the control of aflatoxin in Agricultural Food Commodities level of toxin contamination was established by the Food and Drug Adminstration (FDA) of Thailand. According to the relevant notification of the Ministry of Public Health prescribed by virtue of Food Act B.E. 2522 (1979), foods shall not contain any microbiological toxin or metabolic products in a manner that may be harmful to health. The maximum allowed level of aflatoxin in oil, fat, peanut oil and coconut oil is 20 ug/kg.
In respect to commodities for export, the level of aflatoxin may follow any requirement (imposed by the importing country), which might also be aligned with the standard level recommended by the Codex Committee on food additives.
Aflatoxin analysis is routinely done at a number of laboratories in Thailand. Unfortunately, sampling methods, sample preparation and analytical methods vary widely, although efforts are being made to standardise them. Inspection companies offer an aflatoxin analysis service that is predominantly semiquantitative, based on minicolumn determination which is sometimes linked to a fluorotoxin meter. Fully quantitative aflatoxin determination is mainly performed in government laboratories, using quantitation by thinlayer chromatography (TLC). Sophisticated techniques, such as high-performance liquid chromatography (HPLC) and high-performance thin-layer chromatography (HPTLC), are being introduced.
Future research has been approved by the national committee in the areas of:
Much of the aflatoxin research in Thailand can now be considered to be coordinated and cooperative, due to the influence of the national committee. Assistance from other countries to provide funding, training and staff is still needed; such support has played a significant role in aflatoxin research in the past. Various foreign agencies have given support to the Department of Agriculture through bilateral or multilateral assistance.
The United Kingdom has provide training, equipment, staff and volunteers to join in collaborative projects with Thai researchers, at a value of approximately 15 million baht (US$600,000). The United States Agency for International Development in phase 1 of its contract, has approved a soft loan of approximately US$200,000 and a grant for research staff and overseas training and study tours for Thai scientists for 1985 and 1986. The United Nations Development Programme (UNDP) has approved funds of US$ 38,500 for 1985 and 1986. In addition, the Tropical Agricultural Research Centre (Japan) has approved a cooperative project with the Division of Plant Pathology and Microbiology of the Department of Agriculture on quality and preservation of maize by preventing aflatoxin contamination. The Tropical Agricultural Research Centre supplies senior researchers, training, analytical equipment and software.
In 1986-1991, Japanese International Cooperative Agency (JICA) agrees to finance Maize Quality Improvement Center at the Department of Agriculture a budget which comprise of 66% for aflatoxin prevention. The total budget committed was for building and sophisticated equipment at a cost of approximately 100 million baht.
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