Mycotoxins in foodgrains in some Asian countries

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JOINT FAO/WHO/UNEP SECOND INTERNATIONAL CONFERENCE ON MYCOTOXINS

Bangkok, Thailand, 28 September - 3 October 1987
Marianne Flach
FAO Regional Network on Grains Post-Harvest Technology and Quality Control, Bangkok

INTRODUCTION

The FAO Project "Inter-Country Cooperation in Post-Harvest Technology and Quality Control of Foodgrains", located in Bangkok, is operating since 1983. Thirteen countries in Asia are members of this Network: Bangladesh, Burma, China, India, Indonesia, Republic of Korea, Malaysia, Nepal, Pakistan, Philippines, Sri Lanka, Thailand and Vietnam.

In 1986 a questionnaire on Grain Quality Control was sent out to the member countries, as a part of the activities of the Network. Part of the aims of this questionnaire was to find out concerning mycotoxins:

* The current situation in the region with respect to the major grains in each country;
* The existing quality criteria for the major foodgrains in the region at post-harvest level.

The National Coordinators in each member country were asked to supply information countrywide or on provincial basis which would indicate the relative distribution and degree of contamination in each country. With the collected information recommendations were made in order to avoid duplication of work and make full use of already to existing information.

This paper will give an overview on the work that was done in Asian countries concerning mycotoxins. It appears that since the First International

Mycotoxin Conference, 10 years ago, a lot of work has been undertaken. However, it focusses in all countries on aflatoxin. Furthermore, it should be stressed here that the gathered information is not complete:

* Information is only given for the Network member countries and not for the whole of Asia;
* Information is only given for foodgrains;
* There may be more information on research going on in the member countries, which we are not aware of, especially when reports are written in the local language.

Nevertheless, the available information is quite substantial, and it is possible to draw general conclusions and make recommendations.

AFLATOXIN IN FOODGRAINS IN SOME ASIAN COUNTRIES

Introduction

In Table 1. an overview is given of results of research and monitoring programmes in the different countries. Laboratory trials are not included, since the questionnaire focussed on the current situation concerning mycotoxins. Data are available for 11 of the 13 member countries, Burma and Vietnam do not have reports available.

TABLE 1. AFLATOXIN CONTENT OF VARIOUS GRAINS IN SOME ASIAN COUNTRIES, BASED ON FIELD STUDIES

TABLE 1. AFLATOXIN CONTENT OF VARIOUS GRAINS IN SOME ASIAN COUNTRIES, BASED ON FIELD STUDIES (continued)

TABLE 1. AFLATOXIN CONTENT OF VARIOUS GRAINS IN SOME ASIAN COUNTRIES, BASED ON FIELD STUDIES (continued)

The foodgrains most at risk are maize, peanuts and parboiled rice. Polished rice, not parboiled, seems to be relatively free from aflatoxin, but it appears that aflatoxin is concentrated in the bran layer (1). However, not much information is available on this, and none of the countries reported on it. Unrefined peanut oil as a processed product was mentioned by some countries to be contaminated with aflatoxin.

Most of the work in the region consisted of surveys to indentify the problems. Considerable work also has been put into methodologies for the detection and quantification of aflatoxin. However, sampling, sample handling and analysis is not standardised, and this makes interpretation and comparison of results difficult. Conditions in laboratories may not always be safe enough. Some countries have done studies on finding out at which stage in the post-harvest handling of foodgrains contamination is likely to occur and on how to prevent it rather than destroying the toxin. The results of those studies will be very valuable for other countries as well. A few countries have set up maximum levels for mycotoxins in grains.

In the following paragraphs country situations will be described for each commodity at risk. Based on this information recommendations will be made for future activities.

AFLATOXIN IN MAIZE IN SOME ASIAN COUNTRIES

Introduction

The top producers among the member countries are China, India, Thailand, Indonesia and the Philippines. Thailand and Burma export maize. The other countries except Pakistan are importing maize. The percentage of production retained at the farm varies. About half is retained by the farmers in Pakistan and Sri Lanka but 90% in Nepal. In Thailand however, two thirds is for export, the remainder is marketed locally, mainly for feed purpose.

China

Maize is considered to be a high risk commodity in China. The main cause is the absence of drying facilities and harvest during the rainy season. Research work has been done on aflatoxin, and also on other mycotoxins, however, at this moment there are no reports available in English.

India

In India, a study done in 1982 (3), shows that 33 out of 100 maize samples contained aflatoxin up to 321 ppb. Six out of 10 maize flour samples had aflatoxin levels upto 179 ppb.

Indonesia

The mean aflatoxin content of maize in North Sulawesi is significantly higher than in other provinces, however, the mean aflatoxin levels in other provinces is already above 100 ppb. As maize is the second staple food in certain regions of Indonesia (e.g. South Sulawesi, where per capita consumption per day can be 300-500 g), these levels give rise to considerable concern.

Another study (7) compares aflatoxin content in maize samples in East Java, North and South Sulawesi and relates it to drying and storage practices. It was found that in both North and South Sulawesi levels were higher than in East Java. In North Sulawesi; where the levels were highest, farmers usually leave the maize intact with the plant in the field for drying, for one month, after maturity. No drying is required before shelling, but fungal and insect damage occurs. In South Sulawesi farmers may store the maize for 1-2 years before selling. Although the maize is stored on the cob, the long period may enhance aflatoxin formation.

Nepal

During 1980-85 101 samples of maize and maize products were analysed for aflatoxin content. Thirty samples had aflatoxin B1 in the range of trace to 321 ppb, with 10 samples above 30 ppb (12).

In 1983-84 a study was done on aflatoxin content of maize samples from different periods after harvest (13). The data show that:

* Aflatoxin content at harvest is low;
* Aflatoxin content after some period of storage is lower in maize cobs than in shelled maize, and highest in maize flour;
* The contamination problem is more serious in the Terai area, which has a warm, humid climate.

One of the main problems causing mould growth is the fact that most of the maize, especially in the Terai area, is harvested during the rainy season and farmers do not have drying facilities. Table 3. shows some data. Farmers usually store for up to 1 year, as maize is an important staple food in Nepal. About 90% may be retained at the farm, there is little marketable surplus. The three different storage types, namely outside on an elevated structure covered by straw, hanging under the eaves of the house, and inside the house in baskets, have not been studied in relation to aflatoxin, but it may be worthwhile to find out which type is more prone to aflatoxin formation and how it can be improved.

Pakistan

During 1980-85 a study was done, during which samples were collected, from local markets, government stores etc. Maize and maize products mainly came from Lahore. Fifty-three samples were analysed, 14 (26%) contained aflatoxin in the range of 133-800 ppb (14)

Philippines

A study was done in 1982 to determine the effects of different drying methods on aflatoxin contamination of maize (22). The drying methods compared were mechanical drying, sun drying and crib drying. Both white and yellow maize were analysed. The 20 ppb level was reached in the white variety after 40, 35 and 15 days from harvest for the above mentioned methods respectively. For the yellow variety this level was attained after 35, 15 and 10 days.

The level of aflatoxin in maize differs for the various regions is the Philippines. This is apparently due to marketing, climatological and agricultural factors. For instance, one of the major maize producing areas, Cagayan Valley, consumes only maize that it produces and mills, and sends the surplus directly overland to other areas. The market flow is simple and involves few middemen. Moreover, harvesting is during the dry season. Average aflatoxin levels are in the range of 1221 ppb A second major maize producing area is South Western Mindanao. Here the maize is harvested during the wet season. Millers throughout Mindanao cannot cope with the maize supply and, therefore, part of the maize is shipped to Cebu for milling. Thereafter, the milled maize will be reshipped to Mindanao or onwards to other islands. This market flow involves several middlemen and delays. However, average aflatoxin levels are not yet alarmingly high, although above acceptable level, namely 60 ppb (16).

A study at on-farm level of maize handling states that shelled maize should be dried immediately to a safe level in order to keep aflatoxin content within safe levels. If immediate drying is not possible, than grains should be stored in unshelled form with husk, with adequate aeration for not longer than a week. At offfarm level, e.g. at trader level, it appeared that maize may be heavily contaminated already at the moment of arrival (23).

Thailand

Several studies have been done concerning aflatoxin in maize. In general it can be said that in Thailand, as in other countries in Asia, aflatoxin at harvest level is low. Two months storage at farm level does not necessarily result in high aflatoxin level, one study shows that after two months the aflatoxin content was 21 ppb. However, much depends on climatic conditions during harvesting, most of the maize is harvested during the rainy season. Also the conditions of the store are important. At silo and middlemen level aflatoxin content is often around 100 ppb (19, 20).

An interesting project is being undertaken in Thailand to combat the problem of aflatoxin in maize, a bilateral project with the UK. Results revealed the following during Phase l:

* Aflatoxin contamination at harvest is low, but increases significantly during storage;
* Mechanical drying is capable of "freezing" aflatoxin levels provided that the drying period does not exceed 48 hours;
* Both mechanically and sundried maize can be stored for at least 2 months without any increase in aflatoxin.

During Phase II low aflatoxin maize was successful produced in the rainy season by mechanically drying freshly harvested maize, which was field-dried 1-4 weeks prior to harvest. Another test during Phase II showed that one-stage drying is able to produce low aflatoxin maize, whereas two-stage drying is too slow. Farmers prefer to sell their maize as quick as possible after harvest, however, marketing problems may force them to store the maize although they might not have good storage facilities. Therefore, like in the Philippines, maize arriving at the primary merchant may have a high aflatoxin level already. Another problem is that with the existing pricing mechanism in Thailand there is no incentive for farmers and primary merchants to dry their maize below 18% m.c.

At present the project is in the third phase. Emphasis is now on producing low aflatoxin maize by giving premiums. Steps are undertaken together with the private sector (feedmillers) to include aflatoxin content in the price determination (24, 25).

AFLATOXIN IN PEANUTS IN SOME ASIAN COUNTRIES

Introduction

The main producers of peanuts or groundnuts are: India, China, Indonesia, Burma and Thailand. Peanuts are mainly used locally as food, either fresh or processed (edible oil, flour, peanut butter, crackers, candies etc.). Little is used in the member countries for feed. The quantity retained at the farm is more than 90% in Indonesia and Korea, in other countries not more than 35%.

China

Both peanuts and peanut oil (unrefined) may contain high levels of aflatoxin. The major cause seems to be rain during harvest and no drying facilities. This is especially so in the southern part of China. Contamination also occurs in a later stage, during storage. No exact data are available since there are no reports in English.

India

One study reveals that out of 124 shelled peanut samples 19 (15%) were found to have aflatoxin upto 120 ppb (3). More studies have been done but data are not available at present.

II.3.4 Indonesia

Peanuts are considered to be a high risk commodity in Indonesia. It was found (5) that contamination of peanuts usually happens at the retailer stage, and it is explained by the fact that retailers keep the nuts in uncovered containers, and they may keep the nuts for quite some time. The survey was conducted during the dry season, and levels of aflatoxin B1 at retailer stage varied from 7-2000 ppb, while at distributor stage the level was 7 ppb.

The effect of home storage on aflatoxin in peanuts has also been studied (5) and it appeared that the first traces of aflatoxin were detected only after 10 weeks of storage, but thereafter the level increased rapidly to 912 ppb aflatoxin B1 and 740 ppb aflatoxin G1 in the 28th week. However, nothing was mentioned about the way the peanuts were stored.

Another study (26) reports varying levels of aflatoxin content in peanut samples, see Table 4. Fresh and dried, unshelled peanuts contain no aflatoxin, salted peanuts had low levels and press-cake and shelled peanuts may have alarmingly high levels.

Malaysia

Several monitoring programmes on aflatoxin have been carried out between 1976 and 1984. Peanuts with shell show no or low levels of aflatoxin, shelled peanuts may sometimes have high aflatoxin levels, and among peanut products also high levels may be found, e.g. peanut butter (locally made contains more than imported), peanut candy, peanut cake and peanut gravy.

A wide variety of Malaysian dishes uses peanut as one of the ingredients and further research should be emphasized in order to trace at what stage contamination occurs and how to prevent it (11).

Pakistan

A survey was done on aflatoxin in food and feed stuffs in Pakistan during 1981-85 (14). Samples of different commodities were collected from local markets, government stores etc. Samples came from different areas of Pakistan. Forty-two samples of peanuts were analysed, and 10 contained aflatoxin B1 and B2, in the range of 24-80 ppb.

Thailand

Peanuts are widely used in Thailand, as food snacks, feed and in the production of vegetable oil. A survey was done in 1982 to study the incidence of aflatoxin in peanuts. At harvest time the aflatoxin content is still low, but shelled peanuts have a rapidly increasing aflatoxin level. Some unshelled samples however could also have an aflatoxin level of 75 ppb, even one week old samples. All peanuts were collected from middlemen stores. Peanuts are at present harvested during the rainy season and no artificial dryers are available with farmers or middlemen (21).

AFLATOXIN IN PARBOILED RICE IN SOME ASIAN COUNTRIES

Introduction

Milled rice usually contains no or very low levels of aflatoxin. However, several countries (Bangladesh, India, Sri Lanka) make note of sometimes high aflatoxin levels in parboiled rice. It is mainly the Indian subcontinent where parboiled rice is consumed, and Thailand exports parboiled rice. Only one survey in Sri Lanka, tries to relate the process of parboiling to aflatoxin formation and is therefore mentioned here.

Sri Lanka

An extensive survey (17) was done on the occurrence of aflatoxin in parboiled rice and raw processed rice in the major rice producing areas of Sri Lanka. A total of 485 samples were analysed for aflatoxin B1 and G1. Results are shown in Tables.

Table 5. Mean aflatoxin content of raw and parboiled rice in Sri Lanka, 1984

The high level of aflatoxin G1 in raw rice in Anaradhapura cannot be explained here. All parboiled rice samples show high levels of aflatoxin. It was stated in the report that commercial parboiling resulted in higher levels of aflatoxin than household parboiling. Household parboiled rice is cleaner and odourless since the process is under careful control. Commercial parboiling, however, means sometimes soaking in cold water for 2 to 4 days before steaming, and it seems that the water is very often being reused, resulting in mouldy paddy with a strong fermented odour.

II.5. QUALITY CRITERIA FOR MYCOTOXINS IN GRAINS

China, India, Malaysia, Philippines and Thailand have established national maximum levels for aflatoxin:

CONCLUSIONS AND RECOMMENDATIONS

Conclusions

1. Research and monitoring programmes focus in all countries on aflatoxin.
2. Commodities most at risk concerning aflatoxin contamination are maize, peanuts, and parboiled rice, and levels found are often high.
3. Considerable work has been put into methodologies for the detection and quantification of aflatoxin, however, sampling, sample handling and analysis is not standardised. Care should be taken in interpretation and comparison of results.
4. Some countries have done studies on finding out at which stage in the post-harvest handling of foodgrains contamination is likely to occur and how to prevent it rather than destroying the toxin. For instance, it can be concluded that:

* In many countries maize and peanuts are harvested in the rainy season, and no drying facilities are available.
* In Nepal most contamination occurs during on-farm storage, and susceptibility to aflatoxin formation is highest in maize flour, followed by shelled grains and lowest in cobs with husk.
* In Thailand maize is usually for export, and farmers only keep maize at the farm while awaiting better prices. Most farmers, however, sell quickly, and prevention of aflatoxin formation could be achieved by: quick mechanised drying at primary merchant level, fast marketing chain and premiums for aflatoxin free maize.
* Contamination of peanuts in Indonesia often finds place at retailer stage, since they keep the peanuts for long time in uncovered containers. However, more information is needed.
* Contamination of parboiled rice probably takes place during the soaking and drying process. However, more information is needed.

Recommendations

1. Setting up and coordinating of research and monitoring programmes on other mycotoxins.
2. Standardization of sampling, sample handling and analysis.
3. Testing of economic viability and acceptability of existing drying technologies.
4. Developing a field kit for analysis.
5. Improving of on-farm storage facilities.
6. There is a need for more coordination and streamlining of programmes in Asian countries. More use should be made of each others experiences and capabilities.

The "ASEAN Mycotoxin Expert Group on the Formulation of an ASEAN Aflatoxin Control Program" recommended the establishment of an ASEAN Mycotoxin Regional Training Centre and Reference Laboratory. Funding was requested Through the ASEAN Food Handling Bureau from the EG However, up till now the proposal was not yet approved. It may be worthwhile to consider the establishment of a Regional Training Centre not only for the ASEAN Region, but for Asia and Pacific countries as a whole.

In this respect it may be worthwhile to mention that a similar centre for pesticides: "Regional Pesticide Training Centre and Service Laboratory" for Asia and the Pacific Region was proposed for setting up in Chiang Mai in Thailand.

It may be considered to, instead of setting up separate laboratories and centres for pesticides and mycotoxins, to set up a regional centre for quality control as a whole.

Table 2. Mean and highest incidence of aflatoxin contamination of maize by province, Indonesia, 1983 (6)

Table 3. Aflatoxin content of maize samples related to product In Nepal, 1983-84

Table 4. Aflatoxin In fresh peanuts and peanut products in Indonesia, 1984

LIST OF REFERENCES

1. I lag, L.L. and B.O. Juliano, "Colonization and Aflatoxin Formation by Aspergillus spp. on Brown Rice Differing in Endosperm Properties', J. of Food Sc. and Agric. (1982) 33: 97-102.
2. Joarder, G.K., "Studies on the Incidence of Fungal Flora and Determination of Aflatoxin in Rice in Bangladesh", Paper presented at the PostProduction Workshop on Foodgrains, Dacca (1980).
3. Bhat, R.V., "Report on Aflatoxin Contamination of Agricultural Commodities in India and Nepal', National Institute of Nutrition, Hyderabad (1982).
4. Tulpule, P.G., V. Nagaraj and R.V. Bhat, "Environmental Contaminants in India", Department of Environment, GOI, New Delhi (1982).
5. Muhilal, and D. Karyadi, "Survey Aflatoxin Nuts and Grains", Proceedings of the 7th Annual Workshop on Grains Post-Harvest Technology, Kuala Lumpur (1984).
6. Sintha et. al., "Aflatoxin Survey of Corn in Indonesia", Proceedings on the 6th Annual Workshop on Grains Post-Harvest Technology, Bogor (1983).
7. Nagler et. al., "Aflatoxin Control in Indonesian Cereal Maize", Proceedings on the 7th Annual Workshop on Grains Post-Harvest Technology, Kuala Lumpur (1984).
8. Ryeom, K. et. al., "Studies on the Mycotic Disease, (2) Studies on the Aflatoxin:, Report of NIH Korea (1985), 22: 65-77.
9. Institute of Medical Research - Unpublished Data from the Division of Nutrition, Malaysia.
10. Yeo, H.S., "Mycotoxins in Malaysia", Proceedings of the Regional Workshop on Mycotoxins, Bangkok (1983).
11. Mat, l.B.A. and T.E. Siong, "The Status of Aflatoxin Research in Malysia", Report of the Technical Consultation of the ASEAN Mycotoxin Expert Group on the Fommulation of an ASEAN Aflatoxin Control Program, Kuala Lumpur (1984).
12. Karmacharya, S., "Aflatoxin Contamination in Food of Nepal", First National Seminaron Food Industry and Food Technologies, Tribuvhan University, Kathmandu (1985).
13. Karmacharya, S., "To Assess Aflatoxin Contamination in Various Maize Samples Collected from Kathmandu Valley and its Adjoining Hills and Terai Parts of Nepal", Central Food Research Laboratory, Kathmandu (1984).
14. Shah, F.H. et. al., "Mycotoxins in Food and Feed Stuffs", PCSIR, Lahore (1985).
15. Bulatao-Jayme et. al., "Dietary Aflatoxin and Hepato Cellular Carcinoma in the Philippines", Phil. J. Internal Medic. (1981): 95-101.
16. Bulatao-Jayme et. al., "Epidimiology of Primary Liver Cancer in the Philippines with Special Consideration of a Possible Aflatoxin Factor", J. Phil, Med. Assn. (1976): 129-150.
17. Bandara, lM.R.S., "Recent Studies on Aflatoxins in Rice in Sri Lanka", Proceedings of the Regional Workshop on Rice Post-Harvest Technology, Cabanatuan (1984).
18. Samarajeewa, U., "A Preliminary Survey of the Aflatoxin contamination of Some Market Foods in and around Kandy", Sri Lanka J. Agric. Sc. (1984): 128-131.
19. JICA, "The Report for the Technical Cooperation Project on Malze Development in Thailand, 19771984", Bangkok (1984).
20. Siriacha et. al., "Aflatoxin Survey of Corn in Indonesia", Proceedings of the 6th Annual Workshop on Grains Post-Harvest Technology, Bogor (1983).
21. Wong-Urai, A. et. al., "Incidence of Aflatoxin in Preand Post-Harvested Peanuts", Proceedings of the 6th Annual Workshop on Grains Post-Harvest Technology, Bogor (1983).
22. Marajas, A., "Post Production Microbial Infection and Aflatoxin Contamination in Corn", Terminal Report, World Bank Assisted Project, NAPHIRE, Manila (1983).
23. NAPHIRE, Annual Report 1985, Munoz (1986).
24. Meadley, J. et. al., "Report on Aflatoxin in Maize in Thailand, Phase I", Rural Investment Overseas Ltd. (1985).
25. Meadley, l et. al., "Report on Aflatoxin in Maize in Thailand, Phase II', Rural Investment Overseas Ltd. (1985).
26. Endang, S.M.S. et. al., "Pole Pencernaar Aflatoxin Dalam Kacang Tanah", Kongress llmiah National Ke V ISFI, Bandung (1984).

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