Aflatoxins in Malaysian food

Transcription

1 Mycotoxins Vol. 50, Aflatoxins in Malaysian food Norhayati ALl Introduction Aflatoxins (AF) are carcinogenic, teratogenic and mutagenic. Naturally occurring AF are Class 1 human carcinogens, particularly the AFB1, AFG1 and AFM1 in association with human liver cancer". Contamination of AF in food is most serious in tropical and subtropical countries such as Malaysia, with the average temperature of 28 Ž to 31 Ž and heavy rainfall almost throughout the year. Relative humidity is in the range of 70% to 80% during wet season and 50% to 60% during dry season. Under these conditions, commodities are easily deteriorated and very susceptible to fungal growth and mycotoxins production. Contamination could take place at any points in the food chain from cultivation through harvesting, storage, distribution, processing and consumption. As far as contamination of mycotoxins is concerned in Malaysia, research and monitoring work focus only on AF. Overall, there are still insufficient reports on the occurrence of AF in locally available food (and almost no report on the occurrence of other mycotoxins), to give a representative scenario of the problem in this country. The economy of Malaysia Malaysia is now a manufacturing-based economy and also an importing country where 54. 2% of the total supply of goods and services are imported. For the domestic supply, only 6.0% are from agricultural sector whereas 15.8% are from manufacturing sector. The important agricultural products are palm and palm kernel oil, rubber, paddy, fisheries, livestock, fruits, cocoa, pineapple, green tobacco leaves and pepper. Major exports are electrical and electronic products (50.8%), manufactured goods (28.8%), crude petroleum and LNG (5.3%), crude and processed palm and palm kernel oil (5.2%), timber (2.2%), rubber (0.3%), tin (0.3%) and other commodities including pepper and cocoa (5.2%). Food such as wheat, dairy products and raw beat and cane sugar are imported from Australia, USA, Denmark, Fiji, Saudi Arabia, and China. Additional supply of rice is imported from Thailand and Vietnam, and peanut from Thailand, India and Indonesia. Raw corn, tapioca and soybean are also imported for use as feedstuffs. The institutional strength AF research in Malaysia started at the Institute of Medical Research (IMR) in 1965 with a survey on the AF contents in various foods. The research was taken over by the Malaysian Agricultural Research and Development Institute (MARDI) in 1981 and in 1982 the regulatory limit of AF in Malaysia was formulated. In 1983, the Department of Chemistry Malaysia (DOC) Department of Chemistry Malaysia, Jalan Tu11,10450 Penang, Malaysia

2 32 Mycotoxins under the Ministry of Science, Technology and Environment was designated to monitor the presence of AF in Malaysian food for the regulatory control. Recently, this work is shared with the Food Quality Control (FQC) labs under the Ministry of Health. Out of 9 DOC and 9 FQC labs throughout Malaysia, only 6 DOC and 2 FQC labs currently carrying out the analytical work for AF. The chemical assays since 1965 have been various methods of extraction with the detection by TLC or HPLC. These include the Tropical Products Institute (TPI) and modified methods, mini column, AOAC-CB standard and modified methods, ELISA, DOC in-house method, FDA monoclonal affinity column, Aflatest-p affinity column and multifunctional SPE column cleanup. Research work on mycotoxins at MARDI and local universities may also include a biological detoxification projects, studies on the growth and aflatoxigenicity of fungi in culture, regional culture collections, and mycological and plant pathological studies on some of Aspergillus, Fusarium and Penicillium species. The occurrence of AF in Malaysian food Tables 1 and 2 show the natural occurrence of AF in Malaysian food compiled from the reports of IMR, MARDI, DOC and FQC labs'. Improvement on the sensitivity of the analytical methods improved the results obtained through the years studied. occurrence For the monitoring work, the of AF in food found to be very low where a number of labs reported negative results in all of the samples analyzed. Most of the samples submitted to the labs are commercial and imported food taken at retail outlets and points of entry. The regulatory monitoring reports must always consider the problem of a non-homogeneous distribution of AF in the samples submitted since a proper sampling procedure and a national official method for the analysis of AF Table 1 Natural Occurrence of AF in Malaysian Food by Year Studied. a raw peanut kernel only b AFM, ranged pg/kg c May include wheat & products, corn & products, other crude & edible oils, beans, dhall & other nuts, dates, chocolate, canned meat, canned mushroom, "ikan bilis", "Tim-Cheong", "belacan/cincalok", etc.

3 Vol. 50, Table 2 Natural Occurrence of AF in Malaysian Food by Regulatory Monitoring Work a Classification on types of food may not be standardized among labs b Data from these labs were chosen : DOC labs located in P. Jaya ('98-6/'99), Penang (8/'98-6/'99) and Kucing ('96-'98), and FQC lab in Selangor ('95-'96). Other labs reported negative results in almost all the samples. Table 3 Natural Occurrence of AF in Peanut Candy ("kacang tumbuk"). a Author's data5~ have not yet been stated in Malaysia. Collaborative study on the analytical methodology and coordination of the information and data obtained among institutions, laboratories and ministries involved have yet to be familiarized. The overall data showed AF contamination at variable levels in peanut and products, chilly and products, spices, pepper, cocoa beans, copra, rice, fresh cow milk, eggs and chicken liver. Contamination of AF in imported food is at low occurrences. Raw peanut kernel and products always found to be contaminated with high levels of AF. Among the peanut products contaminated, peanut candy or locally known as "kacang tumbuk", made of finely ground peanut and sugar, is prone to contain toxic levels5' (Table 3). Rice is a staple food of Malaysians. Stored paddy, rice and rice flour were found to be free or contaminated with a very low level of AF. Chilly, chilly products and spices, in dry or wet forms, are the important ingredients in typical Malaysian food and found to be contaminated with AF mainly due to the storage problem along the food

4 34 Mycotoxins chain. Pepper and cocoa beans are the export commodities and found to be contaminated with AF due to the traditional drying and storage procedures. However, pepper intended for export has been reprocessed including recleaning. It was noted that the contaminated pepper, cocoa beans, and raw peanut kernel, with higher levels of AF were having moisture contents (MC) higher than the recommended level. Other commodity such as copra was also contaminated due to the traditional drying and storage procedures. Only one study was reported for AFM1 where fresh milk, eggs and liver were contaminated respectively. at levels of 0.24, and pg/kg, Current research and existing preventive measures MARDI is currently carrying out a major project to monitor the AF contamination in raw peanut kernel, and studies on the effect of heat to the naturally contaminated kernel during roasting and other food production processes. MARDI is also currently involved with the other 15 countries to evaluate a robust, simple and cost-effective analytical method for the analysis of AFB1, AFM1 and fumonisins in food and feed applicable in the developing countries. The DOC and FQC labs are now updating the competency of the analysts and the reliability of the analytical methods to a certain QA system, whereby SOP and validation of methods used must be prepared for assessment. For existing preventive measures, there is a certain standard with regard to fungal growth for cocoa beans and palm kernel. A general accepted rule for storage of cereals such as paddy and rice is to keep the MC of about 13% with environmental relative humidity below 60%, and for commodities with high contents of fat and oil, such as peanut, cocoa beans and copra, the MC should be less than 8%. For regulatory control, Food Regulations 1985 through the Malaysia Food Act 1983 mentioned the maximum permitted level of mycological contaminant (AF or any other mycotoxin) is 35 ppb in all food. Conclusion There is an urgent need for a more extensive, systematic and reliable analytical work to study the contamination of mycotoxins, particularly AF, in Malaysian food to accurately understand and evaluate the extent of the problem. Efforts should be made to identify the stage of contamination in the food chain, as to tackle the problem effectively. The regulatory control is ultimately based on the ability of analysts to accurately identify and quantify the toxins, thus, expertise in the analytical methodology and the number of fungal and mycotoxin researchers in this country should be increased. Farmers, traders, consumers and as well as policy makers should be made aware of the adverse health, animal production and economic implications of mycotoxins. Epidemiological studies to estimate the AF intake by a population and the incidence of chronic diseases such as primary liver cancer in Malaysia should be established. References 1) IARC : "Monograph on the Evaluation of Carcinogenic Risks to Humans", Vol. 56, p (1993), IARC, Lyon. 2) Ministry of Finance Malaysia, K. L.: "Economic Report 1995/96" p (1995).

5 Vol. 50, ) Beardall, J.: "Report on ASEAN Fungal and Mycotoxin Research Activities" p (1993), Carleton University, Ottawa. 4) Mat Isa, A., Abidin, H.: "Overview on the status of aflatoxin contamination in selected Malaysian agricultural commodites,l7th ASEAN Technical Seminar on Grain Postharvest Technology" p.1-7 (1995) Lumut, Malaysia. 5) Ali, N., Hashim, N., Yoshizawa, T.: Food Addit. and Contam.,16, (1999). Dept. of Chemistry Malaysia, Jalan Tull, Penang, Malaysia.