Reducing aflatoxin in peanuts using agronomic management and bio-control strategies in Indonesia and Australia

CP/1997/017: Reducing aflatoxin in peanuts using agronomic management and bio-control strategies in Indonesia and Australia

Indonesia

Queensland Department of Primary Industries and Fisheries, Australia

Dr Graeme Wright
Phone: 07 41600734
Fax: 07 41623238
Email: graeme.wright@dpi.qld.gov.au

• Research Institute for Legumes and Tuber Crops, Indonesia
• Assessment Institute for Agricultural Technology, Indonesia
• Gadjah Mada University, Indonesia
• University of Sydney, Australia
• SEAMEO Regional Centre for Tropical Biology, Indonesia

$953,736

01/07/2001 - 30/06/2004

01/07/2004 - 31/12/2006

Dr T K Lim

While there has been an enormous amount of research on the incidence and management of aflatoxin in peanuts, the adoption of new technologies in both developing and developed countries has been slow. Aflatoxin is a carcinogen, immune-suppressing and anti-nutritional natural contaminant of peanuts and hence is a major human food and animal feed quality problem throughout the world. The world wide increase in the incidence of hepatitis B and C virus (now up to 25% in some countries) is also increasing the importance of AF as a health risk since the toxin is estimated to be 25 times more potent in people with these liver diseases than in uninfected people. In countries with developed food systems the consequences of AF are largely economic, affecting the price received for peanuts by farmers, but in developing countries the price is mostly paid in the health of the population, since contamination by the toxin is commonly ignored. Current levels of aflatoxin in foods at Indonesian markets have the potential to cause more than 20,000 deaths per year.

In Australia, where aflatoxin-positive kernels are removed from contaminated loads by the peanut shelling industry, the reduction of aflatoxin in peanuts has recently become a major issue for peanut growers because the shelling industry has started to charge a penalty for loads of peanuts with unacceptable aflatoxin levels (whereas previously these costs were absorbed by the industry).

The aim of this project was to minimise aflatoxin contamination in Indonesian and Australian peanuts through the research, development and extension of appropriate on-farm and postharvest management practices. It also aimed to foster the implementation of aflatoxin control strategies in Indonesia by providing a simple, rapid and low-cost analytical system for aflatoxins.

In Indonesia, the research team surveyed peanuts for incidence of A. flavus and aflatoxin at various stages in the food delivery chain (farm-buyer-retailer) to assess critical hazard points for aflatoxin contamination.
The team then developed and implemented land and crop management systems to minimise contamination in the field and during postharvest production for both Indonesian and Australian cropping systems. They also assessed peanut varieties that matured early in the season and thus avoided the late-season drought conditions. Further field-based research and extension identified and tested competitive non-toxic A. flavus and A. parasiticus strains, compared them to existing strains in the laboratory, and conducted large field experiments to determine the optimum strategy for bio-control of the fungus.
The project also included lab experiments and scenario analyses to determine the influence of the environment and substrate upon aflatoxin production. The results were used to develop monitoring tools and a decision-support package.
The Australian research team trained Indonesian scientists in crop modelling, aflatoxin scenario analysis, bio-control technology and aflatoxin monitoring, and developed simple protocols for sample preparation. Indonesian personnel worked with the researchers to develop strategies for the introduction of aflatoxin monitoring and control in Indonesia.

The team surveyed Indonesian peanuts for incidence of A. flavus and aflatoxin at various stages in the food. The project demonstrated that a significant and even alarming aflatoxin problem exists within the peanut food chain in Indonesia. While aflatoxin contamination in the food chain was relatively minor at the farmer/trader level in peanut production systems in Java, there were significant levels of aflatoxin contamination found in peanuts and peanut products at the retail level (e.g. raw peanuts and peanut sauces etc.), thus indicating that aflatoxin-affected peanuts were entering the food chain via postharvest contamination. A related survey of imported peanut products also suggested that, in general, aflatoxin contents in raw peanuts were low at the point of importation, but increased dramatically at the retail level.

The survey also highlighted that the aflatoxin problem in Indonesia has a major socio-economic impact, whereby the highly aflatoxin-contaminated peanuts are sorted out and sold at lower price to the poorer sectors of the community. As well, poorer grade (i.e. visually fungal-affected) peanuts tend to be added to peanut sauces (e.g. sambel pecel, gado gado, satee sauce etc.) which can result in alarmingly high aflatoxin concentrations in these retail products.

In Indonesia, experiments investigating the effect of harvesting time and differing seed storage treatments on kernel aflatoxin contamination in general showed only low levels of pre- and post harvest aflatoxin, and little evidence of dramatic aflatoxin build up in postharvest storage. Overall the results showed that the level of pre-harvest aflatoxin in peanuts grown in farmers' fields, and their subsequent on-farm storage, was generally low. The significant finding however was that although aflatoxin levels were generally low on-farm, the A. flavus fungus was nearly always present in most kernels (and especially in shrivelled and damaged kernels), which must therefore pose a significant risk for aflatoxin production further along in the peanut food chain (i.e. at the wholesaler and retail level where poor storage conditions often prevail).

In Australia, a web-based aflatoxin decision-support system named 'AFLOMAN' (http://www.apsim.info/apsim/afloman) was developed to allow growers to access information on when is the optimum time to harvest crops to avoid aflatoxin risk and maximise yield and quality. This package has successfully integrated most of the basic science on environmental and crop factors controlling aflatoxin production in peanuts, which was developed during the project. In high aflatoxin risk years, where end-of-season drought and high soil temperatures persist, it is important that the crop is pulled early so that pods do not enter critical kernel moisture zone of 15-30%, where aflatoxin production commences. In low risk years, where soil water content is high and soil temperatures are low, the crop should be allowed to reach full maturity to maximise pod yield and grade out.

The aflatoxin module was successfully incorporated into the APSIM peanut model, and assessed under Indonesian conditions. A newly developed software tool called 'Peanut Whopper Cropper', which allows users (i.e. researchers, industry personnel, policy makers etc.) to assess aflatoxin risk throughout Indonesian locations, was tested and validated under Indonesian conditions, and training on its use provided to Indonesian collaborators. More detailed studies in the extension project showed that environmental conditions (temperature and humidity) experienced in wholesalers, wet markets and supermarkets were highly conducive to kernel re-hydration and hence for the growth of the A. flavus fungus. As the peanut food-chain survey clearly showed very high levels of fungus in the majority of kernels (up to 60%) at all levels of food chain, there is clearly high potential for aflatoxin production in storage.

The bio-control approach as a means of minimising aflatoxins in peanuts was evaluated in Australia in a number of locations, in collaboration with a GRDC project led by Dr John Pitt from CSIRO Food Science Australia. The results indicated that although control is possible, the results are not reliable since failures to modify the proportions of toxin-forming colonies had occurred in approximately half the tests (failures were mainly associated with the environmental conditions at the time of application). The costs of treatments and the risks of failure indicated to the peanut industry (and particularly PCA) that this may not be a viable management option since the other 'best practices' can provide economic and adequate control of the problem.

ELISA aflatoxin analysis facilities were successfully developed and installed in three Indonesian centres in West, Central and East Java, and have provided a low-cost, accurate method for aflatoxin analysis in Indonesian peanut products. This technology therefore provides the Indonesian community with readily available tools to effectively analyse and hence monitor aflatoxins in the Indonesian food chain.

Results from socio-economic surveys clearly indicated there were currently few practical incentives for the Indonesian peanut industry to address the issue of aflatoxin contamination. It appears that major processors may have the greatest capacity to handle and process product in a safe manner, by possessing the greatest potential to influence product pricing and intake specifications via the 'tebasan' system or via purchases they make of intermediaries in other regionally important production areas. At a local level, logistical considerations will constrain any farmer-oriented education process due to shear numbers, lack of literacy and a poor understanding about the relatively complex processes involved in minimising aflatoxin in such a simple production system as currently exists.

Factors that may support overall supply chain upgrading include: judicious implementation of new food safety policies; public food safety education; and development of existing social capital to foster a whole-chain outlook, perhaps through community-based industry groups.