aflatoxin: Introduction to dried figs

aflatoxin :Introduction to dried figs

1. The elaboration and acceptance of a Code of Practice for dried figs by Codex will provide uniform guidance for all countries to consider in attempting to control and manage contamination by various mycotoxins, specifically aflatoxins. It is of high importance in order to ensure protection from aflatoxin contamination in both producer and importer countries. All dried figs should be prepared and handled in accordance with the Recommended International Code of Practice – General Principles of Food Hygiene1 and Recommended International Code of Hygienic Practice for Dried Fruits2 which are relevant for all foods being prepared for human consumption and specifically for dried fruits. It is important for producers to realize that Good Agricultural Practices (GAP) represent the primary line of defence against contamination of dried figs with aflatoxins, followed by the implementation of Good Manufacturing Practices (GMP) and Good Storage Practices (GSP) during the handling, processing, storage and distribution of dried figs for human consumption. Only by effective control at all stages of production and processing, from the ripening on the tree through harvest, drying, processing, packaging, storage, transportation and distribution can the safety and quality of the final product be ensured. However, the complete prevention of mycotoxin contamination in commodities, including dried figs, has been very difficult to achieve.


2. This Code of Practice applies to dried figs (Ficus carica L.) of commercial and international concern, intended for human consumption. It contains general principles for the reduction of aflatoxins in dried figs that should be sanctioned by national authorities. National authorities should educate producers, transporters, storage keepers and other operators of the production chain regarding the practical measures and environmental factors that promote infection and growth of fungi in dried figs resulting in the production of aflatoxin in orchards. Emphasis should be placed on the fact that the planting, pre-harvest, harvest and post-harvest strategies for a particular fig crop depends on the climatic conditions of a particular year, local production, harvesting and processing practices followed in a particular country or region.
3. National authorities should support research on methods and techniques to prevent fungal contamination in the orchard and during the harvesting, processing and storage of dried figs. An important part of this is the understanding of the ecology of Aspergillus species in connection with dried figs.

4. Mycotoxins, in particular aflatoxins are secondary metabolites produced by filamentous fungus found in soil, air and all plant parts and can be toxic to human and animals through consumption of contaminated food and feed entering into food chain. There are a number of different types of aflatoxin, particularly aflatoxin B1 have been showed toxigenic effects i.e. it can cause cancer by reacting with genetic material. Aflatoxins are produced by mould species that grow in warm, humid conditions. Aflatoxins are found mainly in commodities imported from tropical and subtropical countries with in particular peanuts (groundnuts) and other edible nuts and their products, dried fruit, spices and maize. Milk and milk products may also be contaminated with aflatoxin M1 owing to the consumption of aflatoxin contaminated feed by ruminants.

5. Aflatoxigenic fungi are spread on fig fruits during fruit growth, ripening and drying but thrive especially during the ripening and overripening phase. The formation of aflatoxins in dried figs is mainly due to contamination by Aspergillus species and particularly A. flavus and A. parasiticus. The presence and spread of such fungus in fig orchards are influenced by environmental and climatic factors, insects, (insect abundance or control in an orchard is related to the applied plant protection measures so could be included in cultural practices but to point out its significance can be left as another factor), cultural practices, floor management and susceptibility of fig varieties.

6. The aflatoxin-producing Aspergillus species and consequently dietary aflatoxin, contamination is ubiquitous in areas of the world with hot humid climates. A. flavus/A. parasiticus cannot grow or produce aflatoxins at water activities less than 0.7; relative humidity below 70% and temperatures below 10 ºC. Under stress conditions such as drought or insect infestation, aflatoxin contamination is likely to be high. Improper storage conditions can also lead to aflatoxin contamination after crops have been harvested. Usually, hot humid conditions favour mould growth on the stored food which can lead to high levels of aflatoxins.

7. Application of the following preventive measures is recommended in dried fig producing regions in order to reduce aflatoxin contamination by application of good practices: a) Information on contamination risk. Ensure that regional/national authorities and grower organisations:

– Sample dried figs representatively for analysis to determine the level and frequency of aflatoxin contamination; sampling should reflect differences in areas, time of the year and stage from production to consumption. – Combine this information with regional risk factors including meteorological data, cultural practices and propose adapted risk management measures. – Communicate this information to growers and other operators along the chain. Use labelling to inform consumers and handlers on storage conditions.

b) Training of producers. Ensure training of producers with regards to: – Risk of mould and mycotoxins. – Conditions favouring aflatoxigenic fungi and period of infection. – Knowledge of preventive measures to be applied in fig orchards. – Pest control techniques.

c) Training of transporters, storage keepers and other operators of the production chain. Ensure training regarding the practical measures and environmental factors that promote infection and growth of fungi in dried figs resulting in a possible secondary production of aflatoxins at post harvest handling and processing stages. Besides these, all applications should be documented.

d) Encourage related research.

8. In developing training programs or gathering risk information, emphasis should be placed on the fact that the planting, pre-harvest, harvest and post-harvest strategies for a particular fig crop depends on the climatic conditions of a particular year, local production, harvesting and processing practices followed in a particular country or region.
9. This document is intended to provide guidance for all interested parties producing and handling dry figs for entry into international trade for human consumption. All dried figs should be prepared and handled in compliance with the Recommended International Code of Practice – General Principles of Food Hygiene and Recommended International Code of Hygienic Practice for Dried Fruits, which are relevant for all foods being prepared for human consumption. This code of practice indicates the measures that should be implemented by all persons that have the responsibility for assuring that food is safe and suitable for human consumption.

10. Fig differs from other fruits, which has potential risk of aflatoxin contamination, with its fruit formation and properties. Its increased sensitivity is due to juicy and pulpy skin, and the cavity inside the fruit and the suitable composition rich in sugar. Thus, toxigenic fungi may grow and form aflatoxins on the outer surface or inside the cavity even if no damage occurs on the skin. The critical periods for aflatoxin formation in dried fig fruits starts with the ripening of figs on the tree, continues during the over-ripe period when they lose water, shrivel and fall down onto the ground and until they are fully dried on drying trays. Fungal growth and toxin formation can occur on the outer fleshy skin and/or inside the fruit cavity. Some insect pests as the Dried Fruit Beetle (Carpophilus spp.) or Vinegar flies (Drosophila spp.) that are active at fruit ripening stage may act as vectors in transferring the aflatoxigenic fungi to the fruit cavity.

11. The main requirement is to obtain a healthy plant and good quality product by applying necessary agricultural techniques for prevention/reduction of aflatoxin formation.
12. Fig, Ficus carica L., as a dioecious tree has male and female forms that bear two to three cycles of fruits per year.

13. Caprification is a process applied in case female fig fruits of a certain variety require pollination for fruit set. The “profichi” (ilek) fruits of male figs possessing fig wasps (Blastophaga psenes L.) and pollen grains are either hung or placed on female fig trees to pollinate and fertilize the main and second crop (iyilop) fruits. The pollen shedding period of the male flowers in male fig fruits should coincide with the ripening of the female flowers in female fig fruits.

14. Ostiole or eye is the opening at the distant end of the fruit that may, if open, provide entrance to the vectors, Dried Fruit Beetle (Carpophilus spp.) or Vinegar flies (Drosophila spp.) for dissemination of aflatoxigenic fungi.
3.1 Site selection and orchard establishment (planting) 15. Fig trees grow in subtropical and mild temperate climates and have a short dormancy period which restricts fig growing in low temperatures in winter rather than high temperatures in summer. Low temperatures right after bud-break in the
spring and during October – November before shoots are hardened, can damage the tree. Freezing temperatures in winter may affect the fig wasps over-wintering in male fruits and may create problems in fruit set.

16. High temperatures and arid conditions in spring and summer can increase sunscald, result in early leaf fall if severe, cause substantial problems in quality and trigger aflatoxin formation.

17. The fig varieties may vary regarding their tendency for cracking/splitting however high relative humidity and rainfall during the ripening and drying period must be taken into account before establishing the orchard. High humidity and rainfall can increase ostiole-end cracking, development of fungi and decrease of quality.

18. Fig trees can be grown in a wide range of soils such as sandy, clayey or loamy. A soil depth of at least 1-2 m accelerates the growing of fig trees which have fibrous and shallow roots. The optimum pH range for soil is 6.0 – 7.8. The chemical (such as pH) and physical properties of the orchard soil can influence the intake of plant nutrients and consequently dried fig quality and resistance to stress conditions, thus soil properties must be fully evaluated before orchard establishment.

19. The level of the underground water table must not be limiting. Availability of irrigation water is an asset to overcome drought stress.

20. The orchards should be established with healthy nursery trees that are free from any insects and diseases. Adequate space, which is generally 8 m to 10 m, should be given between the rows and the trees to allow the use of necessary machinery and equipments. Before planting the way the fruits will be utilized (fresh, dried or both) need to be considered. Other species present in the orchard should also be considered. Species which are susceptible to aflatoxin formation such as maize should not be produced around the fig orchards. Materials remaining from the previous crops and foreign materials should be cleaned and if it is needed the field can be fallowed in the following few years.

3.2 Orchard management 21. Practices such as caprification, pruning, tillage, fertilization, irrigation, and plant protection should be applied on time and with a preventive approach in the framework of “Good Agricultural Practice”.

22. Cultivation practices, both in the orchard and in the vicinity, that might disperse A. flavus/A. parasiticus, and other fungal spores in the soil to aerial parts of trees should be avoided. Soil as well as fruits and other plant parts in fig orchards can be

rich in toxigenic fungi Soil tillage practices must be terminated one month before the harvest. During the growing seasons, roadways near the orchards should be watered or oiled periodically to minimise outbreaks of mites as a result of dusty conditions. The devices and equipments should not damage fig trees or cause cross contamination with pests and/or diseases.

23. Fig trees must be pruned lightly and all the branches and other plant parts must be removed from the orchard in order to avoid further contamination. Direct incorporation of all parts into the soil must be avoided. After soil and leaves analysis, based on the expert proposal proper composting can be recommended prior to incorporation of the organic matter.

24. Fertilization affects the composition of fruit and stress conditions may trigger toxin formation. Also excess nitrogen is known to enhance fruit moisture content which may extend the drying period. Fertilizer applications must be based on soil and plant analysis and all recommendations must be made by an authorized body.

25. An integrated pest management programme must be applied and fruits or vegetables that promote infestation with dried fruit beetles or vinegar flies should be removed from the fig orchards since these pests act as vectors for the transmission of fungi especially into the fruit cavity. Pesticides approved for use on figs, including insecticides, fungicides, herbicides, acaricides and nematocides should be used to minimise damage that might be caused by insects, fungal infections, and other pests in the orchard and adjacent areas. Accurate records of all pesticide applications should be maintained.

26. Irrigation should be implemented in regions or during periods with high temperatures and/or inadequate rainfall during the growing season to minimise tree stress, however, irrigation water should be prevented from contacting the figs and foliage.

27. Water used for irrigation and other purposes (e.g. preparation of pesticide sprays) should be of suitable quality, according to the legislation of each country and/or country of import, for the intended use.

3.3 Caprificarion 28. Caprifigs (male fig fruits) are important for fig varieties, which require for fruit set. Caprifigs should be healthy, free from fungi and should have plenty and live pollen grains and wasps (Blastophaga psenes L.). During pollination of female fig fruits by fig wasps, which pass their life cycle in caprifig fruits, Fusarium, Aspergillus spp. and other fungi can be transported to the female fig fruits from the male fruits

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