aflatoxin contamination ,All stages of producing peanuts

aflatoxin contamination

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All stages of producing peanuts to trade this product 9



aflatoxin contamination


Briquette and pelletization

Energy shortage in rural areas has several far-reaching ill consequences, the security of fuel wood forces people to use animal dung and crop residue as fuel, reducing the soil fertility and productivity. Following is the method for briquette and pelletization of groundnut shell for fuel purpose. The process of briquette and pelletization is based on the principle that at set pressure fraction is related logarithmically to the height of the layer of compressed material. During the pelleting of fine-ground material, fraction increased as the diameter of the cylinder decreased and as pressure increased. It was calculated that the length of the holes in roller type disc dyes and ring dyes should be increased as the diameter of the holes and particles size of the material increased. Wafers of groundnut husk and bark could be formed by pressure <11MPa. The moisture content of the material should be between 10 to 16 percent and particle density 1.0 to 1.4 g cm-3. (Esaki, et al., 1986). In India small-scale industries are forming briquette from groundnut husk, which is being used in other industries as a fuel for boilers. The briquette industries require a strong support and encouragement from the governments. Please see Figure 31.


 Figure 31: Small-scale industries preparing groundnut Briquettes for fuel purposes.


aflatoxin contamination


aflatoxin contamination

The shell is also used as soil amendment and manure, mulch, particleboard, in India and other developing countries.


2.8.5 Aflatoxin contamination 

History and origin: The aflatoxin problem was first recognized following outbreaks of Turkey “X” disease in the United Kingdom in 1960. Research revealed that the disease was caused by toxins produced by strains of the fungus Aspergillus flavus, which had grown in the groundnuts. The term aflatoxin is used to designate a group of organic metabolites, more or less toxic to animals, of certain strains of fungi belonging to the species Aspergillus flavus ands A. parasiticus. Six aflatoxins have been identified:

Aflatoxin B1 = C17 H12 O6

Aflatoxin B2 = C17 H14 O6

Aflatoxin G1 = C17 H12 O7

Aflatoxin G2 = C 17 H14 O7

Aflatoxin M1 = 4-hydroxyflatoxin B1

Aflatoxin M2 = 4-hydroxyaflatoxin B2

Detailed studies show that aflatoxin B1 is the most commonly occurring form. All the aflatoxins can be toxic at certain concentrations and may cause primarily liver cancer in animals and human. They can also cause lack of appetite, loss of weight, haemorrhage, ascites and abortion. Young animals are more sensitive and vulnerable to aflatoxicosis than older ones. There are two types of aflatoxin toxicity: direct toxicity and relative toxicity; both can be acute or chronic. This issue has become a subject for concern in agriculture on global scale. Many countries have assigned high priority to research to find a solution to aflatoxin contamination of groundnut. It is a serious problem in the warm to hot subtropical moist regions of the world and is more serious during and following alternative dry and wet periods, i.e. drought followed by showers. Fungal growth and aflatoxin production in the pods is favoured, when temperature range from 20 to 30°C and the relative humidity in the pod microenvironment ranges from 85 to 95 percent. Invasion of fungus to groundnut can occur during flower and peg formation, gradually as the pod mature and rapidly as the pod become over mature. Mature intact pods with thick sclerotize cellular components and kernels with compact seed coat (testa) are less susceptible. Seed coat is a barrier to fungal infection, as in seed with higher Ca content in seed coat decreased the growth of A. flavus. The results revealed that Ca content in seed coat is more important than Ca in pericarp (Field Crop Research, 1997 pp. 9). The presence of a “natural barrier” to invasion of undamaged pods was also considered and suggested possible antagonism and competition by Trichoderma viridi and Penicillium spp. With in the endocarp community (Garren, 1966). Preharvest contamination: Late season drought spell, particularly in the semi-arid region is a major factor associated with aflatoxin contamination. Reduced metabolic activity associated with decreased pod moisture content under drought stress seems to increase susceptibility of groundnuts to A. flavus infection. However, another possible role of drought stress in preharvest fungal infection could involve suppression of microbial competitors of aflatoxin producing fungus by elevated temperatures in the pod zone (Mehan, et al., 1991). Pod splitting is another factor contributing to aflatoxin contamination. Pod maturing under fluctuating soil moisture conditions during seasons of inadequate or irregular rainfall, are prone to pod splitting. Seed in split pods are frequently invades by A. falvus and subsequently become contaminated with aflatoxins. It is well established that A. flavus invasion can occur in soil during pod development and maturation; the fungus directly penetrates the pod wall or enters passages created by pod pests and diseases/lesions. However, the exact mode of infection of groundnut pod has not been fully elucidated. To control the invasion of A. flavus under the drought situations efforts are needed to under stand the mechanism of A. flavus invasion at different levels of pod moisture and genotype variations for the pod characteristic to develop cracks under varying soil moisture regimes.

Post-harvest contamination

During drying: In most of the groundnut-producing countries the weather remains warm, wet during the drying period and the risk of aflatoxin contamination is increased. At harvest groundnut pods contain moisture content about 45 to 55 percent and a complex of microorganisms, the endocarp microflora, which includes A. flavus also. When moist pods are lifted and cured/dried in windrows or heaps there may be considerable invasion of seed by A. flavus and other fungi already existed in the shell. This process is encouraged, if drying is slow because seed remain in very susceptible range of 12 to 30 percent moisture content for extended period. A rain shortly after lifting is not particularly harmful, but a rain after the groundnuts are partially dried, followed by poor drying is likely to result in aflatoxin contamination (Troeger, et al., 1970). Rains in the evening may keep the groundnuts wet all night, thus providing fungi with needed moisture to multiply. Rains early in the morning are less likely to slow down drying and accelerate mould growth, because of effective daytime drying. In Nigeria, in the areas where rains continue after harvest, field drying of groundnuts is serious problem of aflatoxin  contamination (McDonald and Harkness, 1965). The use of inverted windrows compared to random windrows or heap has shown to speed the curing and drying process (Pettit, et al., 1971). Groundnut pods positioned at the top of inverted windrows reside where air currents move more rapidly and the atmosphere humidity is low as compared with positions close to soil surface. Thus the pod at the top of inverted windrows has less chances of invasion by A. flavus than the pods close to soil surface.

Lower levels of A. flavus infection and aflatoxin contamination have been reported in groundnuts dried in inverted windrows than in inverted random windrows (Porter and Garren, 1970). Thus inverted windrows shorten the time required to cure groundnuts in field and help to reduce the number of kernels invaded by A. flavus and other fungi. However, to avoid infection and aflatoxin contamination because of prolonged periods of rain, groundnut should be threshed as soon as possible with final drying achieved under controlled conditions, if groundnut is cultivated in large scale. In case the drying facilities are inadequate groundnuts should be left in the inverted windrows rather than combined and held for drying. Even during periods of rain, the risk of aflatoxin contamination is probably less for groundnuts in inverted windrows than for those held in dryers without proper ventilation (Dickens, 1977). In India lot of work on the aflatoxin problem has been conducted by the ICRISAT, from other developing countries the reports are sporadic, however, more systematic studies are required to prevent the invasion of A. flavus during curing and drying.

During storage and shipment: The number of ecological studies of storage fungi involving quantitative mould count of populations is limited. In Egypt, groundnut seed were adjusted to 8.5, 13.5, 17.5 and 21 percent moisture levels and stored for 6 months at 5, 15, 28 and 45°C and A. flavus was found to be the dominant fungus followed by A.niger, A.terreus and P.funiculosum (Moubasher, et al., 1980). The main factors influencing the growth of A. flavus and other storage fungi in groundnut are moisture (relative humidity), temperature, storage period and gaseous composition of the storage atmosphere. High mycofloral counts have been associated more often with high initial moisture contents of groundnuts going into storage than with any other factor. The literature on the influence of moisture, temperature and other factors on the growth of A. flavus in groundnuts have been comprehensively reviewed by Diener and Davis (1977). A. flavus infection and aflatoxin contamination may increase in groundnuts during storage until their moisture content drops below 9 percent. Natural accumulation of carbon dioxide (CO2) and decreased levels of oxygen (O2) in closed storage reduce mycoflora development. Fungus growth and sporulation were reduced with each 20 percent increase in CO2 from 40 to 80 percent. No growth occurred in 100 percent CO2. Visible growth and free fatty acid (FFA) formation by A. flavus were inhibited at 86 percent. RH decreased by 20 percent at 17°C and 60 and 40 percent CO2 at 25°C. FFA levels decreased as RH decreased from 99 percent to 92 percent to 86 percent (Lander, et al., 1967). Low temperatures and uniform moisture distribution reduce mould growth and insect activity. Aeration is necessary to reduce aflatoxin contamination during storage. High relative humidity and temperature, rainwater leakage and insect infestation are critical factors that contribute to aflatoxin contamination of groundnuts in storage.

Groundnut meal has traditionally been an important component of poultry and other livestock feeds both in groundnut producing and importing countries. The economics of some of the developing countries are strongly dependent on export of groundnuts and groundnut products. Therefore, every effort should be made to reduce aflatoxin contamination and so maintain trade in groundnuts and groundnut products. The problem of mould damage and mycotoxin contamination can be minimized by improving facilities for storage at port and transient points and on ship. Use of airtight polyethylene bags with silica gel may reduce the proliferation of A. flavus by lowering the relative humidity of the storage microenvironment.

Need of aflatoxin contamination control in developing countries

In developing countries the problem of the aflatoxin contamination is more serious and farmers are still following the old practices of harvesting, curing, drying and storage, more over the environment during harvesting and storage remains congenial for the mould growth. Farmers need to be educated about the ill effects of the aflatoxin production and to follow a package of practices for the control of invasion by the fungus A. flavus. Therefore several National and International Organizations in the developing countries are organizing the programmes for the control of the aflatoxin in groundnuts.

In October 1987 ICRISAT organized International Workshop on Aflatoxin Contamination of Groundnut. To present overview of the work and problems of aflatoxin contamination in the developing countries, showed that in many developing countries there is only limited or no facilities for monitoring groundnut and groundnut products for aflatoxin contamination. There are also possible synergistic interaction between aflatoxin and infectious hepatitis virus B and there is evidence that the effects ingestion of aflatoxin are much more serious in the case of children suffering from severe protein malnutrition and unfortunately this is a common condition in some countries where aflatoxin occur.

African Groundnut Council (AGC) in 1975, on the basis of scientific information on A. flavus and other mycotoxin producing fungi launched an aflatoxin control programme in collaboration with EEC (European Economic Community) and UNDP (United Nations Development Programme) with technical assistance from the FAO. In Zambia, groundnut kernels meant for export are routinely monitored for aflatoxin contamination. A committee to coordinate action on the aflatoxin problem in Nigeria was constituted in 1961 with representatives from four ministries, the Institute for Agricultural Research (IAR) Zaria, The Nigerian Stored Products Research Institute (NSPRI) and Northern Nigeria Marketing Board. This committee was charged with the responsibility of assessing the extent of the aflatoxin problems in groundnut in the country and of initiating and coordinating all actions leading towards its elimination.

The IOPEA has started, in small way in India, its endeavour to educate farmers about sound post harvest practices in Gujarat, which is one of the largest groundnut-producing states in the country. In Andhra Pradesh the farmers do not seems to be as conscious as their counterparts in Gujarat about proper drying, storage and moisture levels. In both the states in UNDP sub-programme on “Promoting Groundnut as Food Crop for Sustained Nutritional Security” implemented by National Research Centre for Groundnut to educate the farmers regarding the proper drying and storage methods and the serious consequences of aflatoxin contamination. More organizations are now joining the campaign to educate farmers regarding the quality concept like in Gujarat NGOs are joining hands with NRCG to promote the cultivation of Bold seeded groundnuts especially in the Kutch-Bhuj area.

Developing countries mainly face the problem of mould growth and aflatoxin contamination in commodities transported over long distance through the sea route and need immediate attention of the researchers, producers and traders. If the contamination occurs during transit, often no insurance coverage for the risk is available. Because of the different methods of sampling followed in the exporting and importing countries, it is often difficult to define the exact responsibility of the development of aflatoxin as having taken place during transit.

Management of aflatoxin contamination

Following strategies may be followed to minimize the aflatoxin contamination:

  1. The presence of a “natural barrier” to invasion of undamaged pods was also considered and suggested possible antagonism and competition by Trichoderma viridi and Penicillium spp., with in the endocarp community, therefore Trichoderma viridi and Penicillium spp., may be added to the soil at the time of sowing.
  2. Adequate mineral nutrient is important for maximum groundnut production and the factors that increase quality might also reduce contamination. Calcium is the only nutrient that has been shown to have an effect on aflatoxin contamination; therefore gypsum may be applied during flowering phase to the pod zone. Use recommended rate of calcium for location specific application.
  3. Late-season drought stress with soil temperatures 25 to 32°C is by far the most important single determinant of pre-harvest aflatoxin contamination. Therefore late- season drought must be avoided by arranging irrigation.
  4. Soil-inhibiting insects that damage pods, such as termite in Africa and white grab in India, can increase aflatoxin contamination of damaged kernels and infection of undamaged kernels by flavus. These insects may be more active under drought conditions. Therefore every precaution may be taken to control soil-inhibiting insects.
  5. Damaged pods, loose-shelled kernels and immature groundnut are the most likely to be contaminated, so these should be removed by visual inspection manually or by machines, for example the belt-screening technique.
  6. After harvest moisture content of pods must be reduced for safe storage. Drying should be done first in the windrow or following any method suitable to obtain 20 to 25 percent moisture, followed by thin layer or artificial drying to in-shell moisture content of 10 to 11 percent, with in a weeks time.
  7. Moisture content is the single most important variable in stored groundnut. Maximum relative humidity for safe storage is 84 percent at 30°C. This roughly corresponds to a moisture content of 10 to 11 percent in unshelled groundnut and 6 to 8 percent in shelled groundnut.
  8. Groundnut may be stored in atmospheres with low oxygen or high carbon dioxide levels to control flavus growth and insects.
  9. In India during the shelling of groundnut water is sprinkled over the pods to increase the moisture percent to reduce the number of damaged kernels. However, this higher moisture content provides favourable environment for the growth of flavus. Thus adding water at the shelling stage must be avoided.
  10. Edible groundnuts may be sorted by hand on a pick-out table, with electric colour sorters or by a combination of the two. The pick-out may be diverted to oil stock. Careful hand sorting is more effective than colour sorting, so a combination may be preferred. Damaged groundnut pods may be removed by sorting during the shelling or blanching process. These separation methods physically remove the majority of contaminated kernels and improve the quality of the finished product.
  11. Groundnut varieties resistant to flavus invasion and/or do not allow A. flavus to produce the aflatoxins may be developed. At present integrated approach may be followed to prevent pre and post-harvest A.flavus invasion, to minimize the aflatoxin contamination to the prescribed limits.

2.9 Marketing and policies

Marketing practices vary among the developing countries. Within 3 to 4 weeks after harvestime farmers take about 70 to 80 percent of their produce personally to the market to fulfil their cash requirements. The marketable surplus of the small and marginal farmers is so small that they do not find it economically feasible to take it to wholesale markets, even though these distant markets often offer better prices. Rural markets often lack facilities and are generally strips of land serving as a meeting place between buyers and sellers. Market yards are owned either privately or by local governing body called panchayat. In India, marketing period for the rainy season crop commences in October and remains till February, with a peak between November and December. Within this period about 45 percent of the marketable surplus of groundnut arrives in the markets. The disposal of the produce, either at the market or in the village is closely connected with the producers holding capacity. The sales in the village level markets are invariably in the form of pods, while in the assembling markets transactions take place both in the form of pods and kernels. Regulated markets have been organized in some of the main groundnut producing areas, which provide certain amenities to the sellers and forbid exorbitant market charges and malpractice of the traders. The number of regulated markets and the volume of produce passing through them are still inadequate. Please see Figure 32.

 Figure 32:Groundnut is directly being transported from the field to the market yard, Junagadh, India in the month of October.


 aflatoxin contamination

 aflatoxin contamination


India has historically persuaded a policy of self-sufficiency in vegetable oils and related products by banning imports and imposing other quantitative restrictions on trade. These policies kept domestic groundnut prices higher than international prices and consequently depressed the consumption. The government provides support prices for many oilseeds, including groundnut, but these have normally been below market prices and have, therefore, not been effective in procuring supplies. A survey conducted in Gujarat showed that, most of the markets are efficient in pricing for groundnut. As the farmer’s share of the consumer’s rupee is the highest (73 to 79 percent), followed by the miller’s (5 to 8 percent), wholesaletrader’s (1 to 4 percent) and retailer’s (1 to 4 percent). The government procurement has added a new dimension to agricultural marketing and the Primary Cooperative Marketing Societies help farmers to fetch a better price for their produce (Raju and Bhatt, 1985). In Gambia threshing of the crop is carried out in two separate operations; a portion of the crop is reserved for seed is threshed first, bagged and transported to the National Seed Stores, treated with insecticides and stocked. The second threshing operation takes place between December and February. The farm families utilize this portion of the crop in local consumption and surplus is marketed. In Niger the harvest is usually divided into three parts; the largest part is sold, the second is kept as seed for the next cropping season and the family uses the third.

In Senegal the government parastatal SONACOS, which is responsible for crushing and marketing refined groundnut oil, still operates a form of price fixing body through arrangement with licensed private traders. Similarly the Gambian Cooperative Union, a Government parastatal, continues to operate alongside an emerging private sector and dominates groundnut marketing. In Zambia, the National Agricultural Marketing Board continues to enjoy a statutory monopoly, but in practice private traders by informal sector conduct the bulk of groundnut trade. Consequently, market liberalization has little effect on prices. In Malawi the government parastatal ADMARC exerted strong monopoly power during 1980s through an intensive network of rural buying points at which producers were paid guaranteed prices. The sluggish response of the private sectors in groundnut marketing following liberalization in most African countries is due, in part, to high transaction costs. Sudan has implemented very different pricing and marketing policies. The private sector play a dominant role in groundnut marketing policies-producer price support, exchange rate subsidies and preferential export taxes have been used to maintain producer incentives, thus favouring groundnut producers (Freeman, et al. 1999).

The Gambia Produce and Marketing Board (GPMB) have a monopoly over the purchase and export of groundnut. Both the public and private sector carries out the domestic marketing of groundnut. All traders are required to pay farmers the officially announced produce price (Drammeh, 1990). The Ghana Food Distribution Corporation (GFDC), a government marketing and distribution organization buys groundnut from the rural areas and stores for reselling it to the public. GFDC handles only a small portion of groundnut produced and therefore, most farmers depend on middlemen for the ready market. Domestic sector and macroeconomic policies in AGC countries have played critical role in the decline of production and exports by AGC countries. Their combined effect on national groundnut sectors has resulted in average annual changes in AGC-wide groundnut production of 4 percent to 15 percent from the late 1960s to the end of the 1980s. The regional markets have hardly played any role in AGC exports (Atuahene-Amankwa, et al., 1990).

In Zimbabwe farmers in the large scale commercial farming areas were required by law to sell their produce to the parastatal Grain Marketing Board (GMB) at state-controlled prices. These prices did not keep pace with real market prices and their levels relative to other crops, often resulted in swings from one crop to another depending on profitability. This situation led to steady decline in groundnut production in the country. In March 1992 the governmentdecontrolled groundnut marketing producers and permitted to dispose of regulated crops to best advantage. The GMB offers a guaranteed floor price and retains control of imports and exports. Exports are normally permitted only after local requirements are satisfied. A common feature in all major groundnut-producing countries is government intervention through price and marketing policies that directly influence prices and costs. The pattern of intervention, however, is different in developing and developed countries. In the past, in developing countries, the government price and marketing policies discriminated against the groundnut sector by directly suppressing producer prices. In international groundnut oil markets large swings in prices are observed. Such swings become more pronounced in South Asian countries, where domestic production has to be augmented by imports, which fluctuate due to the poor balance of payments position (Rai, et al. 1993).

The role of market places varies not only between developed and developing countries, but also within the developing countries. It depends to a greater extent upon the general socioeconomic and political pattern of the respective region. In developing countries the markets are very important elemental components in the spatial articulation of economic and social activities, their changing role for wholesale and retail trade, in rural and urban environments and for different strata of the population need to be evaluated in the context of the general stage of development in any particular country or region.

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