Introduction

Aflatoxin is a toxin produced by fungi from several species of the genus Aspergillus. Aflatoxin is a serious health risk, especially in countries that do not have the means to monitor and limit exposure. Human ingestion of aflatoxin can have both chronic long-term effects and acute short-term effects. Animals are also adversely affected by aflatoxins. Crops containing high levels of aflatoxin are often deemed unsuitable for export, especially to countries with ever-stricter allowable limits. See EDN 87-1 for information, including prevention, detection and removal of aflatoxin.

Aflatoxin—A Cause for Concern  (EDN 87)

By Dawn Berkelaar

Introduction

The term “aflatoxin” refers to several metabolic substances produced by the fungi Aspergillus flavus and A. parasiticus. These fungi are naturally and normally present in soil and in decaying vegetation. A. flavus is found worldwide. A. parasiticus, the main Aspergillus species found on peanuts (groundnuts), can be found in the Americas but is relatively uncommon in Asia.

The majority of aflatoxin is produced by the fungus in the crop or food in which it grows. This means that even though food may not look moldy, aflatoxin may be present in it. Although the opposite can also be true—that Aspergillus mold may grow without producing toxins—this only occurs at temperatures outside their normal growing range. Thus for all intents and purposes, it is safe to say that these toxin-producing Aspergillus species always produce toxins at temperatures within their normal growing range.

Aflatoxins were first discovered in 1960, when more than 100,000 young turkeys, ducks and pheasants in England died from a disease that came to be known as “turkey X disease.” The birds were lethargic, had poor appetites, and died within a week. Examination of the dead birds revealed enlarged kidneys and necrotic (dead) liver tissue. The cause of the disease was found to be toxins in a moldy shipment of Brazilian peanut meal.

There are four aflatoxins that occur naturally: B1, B2, G1, and G2. When a handheld ultraviolet light shines on grain that contains aflatoxins B1 and B2, the grain will look fluorescent blue. Aflatoxins G1 and G2 will fluoresce green. B1 is the most toxic of the aflatoxins. The incidence and ratios of these four aflatoxins vary. For example, the G aflatoxins do not occur in Asia.

Effects of Aflatoxins

1) Effect on Animal Health

Scientists have intensively studied the effect of aflatoxin on animals. Every species of animal tested was sensitive to aflatoxin poisoning, but to different degrees. Aflatoxin has been found to affect pigs, ducks, chickens, turkeys, calves and trout. In chickens, exposure to aflatoxin B1 results in liver damage, decreased egg production, decreased eggshell quality, and an increased susceptibility to disease. Other symptoms in animals include hemorrhaging (bleeding), jaundice (yellow skin) and weight loss. Some general symptoms of animals that eat aflatoxin-contaminated feed on a regular basis include reduced growth rate, a suppressed immune system, and decreased feed efficiency. Aflatoxin is known to cause cancer in animals. It can also prove fatal if eaten by livestock.

2) Effect on Human Health

Aflatoxin is also dangerous to humans. Aflatoxin damages DNA and is among the most potent carcinogens (cancer-causing substances) known. It was labeled as a class I human carcinogen by the International Agency for Research on Cancer (IARC) in 1993 (IARC Monograph 56), and primarily targets the liver. This is because the enzymes that convert aflatoxin to its carcinogenic form are present in the liver in high concentrations. The carcinogenic form causes irreversible genetic damage. Other enzymes convert aflatoxin to less dangerous forms that are excreted from the body in urine and feces. Liver cancer is the most common cancer found in Africa; rates of liver cancer in some countries of Africa and Southeast Asia are 100 times higher than in some northern European countries! However, the lack of data from many countries affected by this problem on the occurrence of aflatoxin contamination makes it difficult to know how widespread is the incidence of liver cancer related to aflatoxin ingestion.

The milk of cows that have consumed contaminated feed has also been shown to contain metabolites of aflatoxin B1 and G1 (metabolites are chemicals left after aflatoxin has been broken down in the body). These metabolites are called aflatoxins M1 and M2, and are probably not human carcinogens (according to JECFA, the Joint FAO/WHO Expert Committee on Food Additives, 56^th meeting, February 2001).

Like aflatoxin, hepatitis B and C are liver carcinogens. A high incidence of hepatitis B occurs in the same hot, humid areas that have high levels of aflatoxin exposure and high rates of liver cancer. Furthermore, aflatoxin is more likely to cause liver cancer when a person has hepatitus B and C. Liver cancer in hepatitis B positive populations [people who test positive for hepatitis B] is 10 to 20 times more likely when they are exposed to aflatoxin.

In addition to cancer, which takes some time to appear, exposure to aflatoxin can cause effects soon after exposure (acute toxicity), including death. In humans, acute exposure to aflatoxin has resulted in jaundice and high blood pressure.

A relationship of some kind seems to exist between aflatoxin and kwashiorkor (a form of malnutrition caused by inadequate protein intake). Children with kwashiorkor have been found to have increased concentrations of aflatoxin in their body fluids than both healthy children and children with other diseases of malnourishment. However, it is not yet known if exposure to aflatoxin actually results in the development of kwashiorkor. The higher levels and more frequent presence of aflatoxin in kwashiorkor patients might mean that they were exposed to more toxins, or it might result from a lack of ability to transport and excrete toxins. If the former is the case, researcher R.G. Hendrickse suggests that aflatoxin may damage the liver, making it unable to manufacture the protein albumin. Low levels of albumin lead to kwashiorkor. Either way, it seems clear that children with kwashiorkor are at greater risk from aflatoxin than normal children. There are also indications that the metabolism of aflatoxin differs depending on the type and incidence of malnutrition. In a study by Hendrickse, a metabolite of aflatoxin B1 was detected in people with kwashiorkor (12%) and with marasmic-kwashiorkor (6%) but only once in a person with marasmus (a form of malnutrition resulting from insufficient energy intake) and not in people with adequate nutrition.

Other factors besides malnutrition can influence a person’s response to aflatoxin. According to an article in the August 2001 issue of Spore, “For those people who do not manufacture a certain enzyme—in Sudan, half the population—…aflatoxins are even more than fifteen times more likely to lead to liver cancer.” Insufficient protein intake also increases susceptibility to aflatoxin.

Spore adds, “The problem is aggravated by the fact that most farmers process lower quality groundnuts [peanuts; lower quality ones are more likely to be contaminated] into groundnut butter for home consumption.”

In addition to its carcinogenic properties, exposure to aflatoxin appears to suppress the immune system. In a study of protein energy malnourished children [children who do not get enough protein in their diet], those with higher aflatoxin concentrations in body fluids had a lower hemoglobin level and increased number of infections. They had also been hospitalized for longer periods of time. In another study, children who had been exposed to aflatoxin suffered from more malaria infections.

3) Issues

Clearly the less aflatoxin that is present in a crop, the better. While monitoring for aflatoxin may not always seem feasible, it is a necessity for those who wish to export crops. Maximum allowable limits have been set for aflatoxin. These differ from country to country, but are becoming stricter.

In the U.S., the current limit for aflatoxin contamination of agricultural commodities (except milk) intended for human consumption is 20 mg of total aflatoxin/kg of product (20 ppb, or just 20 mg/metric ton). Above certain allowable limits, maize (corn) in the U.S. is not even permitted to be shipped between states. These limits are 20 ppb for maize intended for consumption by humans, immature animals and dairy animals; 100 ppb for maize intended for breeding cattle, breeding pigs, or mature poultry; 200 ppb for maize intended for finishing pigs 100 lbs or greater; and 300 ppb for maize intended for finishing feedlot cattle. One part per billion is like one drop of water in a 21,700-gallon (82,135 liter) swimming pool, or like 1 second in 31.7 years!

Recently established standards for allowable aflatoxin limits for the European Union (EU) are much stricter than internationally agreed upon standards. Cereals, dried fruits and nuts intended for direct human consumption cannot contain more than 4 ppb of aflatoxin. [The standard set by the Codex Alimentarius Commission, in contrast, is 15 ppb. The World Health Organization (WHO) and the FAO (Food and Agriculture Organization of the United Nations) consult Codex, which sets international food standards.]. These tighter standards set by the EU will undoubtedly reduce exports of many cereals, dried fruit and nuts from Africa to Europe. Authors of one article estimate that the tighter EU standards, which would “reduce health risk by approximately 1.4 deaths per billion a year, will decrease…African exports by 64% or US$670 million, in contrast to regulation set through an international standard.” (Otsuki et al, 2001. Saving two in a billion. Food Policy 26: 495-514) {mospagebreak title=Susceptible Crops}

Highly Susceptible Crops

Crops differ in their likelihood of aflatoxin contamination. Some of the crops most susceptible to aflatoxin contamination include maize, peanuts (groundnuts) and grain sorghum. These crops are mostly used in animal feeds in the U.S., but are staple crops for humans in many tropical countries. Other major products in which aflatoxin is produced include dry beans, cottonseed, wheat and tree seeds. Rice can also be a significant source of aflatoxin when stored in poor conditions in tropical and subtropical areas.

Copra (the dried white flesh of coconut) often has high levels of aflatoxin contamination. To a large extent it has been replaced by crude coconut oil imports as a source of edible oil. Aflatoxin in the oil is removed during the refining process.

How Much Aflatoxin is Too Much? How Big is the Problem?

Aflatoxin contamination in stored grains is often a huge problem. According to an article in International Agricultural Development (March/April 1996), more than one-third of stored maize in Benin had high levels of aflatoxins during a 1993-1994 sampling period. Contamination levels dramatically increased during storage. Six months after harvest, maize in more than half of the stores was contaminated with very high levels of toxin.

According to an article in Spore issue 94, “In April 2001, high levels of aflatoxins were found in the peanut butter which a South African nutrition programme provided to schoolchildren. A recent study by Ragaa El Hadi Omer in Sudan has shown that poorly stored groundnuts in the country contain twenty times more aflatoxins than the levels permitted by the World Health Organization (WHO).”

In a study of 480 children (aged 9 months to 5 years) across Benin and Togo, 98% had aflatoxin in their blood, with levels highest in weaned children. Children who had stunted growth or who were underweight had 30-40% higher mean concentrations of aflatoxin in their blood than other children.

Some members of our network also shared information about the problem of aflatoxin. Axel Bosselman from Australia shared, “Many years ago I used to work…in the Gambia where aflatoxin has been a real or potential problem ever since groundnuts were planted there and throughout West Africa. [The problem is] usually coped with there by [using] good well-aerated storage to prevent Aspergillus flavus from spreading. (Some years ago, almost all peanut butter in Australia had to go off the shelves because of aflatoxin found in some brands.)” {mospagebreak title=Growth of A. flavus}

Growth of A. flavus and Production of Aflatoxin

The molds that produce aflatoxin can occur both before and after harvest.

1) Preharvest

In some crops, plants are infested with Aspergillus fungi while plants are still growing in the field. Before harvest, one of the most serious causes of contamination is late season drought stress when the soil temperature is between 76 and 90ºF (25 and 32ºC). In peanuts, moisture during the last thirty days is particularly important because it causes contaminated pods to rot and to remain in the soil at harvest. Irrigation, if available, can effectively reduce aflatoxin contamination of peanuts and corn.

Insect damage to pods and kernels can also lead to increased aflatoxin contamination, by providing points of entry for the fungus. This is another reason that management strategies must begin when the plants are still in the field.

After peanuts have been dug, they can fairly safely be placed in inverted windrows for drying. However, they should not be stacked because the peanuts will dry too slowly. Slow field-drying methods allow A. flavus to grow, and peanuts are most likely to become infected during this time of harvesting. Adequate air flow is essential during the initial field-drying period.

2) Storage

After harvest, A. flavus is often found in stored grains, especially in maize and peanuts. A combination of high kernel moisture content (16 to 30 percent), warm temperatures (77 to 90ºF or ), and high humidity (80 to 100 percent) create ideal conditions for Aspergillus to grow and for aflatoxin to form. Improved storage conditions are one of the best long-term approaches to prevent aflatoxin contamination.

The optimal temperature for aflatoxin production by A. flavus is 27ºC (80ºF), though it can occur in a temperature range of 12 to 42ºC (54 to 108ºF). A. flavus requires a relative humidity of 85% in order to grow. This corresponds to different moisture contents in different crops: in starchy cereals, 17.5 to 18.5%; in high oil crops like peanuts, 8 to 9%; and in copra, 5 to 6%.

Localized patches of high moisture and humidity can form in storage (e.g. due to the presence of insects), creating suitable conditions for A. flavus to grow. Under optimal conditions, aflatoxin can be produced within 24 hours and a maximum amount is reached in about 10 days.

Usually when A. flavus is growing in grain, other types of fungi will also be present. However, the maximum amount of aflatoxin is produced when A. flavus occurs alone, as a practically pure culture. If other fungi, yeasts and bacteria are present and growing, little or no aflatoxin is formed or else it is metabolized as it is formed.

Prevention of Aflatoxin Production

Prevention is by far the most practical control strategy to minimize the dangers of aflatoxin.

1) In the field. To reduce mold contamination in the field, you can improve plant vigor by rotating crops; planting at proper densities; and generally controlling pests, especially soil-inhabiting insects.

2) Dry crops quickly. Grain should be properly dried after harvest, as soon as possible and as quickly as possible. Keeping stored crops at the right moisture level can be difficult in high humidity areas, but it may work to dry the seeds carefully and then store in moisture-proof plastic sheeting.

3) Avoid grain damage. A second prevention strategy is to avoid grain damage before and during drying, and also in storage. Insects cause damage to grain, which makes it more prone to fungal invasion. Foreign material and damaged kernels and pods should be removed.

4) Proper storage conditions. A third strategy to prevent the growth of A. flavus is to ensure proper storage conditions. In the tropics, temperatures are generally warm enough for the fungus to grow. Moisture is often slightly easier to control. Ideally, you should use well-designed structures with floors and walls that are impermeable to moisture. In very humid areas, ventilation during the driest part of the day can help reduce moisture. Stored grain requires adequate ventilation, especially if metal containers are used. If available, an instrument for measuring humidity can be helpful to monitor relative humidity in storage.

Sealed storage can be an effective prevention method, as long as temperature fluctuations are minimized and grain is dried properly before storage. Crops generally should be stored or transported in cotton, burlap or paper bags, and not kept in plastic bags.

The form in which crops are stored can also affect the presence and growth of A. flavus and aflatoxin. In one study in Benin, aflatoxin levels were lower in maize that was stored on the cob than in maize stored as kernels.

5) Other prevention measures. There are a few other basic ways to prevent and control aflatoxin in stored crops. Clean grain bins before using them for storage. Monitor bins every few weeks to detect spots of high temperature and high moisture. If you find moldy grain, have it tested for toxins if possible in your area. Separate contaminated kernels, nuts or seeds, and remove foreign matter.

6) Handling of prepared food. Aflatoxin can form on prepared foods, but a few practices can help reduce this kind of aflatoxin contamination. Refrigerate leftovers (if possible), since aflatoxin does not develop under refrigeration. The exclusion of air from foods (e.g. by vacuum-packaging) is another way to minimize fungus growth. Precautions regarding prepared food are important. However, the fungus that produces aflatoxin cannot grow in peanut butter, so levels of aflatoxin in peanut butter would not increase even without refrigeration. {mospagebreak title=Detection of Aflatoxin}

Detection of aflatoxins

Many methods exist to detect aflatoxins. Below is a brief description of some of them.

1) Ultraviolet or ”black” light test

A. flavus fluoresces (seems to glow) bright blue or green under ultraviolet (UV) light (365 nm). However, screening by ultraviolet light is not a conclusive test for aflatoxin. While fluorescence may indicate that aflatoxin is present, it does not necessarily mean that it is. The test uses a long wave UV light in a dark area to detect bright greenish-yellow fluorescence (BGYF) that can indicate aflatoxin contamination. The test actually detects a product of fungal metabolism called kojic acid, rather than the aflatoxin molecule itself. It is called a “presumptive test” and should be used only as a preliminary test followed by more accurate testing to detect aflatoxin. If you use a UV light to test for aflatoxin, you should be aware that both “false positives” and “false negatives” can occur. [For example, rat urine supposedly also fluoresces under ultraviolet light—not that you would want to eat it, either!]

Another shortcoming of the black light method is that fluorescence does not indicate quantities of aflatoxin present. Besides, the fluorescent color may diminish during corn storage although the aflatoxin remains. For best accuracy, the “black” light test should be done on a representative sample, all kernels should be cracked, and the person viewing the sample should be experienced and have perfect color vision.

2) Thin Layer Chromatography (TLC)

There is a TLC method that is accepted internationally (IARC Monograph 56). This is possible to undertake even in rural conditions. Isha with the Auroville Farm Group, a member of our network in Tamil Nadu, India, told us that one of their food processing units for peanut butter relies on TLC to test for aflatoxin. One test sample costs rs 500 (rupees) commercially. For members of the organization a sample costs rs 250 (~US$5.50). 

3) Other Detection Methods

Another detection method includes minicolumn detection. ELISA (enzyme-linked immunosorbent assays) are also used. The latter tests involve a simple extraction procedure, with the extract then being used to react with a treated surface to cause a color change. ELISA tests are relatively inexpensive, easy to use and accurate. Most are “qualitative,” giving a positive or negative reaction.

4) Sampling techniques

When testing for aflatoxin, it is important to use a representative sample. Probe sampling or stream sampling are two good methods. Probe sampling involves the use of a compartmented probe that is inserted into the container to take samples in at least five different locations. Stream sampling is done when grain is poured in a stream during harvesting. A cup is passed under the stream of falling grain at periodic intervals. Whatever method is used, samples should amount to 300 grams or 10 ounces. {mospagebreak title=Removal of Aflatoxins}

Removal of aflatoxins

Much work has been done on the subject of removing aflatoxin from a contaminated crop. David Miller, a toxicologist at Carleton University in Ottawa, Canada, says, “The most important method by far is the physical separation of the infected kernels. That is what is done in the US and this is what is done where there is sufficient crop in developing countries.”

Work has been done to find ways to remove aflatoxin from contaminated products. Blanching and color sorting is possible for peanuts. In the book Peanut Health Management, David Wilson writes, “Blanching to remove aflatoxin contamination is a specialized process during which the peanuts undergo a white roast and the skins are removed. The blanched peanuts are then color sorted. Almost always, the peanut lots that are formed after the final color sort contain very small amounts of aflatoxin because peanuts containing any mold or damage darken during the roasting process, making the final colour sort very efficient. Blanching for aflatoxin removal sometimes results in as much as 25% shrinkage [of kernels], but the residual peanuts are usually free of aflatoxin.”

“Control of Aflatoxin in Raw Peanuts through Proper Manual Sorting ” is a document by Galvez and coworkers, published by the United States Agency for International Development Peanut Collaborative Research Support Program. It describes a method of dry-blanching peanuts that was developed in the Philippines to facilitate sorting of damaged peanuts that are likely to be contaminated with aflatoxin. The method is considered labor intensive for large-scale operations such as those in the United States, where it can be used as a final sort, but is very effective for smaller-scale operations. Machinery including a roaster and deskinner are required for this method. 50 kg of shelled peanuts were dry-blanched at 140ºC (284ºF) for 45 minutes (or up to 55 minutes if the skins still did not come off easily; roasting for too long will cause color change that will make it difficult to see the damaged and discolored kernels). Roasting time depends on the weight of the peanuts to be roasted. Peanuts were then cooled, deskinned and manually sorted for defective, discolored kernels. Dry blanching caused damaged peanuts to appear dark, shriveled and discolored, so that they were easier to pick out.

In experiments, typically no aflatoxin was detected in deskinned unsorted peanuts. In contrast, deskinned sorted discolored peanuts from these batches contained aflatoxin ranging from very low levels to very high levels (as high as 16,000 ppb!). This is because often aflatoxin is found in only a small percentage of kernels, but the concentration in a single kernel may be extremely high. The remaining deskinned sorted peanuts had no detectable aflatoxin.

Dry blanching and sorting added another whole step to peanut processing, but the collaborating company that adopted the technology saw added benefits from it. For example, peanuts no longer had an unpleasant aroma during roasting (perhaps due to early onset of rancidity in unblanched peanuts); the shelf life of products containing peanuts went from six months to 2 years; and demand for the company’s products went up. The company that was unable to export peanut products is now able to successfully export their products containing peanuts.

Aflatoxin is heat-stable, meaning that it is not broken down when food is cooked. Heat will not remove aflatoxin.

An ammoniation process has been developed to inactivate aflatoxin in feed ingredients. However, it is not approved by the FDA for use in food in the U.S., and the process is not always successful in detoxifying aflatoxin-containing seeds.

Treating maize with lye (as is common in Central America) reduces exposure to aflatoxin. However, treating maize with lye is not feasible in areas where water is scarce. Procedures used to process corn help to reduce contamination. Although aflatoxins are generally stable when processing foods, they are unstable in processes such as those used in making tortillas that employ alkaline conditions or oxidation steps. Click here for more information from Cornell.

Oils refined from seeds such as peanuts contain little, if any, aflatoxin. Apparently aflatoxin is separated with the solid fraction when peanuts are pressed for oil. The FDA has agreed that aflatoxin contaminated peanuts may be processed into oil, but the residual meal cannot be used for domestic food or feed unless first tested for contamination. (www.cfsan.fda.gov/ ~comm/cp07001.html). However, according to ICRISAT, peanut oil refined in a solvent-extraction process is free from aflatoxin, but oil processed by village-level technologies may require additional treatment to render it safe for human consumption. (1988. Summary and recommendations of the International Workshop on Aflatoxin Contamination of Groundnut, 6-9 October 1987) [Details were not given regarding what additional treatment is recommended.] {mospagebreak title=Tough Questions}

Tough questions

When thinking about this article, we wondered what kind of advice to give regarding aflatoxin. In particular, we wondered, “Should people overseas ever eat local peanut butter? What advice would you give someone faced with the choice of eating possibly contaminated peanuts or eating nothing at all?”

We heard from some of our network members in this regard, in response to a request in EDN 72 for information about aflatoxins. Jared Barker, Sr., wrote to us from South Cotabato, Philippines. “Aflatoxin is very prevalent here in the Philippines. As you mentioned, it is often found on corn and peanuts plus copra (coconut flesh). [This is] probably an increased problem due to our high rainfall and humidity and our methods of solar drying. It is well known that aflatoxin is a cause of liver cancer. We remember that many years ago, the USAID/US Embassy sent an information letter on this, warning Americans to beware of foods containing the risk of aflatoxin molds. This was not highly publicized, because corn, peanuts and copra are major products in this country.

“The Philippine government through the National Food Authority did research on this subject a few years ago. The agency, NAPHIRE, had a major research project on one of our campuses. They also confirmed the presence of these molds on much of the farmers’ production during the period. We try to be very careful about our source of peanuts and corn grits. Earlier information claimed that the oils from these crops did not contain the aflatoxin; however we have not been able to verify this. We would be interested in further information on this subject. Malignancies of the liver are very common here.”

We also found many cautions in our reading. For example, in a book published in 1975, Clyde M. Christensen commented, “Anyone who travels or sojourns in tropical countries anywhere in the world would do well not to eat peanuts or peanut products in any form, ever.” (“Mycotoxins and Mycotoxicoses: Aflatoxin.” In Chapter 3 of Molds, Mushrooms and Mycotoxins). Aflatoxin is still a huge issue, so that advice would probably be repeated today. [Take note that in the U.S. , Canada , and western Europe, there is essentially no risk of aflatoxin exposure from commercial peanut butter.]

However, the advice above obviously wouldn’t work if peanuts are a staple food in your area, and if you don’t have alternatives. If I knew that the peanuts were sorted using the dry blanch process described above, I would eat them—otherwise I would do my best to avoid them.

Almost every food that you eat contains nutrients that nourish your body as well as toxic factors that have negative effects. Of course you want to minimize the toxins; we hope that this article has given an idea of the seriousness of aflatoxin ingestion, but also some ways to minimize the danger.

Conclusion

Aflatoxin is an extremely harmful toxic metabolite of fungi that grow on different foods. Eating food that contains aflatoxin can lead to health problems, including liver cancer and an increased susceptibility to hepatitis B. Proper storage (as dry and cool as possible) will minimize the growth of the offending fungi. Damaged kernels and seeds are most likely to be infested with aflatoxin, so the best way to ensure that aflatoxin is removed is to mechanically sort the seeds and throw away the damaged ones.

Full references available upon request or from our website (www.echotech.org).

Thank you to Dr. David Miller of Carleton University (Ottawa, Canada) and to Dr. Russell Paterson of CABI Bioscience for comments on drafts of this article. {mospagebreak title=Discussion with Jacque Breman}

A Discussion with Jacque Breman

University of Florida County Extension Director

Several years ago, Jacque Breman visited ECHO. He has worked with groups in Haiti that grow peanuts, and mentioned that in one lot of peanuts, 18% of the lot tested positive for aflatoxin under a black light test. Below is a summary of my discussion with Breman.

DRB: You said 18% of a peanut lot glowed, indicating possible aflatoxin contamination. Is that a serious amount?

JB: Yes! In the U.S., if even one peanut from a sample glows, the whole load stops and the sample is sent to a lab. (USDA standards can be found on the Internet). In contrast, peanuts in storage in Haiti were severely contaminated. 18 of 100 glowed under 110 V UV light. On the island of Gonave, 8% glowed. Peanuts that fluoresce under UV light are not necessarily contaminated with aflatoxin, but some undoubtedly are.

DRB: How can you test for aflatoxins?

JB: The easiest way is to use a 110 V UV light. Contaminated peanuts glow like fool’s gold.

DRB: Why are aflatoxins such a problem?What can be done to reduce them?

JB: Moisture is a huge problem when storing peanuts in Haiti. The humidity in storage areas is too high. There is no moisture barrier against the cement on the floor, so the moisture wicks up into the peanuts. Part of the problem with moisture results because the peanuts are still living and thus they respire moisture.

[In Haiti there are also major problems with Indian meal moth, which has a 14 to 21 day life cycle. Bt has been suggested for treatment of Indian meal moth because Bt is not toxic to people.]

DRB: What ideas can you share to improve storage conditions and reduce aflatoxin contamination?

JB: 1) Put hardware cloth under eaves to keep rats out and screens to keep bats and insects out.

2) Use a moisture barrier between the floor and stored peanuts.

3) Find a way to vent moisture out through the roof. For example, use a black hot pipe in the roof for passively drawing out the warm moist air.

4) Place a fan in the side of the building with a solar panel to drive it.

DRB: What problems exist with post harvest management?

JB: 1) Currently peanuts are dried on the dirt in full sun. They ought to be dried in the shade and off the ground. 2) The nuts, especially those that are to be eaten, need to be graded and diseased ones need to be removed. Currently the damaged and underdeveloped kernels are fed to chickens. When warned about aflatoxins, women who shelled the peanuts said, “Oh that must be why the chickens die when we feed the kernels to them.”!!

*One thing that makes changing production and post harvest practices difficult is that Haitians “live for today because they might not be around tomorrow.”

*Interesting note: Jacque said that cows could handle moldy peanuts because a cow’s rumen breaks down aflatoxin. The ammonia in the rumen chemically breaks the toxin. This sounds similar to the ammoniation process that has been developed to inactivate aflatoxin in feed ingredients (see section “Removal of Aflatoxins”).

DRB: Do you eat peanut butter in Haiti ?

JB: Yes.

DRB: Do some peanut varieties tend to result in a higher level of aflatoxin production than others?

JB: ‘Georgia Green’ is BAD for aflatoxin but produces a high yield. ‘Southern Runner’ gives an 18% increase over Haitian Runner. It has a clean, hard pod and low insect damage. ‘Viragard’ aflatoxin levels were 1.5-3%. Peanuts were left in the ground 1 ½ months.