Recent Methods of Analysis for Aflatoxins in Foods and Feeds
Sampling and Sample Preparation :
Sampling and sample preparation remain a considerable source of error in the analytical identification of aflatoxins. Thus, systematic approaches to sampling, sample preparation, and analysis are absolutely necessary to determine aflatoxins at the parts-per-billion level . In this regard, specific plans have been developed and tested rigorously for some commodities such as corn, peanuts, and tree nuts; sampling plans for some other commodities have been modeled after them. A common feature of all sampling plans is that the entire primary sample must be ground and mixed so that the analytical test portion has the same concentration of toxin as the original sample.
Solid-Phase Extraction :
All analytical procedures include three steps: extraction, purification, and determination. The most significant recent improvement in the purification step is the use of solid-phase extraction.Test extracts are cleaned up before instrumental analysis(thin layer or liquid chromatography) to remove coextracted materials that often interfere with the determination of target analytes.
Thin-Layer Chromatography :
Thin layer chromatography (TLC) , also known as flat bed chromatography or planar chromatography is one of the most widely used separation techniques in aflatoxin analysis. Since 1990, it has been considered the AOAC official method and the method of choice to identify and quantitate aflatoxins at levels as low as 1 ng/g. The TLC method is also used to verify findings by newer, more rapid techniques .
Liquid Chromatography :
Liquid chromatography (LC) is similar to TLC in many respects, including analyte application, stationary phase, and mobile phase. Liguid chromatography and TLC complement each other. For an analyst to use TLC for preliminary work to optimize LC separation conditions is not unusual. Liquid chromatography methods for the determination of aflatoxins in foods include normal-phase LC (NPLC), reversed-phase LC (RPLC) with pre- or before-column derivatization (BCD), RPLC followed by postcolumn derivatization (PCD), and RPLC with electrochemical detection.
Immunochemical Methods :
Thin layer chromatography and LC methods for determining aflatoxins in food are laborious and time consuming . Often, these techniques require knowledge and experience of chromatographic techniques to solve sepatation and and interference problems. Through advances in biotechnology, highly specific antibody-based tests are now commercially available that can identify and measure aflatoxins in food in less than 10 minutes. These tests are based on the affinities of the monoclonal or polyclonal antibodies for aflatoxins. The three types of immunochemical methods are radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), and immunoaffinity column assay (ICA).
Confirmation of Identities of the Aflatoxins :
Although analytical methods might consist of different extraction, clean-up, and quantitation steps, the results of the analyses by such methods should be similar when the methods are applied properly. Since the reliability of the quantitative data is not in question, the problem still to be solved is the confirmation of identity of the aflatoxins. The confirmation techniques used involve either chemical derivatization or mass spectrometry (MS).
Nabil Saad. (2004). Aflatoxins: Occurrence and Health Risks. Retrieved July 4, 2008 from ansci.cornell.edu Website: http://www.ansci.cornell.edu/plants/toxicagents/aflatoxin/aflatoxin.html
Saturday, July 05, 2008
Aflatoxins in human health
Aflatoxins and Human Health
Humans are exposed to aflatoxins by consuming foods contaminated with products of fungal growth . Such exposure is difficult to avoid because fungal growth in foods is not easy to prevent . Even though heavily contaminated food supplies are not permitted in the market place in developed countries, concern still remains for the possible adverse effects resulting from long-term exposure to low levels of aflatoxins in the food supply . Evidence of acute aflatoxicosis in humans has been reported from many parts of the world , namely the Third World Countries, like Taiwan, Ouganda, India, and many others . The syndrome is characterized by vomiting, abdominal pain, pulmonary edema, convulsions, coma, and death with cerebral edema and fatty involvment of the liver , kidneys , and heart.
Conditions increasing the likelihood of acute aflatoxicosis in humans include limited availability of food, environmental conditions that favor fungal development in crops and commodities, and lack of regulatory systems for aflatoxin monitoring and control.Because aflatoxins, especially aflatoxin B1, are potent carcinogens in some animals, there is interest in the effects of long-term exposure to low levels of these important mycotoxins on humans . In 1988, the IARC placed aflatoxin B1 on the list of human carcinogens. This is supported by a number of epidemiological studies done in Asia and Africa that have demonstrated a positive association between dietary aflatoxins and Liver Cell Cancer (LCC) . Additionally , the expression of aflatoxin-related diseases in humans may be influenced by factors such as age, sex, nutritional status, and/or concurrent exposure to other causative agents such as viral hepatitis (HBV) or parasite infestation.
Nabil Saad. (2004). Aflatoxins: Occurrence and Health Risks. Retrieved July 4, 2008 from ansci.cornell.edu Website: http://www.ansci.cornell.edu/plants/toxicagents/aflatoxin/aflatoxin.html
Humans are exposed to aflatoxins by consuming foods contaminated with products of fungal growth . Such exposure is difficult to avoid because fungal growth in foods is not easy to prevent . Even though heavily contaminated food supplies are not permitted in the market place in developed countries, concern still remains for the possible adverse effects resulting from long-term exposure to low levels of aflatoxins in the food supply . Evidence of acute aflatoxicosis in humans has been reported from many parts of the world , namely the Third World Countries, like Taiwan, Ouganda, India, and many others . The syndrome is characterized by vomiting, abdominal pain, pulmonary edema, convulsions, coma, and death with cerebral edema and fatty involvment of the liver , kidneys , and heart.
Conditions increasing the likelihood of acute aflatoxicosis in humans include limited availability of food, environmental conditions that favor fungal development in crops and commodities, and lack of regulatory systems for aflatoxin monitoring and control.Because aflatoxins, especially aflatoxin B1, are potent carcinogens in some animals, there is interest in the effects of long-term exposure to low levels of these important mycotoxins on humans . In 1988, the IARC placed aflatoxin B1 on the list of human carcinogens. This is supported by a number of epidemiological studies done in Asia and Africa that have demonstrated a positive association between dietary aflatoxins and Liver Cell Cancer (LCC) . Additionally , the expression of aflatoxin-related diseases in humans may be influenced by factors such as age, sex, nutritional status, and/or concurrent exposure to other causative agents such as viral hepatitis (HBV) or parasite infestation.
Nabil Saad. (2004). Aflatoxins: Occurrence and Health Risks. Retrieved July 4, 2008 from ansci.cornell.edu Website: http://www.ansci.cornell.edu/plants/toxicagents/aflatoxin/aflatoxin.html
Factors affecting the growth of aflatoxins and the occurance
From my research, i had found that:
Aflatoxins are found in:
In Raw Agricultural Products:
Aflatoxins often occur in plants in the field prior to harvest. Postharvest contamination can occur if crop drying is delayed and during storage of the crop if water is allowed to exceed critical values for the mold growth. Insect or rodent infestations facilitate mold invasion of some stored commodities.Aflatoxins are detected occasionally in milk, cheese, corn, peanuts, cottonseed, nuts, almonds, figs, spices, and a variety of other foods and feeds. Milk, eggs, and meat products are sometimes contaminated because of the animal consumption of aflatoxin-contaminated feed. However, the commodities with the highest risk of aflatoxin contamination are corn, peanuts, and cottonseed.
Factors Favourizing Aflatoxin Production
Fungal growth and aflatoxin contamination are the consequence of interactions among the fungus, the host and the environment. The appropriate combination of these factors determine the infestation and colonization of the substrate, and the type and amount of aflatoxin produced. However, a suitable substrate is required for fungal growth and subsequent toxin production , although the precise factor(s) that initiates toxin formation is not well understood . Water stress, high-temperature stress, and insect damage of the host plant are major determining factors in mold infestation and toxin production.
Similarly, specific crop growth stages, poor fertility, high crop densities, and weed competition have been associated with increased mold growth and toxin production. Aflatoxin formation is also affected by associated growth of other molds or microbes. For example, preharvest aflatoxin contamination of peanuts and corn is favored by high temperatures, prolonged drought conditions, and high insect activity; while postharvest production of aflatoxins on corn and peanuts is favored by warm temperatures and high humidity.
Nabil Saad. (2004). Aflatoxins: Occurrence and Health Risks. Retrieved July 4, 2008 from ansci.cornell.edu Website: http://www.ansci.cornell.edu/plants/toxicagents/aflatoxin/aflatoxin.html
Aflatoxins are found in:
In Raw Agricultural Products:
Aflatoxins often occur in plants in the field prior to harvest. Postharvest contamination can occur if crop drying is delayed and during storage of the crop if water is allowed to exceed critical values for the mold growth. Insect or rodent infestations facilitate mold invasion of some stored commodities.Aflatoxins are detected occasionally in milk, cheese, corn, peanuts, cottonseed, nuts, almonds, figs, spices, and a variety of other foods and feeds. Milk, eggs, and meat products are sometimes contaminated because of the animal consumption of aflatoxin-contaminated feed. However, the commodities with the highest risk of aflatoxin contamination are corn, peanuts, and cottonseed.
Factors Favourizing Aflatoxin Production
Fungal growth and aflatoxin contamination are the consequence of interactions among the fungus, the host and the environment. The appropriate combination of these factors determine the infestation and colonization of the substrate, and the type and amount of aflatoxin produced. However, a suitable substrate is required for fungal growth and subsequent toxin production , although the precise factor(s) that initiates toxin formation is not well understood . Water stress, high-temperature stress, and insect damage of the host plant are major determining factors in mold infestation and toxin production.
Similarly, specific crop growth stages, poor fertility, high crop densities, and weed competition have been associated with increased mold growth and toxin production. Aflatoxin formation is also affected by associated growth of other molds or microbes. For example, preharvest aflatoxin contamination of peanuts and corn is favored by high temperatures, prolonged drought conditions, and high insect activity; while postharvest production of aflatoxins on corn and peanuts is favored by warm temperatures and high humidity.
Nabil Saad. (2004). Aflatoxins: Occurrence and Health Risks. Retrieved July 4, 2008 from ansci.cornell.edu Website: http://www.ansci.cornell.edu/plants/toxicagents/aflatoxin/aflatoxin.html
Saturday, June 21, 2008
Legal limits of alflatoxins
I have research about the limits of alflatoxins, this is another website that i had found, so we can do some comparison.
Legal limits for Aflatoxins require that food for human consumption must contain less than 10mg/kg (parts per billion) of which only 5 ppb may be aflotoxin B1.
The Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act restricts Aflatoxins to a maximum of 50 ppb in animal feed. Exceptions are 20 ppb for lactating cows, calves, pigs, lambs and poultry. Piglets, chickens under laying age and lambs younger than 4 months have a limit of 10 ppb. Feed for cats, dogs, horses and ostriches must have less than 20 ppb. The aflotoxin problem has been extensively researched and these limits have been based largely on research results.
Reference:
Janice Limson. (2001). Maize our Staple Food: Should Toxins Concern us? Retrieved June 21, 2008 from scienceinafrica.co.za Website: http://www.scienceinafrica.co.za/2001/november/maize.htm
Legal limits for Aflatoxins require that food for human consumption must contain less than 10mg/kg (parts per billion) of which only 5 ppb may be aflotoxin B1.
The Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act restricts Aflatoxins to a maximum of 50 ppb in animal feed. Exceptions are 20 ppb for lactating cows, calves, pigs, lambs and poultry. Piglets, chickens under laying age and lambs younger than 4 months have a limit of 10 ppb. Feed for cats, dogs, horses and ostriches must have less than 20 ppb. The aflotoxin problem has been extensively researched and these limits have been based largely on research results.
Reference:
Janice Limson. (2001). Maize our Staple Food: Should Toxins Concern us? Retrieved June 21, 2008 from scienceinafrica.co.za Website: http://www.scienceinafrica.co.za/2001/november/maize.htm
About alflatoxins, its symptoms and limits
This is what i had research on,
I found that:
Aflatoxins, of which aflatoxin B1 (AFB1) is the most important, are produced mainly by the fungus Aspergillus flavus, that may grow on peanuts before or after harvesting and under poor storage conditions.
The tolerance levels of aflatoxins in human foodstuffs are regulated worldwide and in South Africa by Government Notice No. R 313 of 16 February 1990, Regulations Governing Tolerances for Fungus-Produced Toxins in Foodstuffs. According to these regulations, which are the responsibility of the DOH, the maximum legal level of total aflatoxins in foodstuffs is 10 micrograms per kilogram, of which 5 micrograms per kilogram (parts per billion) may be AFB1.
Health implications of exposure to aflatoxins can be divided into symptoms of acute poisoning (aflatoxicosis) and chronic long-term health effects. Although aflatoxins have been implicated in several episodes of acute human aflatoxicosis in various areas of the world, these have been reported at contamination levels in the milligrams per kilogram (parts per million) range, i.e. 1000 times higher than the legal tolerance levels. However, the major health implication and area of considerable international concern with respect to aflatoxin exposure is the cancer-causing (carcinogenic) properties of AFB1, in that long-term exposure to low levels of the toxin may cause liver cancer. This is the reason why aflatoxins are the most widely and severely regulated of all the mycotoxins. It is of great concern that the liver cancer risk increases significantly if a child suffering from hepatitis B virus (HBV) infection consumes aflatoxin-containing foodstuffs, due to the synergism between AFB1 and HBV in causing liver cancer.
The PSNP was launched in 1994, and in areas with poor control over tender specifications and inadequate enforcement of legal levels of aflatoxins in peanut butter during the past 7 years, may have increased the liver cancer risk in millions of previously disadvantaged school children. The risk may have been increased markedly if the children consumed the high levels of aflatoxins quoted in the news media, and particularly if they are carriers and/or subsequently become infected with HBV.
Reference:
South African Medical Research Council. (2008). Alfatoxin in Peanut Butter. Retrieved June 21, 2008 from mrc.ac.za Website: http://www.mrc.ac.za/promec/afloxin.htm
I found that:
Aflatoxins, of which aflatoxin B1 (AFB1) is the most important, are produced mainly by the fungus Aspergillus flavus, that may grow on peanuts before or after harvesting and under poor storage conditions.
The tolerance levels of aflatoxins in human foodstuffs are regulated worldwide and in South Africa by Government Notice No. R 313 of 16 February 1990, Regulations Governing Tolerances for Fungus-Produced Toxins in Foodstuffs. According to these regulations, which are the responsibility of the DOH, the maximum legal level of total aflatoxins in foodstuffs is 10 micrograms per kilogram, of which 5 micrograms per kilogram (parts per billion) may be AFB1.
Health implications of exposure to aflatoxins can be divided into symptoms of acute poisoning (aflatoxicosis) and chronic long-term health effects. Although aflatoxins have been implicated in several episodes of acute human aflatoxicosis in various areas of the world, these have been reported at contamination levels in the milligrams per kilogram (parts per million) range, i.e. 1000 times higher than the legal tolerance levels. However, the major health implication and area of considerable international concern with respect to aflatoxin exposure is the cancer-causing (carcinogenic) properties of AFB1, in that long-term exposure to low levels of the toxin may cause liver cancer. This is the reason why aflatoxins are the most widely and severely regulated of all the mycotoxins. It is of great concern that the liver cancer risk increases significantly if a child suffering from hepatitis B virus (HBV) infection consumes aflatoxin-containing foodstuffs, due to the synergism between AFB1 and HBV in causing liver cancer.
The PSNP was launched in 1994, and in areas with poor control over tender specifications and inadequate enforcement of legal levels of aflatoxins in peanut butter during the past 7 years, may have increased the liver cancer risk in millions of previously disadvantaged school children. The risk may have been increased markedly if the children consumed the high levels of aflatoxins quoted in the news media, and particularly if they are carriers and/or subsequently become infected with HBV.
Reference:
South African Medical Research Council. (2008). Alfatoxin in Peanut Butter. Retrieved June 21, 2008 from mrc.ac.za Website: http://www.mrc.ac.za/promec/afloxin.htm
Friday, May 09, 2008
Some hygiene codes for groundnuts
Hi,
I have loaded some hygiene codes for groundnuts in the blackboard. I'm not sure whether it is needed. I just load it for incase and for your information. Hope that it helps in some ways.
Feel free to take a look.
Thanks,
Vanessa
I have loaded some hygiene codes for groundnuts in the blackboard. I'm not sure whether it is needed. I just load it for incase and for your information. Hope that it helps in some ways.
Feel free to take a look.
Thanks,
Vanessa
Thursday, May 01, 2008
In the shelling plant
From the buying station, the peanuts travel to shelling plants. The peanuts are passed over a series of screens which separate any farm materials such as sticks and rocks from the peanuts and then separate the peanuts by size.
The peanuts are shelled and then inspected by a laser beam and by people to eliminate any immature kernels. The sheller then packs the peanuts into bags, boxes or railcars for delivery to product manufacturers.
In the peanut butter plant
The peanut butter manufacturers inspect the peanuts to ensure high quality then roast them in special ovens which provide an even roast. After roasting, the peanuts are fast-cooled by suction fans that circulate air quickly. Rapid cooling is necessary to halt the cooking process, retain an even color and prevent the loss of too much oil.
Another machine rubs the peanuts gently between rubber belts to remove the outer skin ~ this is called blanching. The kernels are split, the hearts removed and the peanuts are cleaned and sorted a final time.
Finally, the peanuts are ground in two stages (one long grinding would produce too much heat, damaging the flavor of the peanut butter). In the first stage, the peanuts are ground alone. In the second stage, salt, sweetener and stabilizer (to keep the oil from separating) are added.
How It's Made. Retrieved April 27, 2008 from peanutbutterlovers.com Website: http://www.peanutbutterlovers.com/howmade/index.html
From the buying station, the peanuts travel to shelling plants. The peanuts are passed over a series of screens which separate any farm materials such as sticks and rocks from the peanuts and then separate the peanuts by size.
The peanuts are shelled and then inspected by a laser beam and by people to eliminate any immature kernels. The sheller then packs the peanuts into bags, boxes or railcars for delivery to product manufacturers.
In the peanut butter plant
The peanut butter manufacturers inspect the peanuts to ensure high quality then roast them in special ovens which provide an even roast. After roasting, the peanuts are fast-cooled by suction fans that circulate air quickly. Rapid cooling is necessary to halt the cooking process, retain an even color and prevent the loss of too much oil.
Another machine rubs the peanuts gently between rubber belts to remove the outer skin ~ this is called blanching. The kernels are split, the hearts removed and the peanuts are cleaned and sorted a final time.
Finally, the peanuts are ground in two stages (one long grinding would produce too much heat, damaging the flavor of the peanut butter). In the first stage, the peanuts are ground alone. In the second stage, salt, sweetener and stabilizer (to keep the oil from separating) are added.
How It's Made. Retrieved April 27, 2008 from peanutbutterlovers.com Website: http://www.peanutbutterlovers.com/howmade/index.html
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