Aflatoxins are a class of mycotoxins produced primarily by Aspergillus flavus and Aspergillus parasitic group of fungi. The spores of these fungi grow on a suitable food substrate under favourable conditions. Nearly 18 Different kinds of aflatoxins have been identified and the major toxins are Aflatoxin B1 (AFB1), B2 (AFB2), G1(AFG1), G2 (AFG2) and Aflatoxins M1 (AFM1). Both AFB1 and AFM1 are Group 1 carcinogens according to the International Agency for Research on Cancer (IARC). Aflatoxins are especially problematic in dry and hot climatic conditions and their prevalence is aggravated in pre-harvest crops by conditions of drought, floods, delayed harvest, pest infestation, inadequate drying including improper postharvest handling and storage of crops and food.
Types of foods most likely to be contaminated
Agricultural crops such as maize (corn), peanuts (groundnuts), cottonseed, spices, tree nuts and processed products such as milk and milk products, eggs, peanut butter, etc. Contamination of milk with aflatoxin M1 might occur where mammals ingest Aflatoxin B1 contaminated feed, metabolize it in their liver to a hydroxylated metabolite known as ‘milk toxin’ or aflatoxin M1, which is excreted in their urine and milk. Furthermore, it may subsequently also appear in milk products, such as curd, cheese, and milk powder.
Impact of aflatoxins on consumer health
Long-term or chronic exposure to aflatoxins has several health consequences including induction of liver cancer. Aflatoxin also has synergistic effects with Hepatitis B virus infection. Chronic exposure to even low levels of aflatoxin from consumption of contaminated and potential association with stunning immunosuppression. Chronic exposure to even low levels of aflatoxins from consumption of contaminated commodities over a prolonged period increases the risk of liver cancer. It could also contribute up to 30% of all liver cancers globally.
How aflatoxins enter food chain
Aflatoxins producing fungi are normally found on dead and decaying vegetation and infect agricultural crops. Aspergillus fungus can produce aflatoxins in food chain during pre-harvest, harvesting, handling, storage, processing, and transportation. Droughts, high temperatures, low soil fertility, pest infestation affect plant growth and increase the likelihood of fungal infection. Improper storage and delay in drying increases the risks of mould growth and aflatoxin formation.
Regulations have been established in many countries for controlling aflatoxin contamination in food. Internationally, Codex Alimentarius Commission has set limits for mycotoxins including aflatoxins in foods under the “General standard for contaminants and toxins in food and feed (CXS 193-1995)” which serves as the reference standard for international trade in food.
Provisions under Food Safety and Standards Act, 2006
The maximum limits for mycotoxins including aflatoxins are prescribed under Food Safety and Standards (Contaminants, Toxins, and Residues) Regulations 2011, (FSSR). These regulations are available on the FSSAI website www.fssai.gov.in. the table below contains the maximum limits of the aflatoxins in various food conditions as per FSSR.
|Name of the Mycotoxins||Article of Food||Limit µg/kg(max) or parts per billion (ppb)|
|Aflatoxins||Cereal and Cereal products||15|
|Nuts for furthering processing||15|
|Ready to eat nuts||10|
|Oilseeds or Oil Oilseeds for further processing Read to eat||15 10|
|Arecanut or Betelnut||15|
|Ochratoxin A||Wheat, rye, barley||20|
|Patulin||Apple juice and apple juice as an ingredient in other beverages||50|
Test methods for determination of aflatoxins in food
Various analytical methods are employed in the analysis of aflatoxins in food. The analytical methods for aflatoxin determination include Thin-layer chromatography (TLC), High-performance liquid chromatography (HPLC), and enzyme-linked immunosorbent assay (ELISA). The detailed methodology for sample preparation, extraction, and analysis is provided in the Manual for methods of analysis of mycotoxins.
The Manual for methods of analysis of mycotoxins is available on FSSAI website https://www.fssai.gov.in
Can we identify aflatoxin contaminated foods?
Aflatoxins are colourless, odourless and tasteless chemicals which are invisible to naked eye. The mould growth responsible for its production may not only appear on the surface but also penetrate deep into food which may or may not be visible every time. However, the foods showing signs of mouldy growth and having musty flavour shall never be consumed.
Mitigation strategies for prevention and control of aflatoxins in food
Prevention of aflatoxin formation in the supply chain is a challenge but the risk of contamination during food production and storage can be reduced using following mitigation strategies :-
Many of the pre-harvest measures currently available are based on Good Agricultural Practice (GAP), which typically include use of insect-resistant crops, good tillage and weeding practices, appropriate use of fertilizers, good water management, especially irrigation, and crop rotation, etc. Use of biocontrol agents which restrict the growth of aflatoxin producing fungi is considered to be one of the promising measures. This is achieved by introducing a toxigenic (i.e., do not produce aflatoxin) strains of fungi that displace the aflatoxin producers from the fungal communities.
Some of the post-harvest measures are as under:-
- Quickly dry the harvested commodities to adequate moisture levels by using appropriate drying technologies.
- Checking crop moisture using equipment such as moisture meters etc.
- Sorting and removal of the damaged, shrivelled, insect infested and mouldy grains.
- Storing bagged produce on pallets and away from the walls.
- Monitoring and surveillance of aflatoxins in food and feed.
- Highly contaminated crops or foods should be completely destroyed.
Advise to the Consumers
Raising awareness of the dangers of aflatoxins and disseminating relevant information to individuals is an important part of any intervention strategy. To reduce exposure to aflatoxins, the consumers are advised to:-
- Consume well dried, clean and sorted food products free from mouldy growth.
- Discard mouldy, damped, shrivelled and discoloured foods.
- Promote dietary diversification with a view to reducing exposure to aflatoxin contamination.
- Avoid old and damaged bags used for storage as they may be infested with pests.
- Close containers tightly immediately after use and avoid unnecessary stockpiling.
- Examine food well before you buy it. Look at the stem areas on fresh produce, and avoid bruised produce.
- Avoid consumption of broken nuts as they are most likely to contain aflatoxins as compared to whole nuts. Its is also advised not to consume bitter/mouldy nuts
- If bread and top layer of pickles in a container show signs of mould growth, immediately discard the complete product.
- Buy foods which are properly packed and labelled bearing FSSAI Logo. Check “Best before date”, “Use by date” and “Expiry date” of products before consumption.
Advise to Processors/ Manufacturers
- Inspect produce and processing premises regularly. Do not process poor quality, mouldy, weevilled and shrivelled produce.
- Separate the raw material upon receipt, to prevent any cross-contamination during the storage, cleaning, washing and processing stages.
- Inspect and sort the raw materials prior to introduction into the processing line. The inspection may include visual inspection and removal of foreign material.
- Maintain a clean and dry working environment.
- Use good quality processing equipment i.e. Stainless steel.
Analyse microbiological and chemical parameters for raw and processed food products.