TBS/ AFDC 19(290 ) CD 3 
  
 
 
DRAFT TANZANIA STANDARD  
 
Code of p ractice for the prevention and reduction of aflatoxin 
contamination in groundnuts  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
 
©TBS 2021 – All rights reserved  
                                                                            TBS/ AFDC 19(290 ) CD 3 
 Code of practice  for the prevention and reduction of aflatoxin contamination in 
groundnuts   
 
0. Foreword  
 
In Tanzania, groundnut crop is  cultivated and used as important ingredients in complimentary food . 
Furthermore,  groundnuts can  be eaten as snacks  but al so can be processed to be used in food 
industry especially in bakery industries and in domestic as a n ingredient of vegetable sauces, 
smoothies and shakes for texture and flavour.  
 
Unfortunately,  groundnuts are vulnerable to aflatoxin contamination. Aflatoxins  are naturally  occurring  
toxins that  are produced by certain fungi, mainly Aspergillus flavus  and Aspergillus  parasiticus . These 
fungi are considered the most important producers of aflatoxin s in the world’s food supply.  The fungi 
can colonize and contaminate groundnuts  before  and after  harvest, especially following prolonged 
exposure to a high temperature and humid environment, or to stressful conditions such as drought. 
These conditions exis t in Tanzania where groundnuts are predominantly grown by small holder 
farmers and high levels of aflatoxin contamination have been reported.  
 
Therefore,  groundnuts consumers are potentially at risk to acute and chronic dietary exposure to 
aflatoxins. Both acute and c hronic exposure increase liver cancer risk and can suppress the immune 
system . In children  below the age of 5 years, aflatoxin s lead to reduced growth or stunting. High 
doses of aflatoxins cause acute liver cirrhosis leading into illness and even death . 
 
It is urgently needed that the aflatoxin contents in groundnuts are reduced to the tolerable levels for 
protecting public health and promoting the sustainable development of groundnuts value chain. To 
this effect, the code of practice for the prevention and reduction of aflatoxin contamination in 
groundnuts is developed. The recommendations for the redu ction of aflatoxin in groundnuts are 
divided into three parts: Pre -harvest, harvest and post -harvest stage.  
 
This code of practice has been prepared to provide recommendations for all interested parties 
producing and handling groundnuts along the value cha in to ensure its safety and quality for human 
and animal consumption.  
In preparation of this standard considerable help was derived from (CAC/RCP 55 -2014) Code of 
Practice for the prevention and reduction of aflatoxin contamination in Peanuts.  
1. Scope  
This code of practice represents a standard of good practice for the prevention and reduction of 
aflatoxin contamination in groundnuts intended for human and animal consumption along the value 
chain. It recommends practices based on Good Agricultural Pract ices (GAP) and Good Manufacturing 
Practices (GMP) and are generally consistent with Hazard Analysis Critical Control Point  (HACCP) 
principles which are in cooperated  in certification schemes.  
2. Normative references  
The following referenced documents are i ndispensable for the application of this 
document. For dated references, only the edition cited applies. For undated references, 
the latest edition of the referenced document (including any amendments) applies.  
 
TBS/AFDC 19(290)  CD3, Sampling procedures  for aflatoxin analysis in groundnuts  and its products  
TZS 538,  Packaging and labelling of foods  
TZS 740, Raw and roasted groundnuts  – Specification   
                                                                             TBS/ AFDC 19(290 ) CD 3 
 3. Terms and definitions  
For the purpose of this standard the following terms and definitions shall apply:  
3.1 curing  
drying of the in -shell groundnuts to a safe moisture level  
3.2 water activity  (aw) 
water that is not bound to food molecules that can support the growth  of bacteria, yeasts, and fungi  
3.3 mechanical drying  
process of removing water from the groundnut by forcing either ambient air or heated air through the 
groundnut bulk  
3.4 safe disposal  
removal or destroying without compromising health and environmental effect  
3.5 p est 
any organism that damage crops. It can include plant pathogens, insects, weeds, rodents, 
nematodes, birds and parasitic plants  
 
4. RECOMMENDED PRACTICES BASED ON GOOD AGRICULTURAL 
PRACTICES (GAP) AND GOOD MANUFACTURING PRACTICES (GMP)  
4.1 PRE -HARVEST  
For land preparation and crop husbandry practices farmers are advis ed to consult agricultural 
extension services.  
4.1.1 CROP ROTATION  
If possible practice an appropriate crop rotation/sequence to reduce the inoculum in the field which 
may originate from debris remaining after harvest that harbours toxigenic fungal spores . Some crops 
have been found to be particularly susceptible to certain species of toxigenic fungi and the use in 
rotation with each other should be adopted . Crops of low susceptibility to toxigenic fungi such as 
clover, Guatemala ( Panicum maximum ) and othe r legumes can be used in rotation to reduce the 
inocula in the field.  
4.1.2 TILLAGE AND MANAGEMENT OF CROP RESIDUES  
Prepare the seed bed for each new crop by ploughing  under or by destroying or removing old seed 
heads, stalks, and other debris that may hav e served, or may potentially serve as substrates for the 
growth of aflatoxin producing fungi.  However, tilling may not be appropriate with respect to other 
economic and environmental benefits, such as moisture conservation, maintenance of soil organic 
matter, reduced erosion, lower fuel and water use . Hence its costs and benefits should be considered 
prior to application.   
4.1.3  SEED SELECTION/ HOST PLANT RESISTANCE  
4.1.3 .1 Use seeds certified by responsible regulatory authority and avoid farmer saved seeds 
because seeds can be good source of inoculum for aflatoxin producing fungi .                                                                             TBS/ AFDC 19(290 ) CD 3 
 4.1.3 .2 Where possible, grow varieties (cultivars) that were developed and selected for their traits of 
providing at least partial resistance to both non -toxigenic and toxige nic fungi and insect pests and for 
lower aflatoxin accumulation. It is important to plant only those varieties as listed by responsible 
regulatory authority for use in a particular area of a country by virtue of their specific physiological and 
agronomic t raits.  
4.1.4  PLANTING  
4.1.4 .1 Timely planting : As far as practical, crop planting should be timed to avoid high temperature 
and drought stress during the period of seed development and maturation. Predictive models, whe re 
available, should be used as a to ol to plan for the best planting period.  
4.1.4 .2 Planting density:  Ensure appropriate density of planting by maintaining  the recommended 
plant spacing  for the species/varieties grown. Information concerning plant spacing  may be provided 
by seed companies, national authorities /institutes  or extension services.  
4.1.5  CROP MANAGEMENT  
4.1.5 .1 Pest management:  Insect damage and fungal infestation  in the vicinity of the crop  should be 
minimised  by proper use of approved pestici des and other appropriate practices within an Integrated 
Pest Management (IPM) programme. For Tanzania the IPM program for different crops and pests is 
detailed in the National Integrated Pest Management Plan (IPMP). Predictive weather models should 
be used to plan the best application timing and mode of pesticide application.  
4.1.5 .2 Weed Management : Managing weed in  groundnuts by using mechanical methods, registered 
herbicides or other safe and suitable weed management practices.  This is because certain  weed 
species can act as hosts for toxigenic fungi and can increase plant stress  during crop development  
stages especially flowering and podding.  
4.1.5 .3 Irrigation:  Irrigation, if feasible, is recommended to combat heat and drought stress.  It should 
ensure adequate soil moisture during the last 4 -6 weeks of crop growth to minimize pre -harvest 
aflatoxin contamination of groundnuts. This may be achieved by growing a completely irrigated crop 
or by applying supplementary irrigation to a basically rain -fed crop. If irrigation is used, ensure that it 
is applied evenly and that all plants in the plot have an adequate supply of water. Water used for 
irrigation and other purposes (e.g. preparation of pesticide sprays) should be of suitable quality for the 
intended use.   
4.1.5 .4 Fertilizer application:  Soil should be tested to determine if there is a need to apply fertilizer 
and/or soil conditioners to ensure appropriate soil pH and plant nutrition, especially during seed 
development stage of crop growth. F ertiliser should be applied  to provide a balanced mineral nutrient 
supply to produce high quality and quantity groundnuts.  
4.1.5 .5 Biocontrol application:  Where possible , apply biocontrol  method  to prevent aflatoxin 
contamination in groundnuts. Biocontrol products should be applied based on application details as 
approved by authorities . 
4.1.5 .6 Mechanical damage:  Minimise mechanical damage to plants during earthingup, irrigation and 
pest management practices and other farm operations.  
4.2. HARVE ST  
4.2.1 Ideal harvesting time after physiological maturity:  Harvest the groundnuts at full maturity .  It 
is very important to harvest the crop at optimum maturity, as excessive numbers of over -mature or 
very immature pods at harvest can be reflected in h igh lev els of aflatoxin in the product. Also delayed 
harvest of groundnuts already infected may cause significant increase in aflatoxin content of the crop. 
A system by which the growing conditions of the farming crop is monitored (soil temperature and 
precipitation) may be very useful.                                                                              TBS/ AFDC 19(290 ) CD 3 
 4.2.2 Harvesting equipment : Make sure that all equipment, which are to  be used for harvesting and 
storage of groundnuts, are functional. A breakdown during this critical period may cause groundnuts 
quality losses and enha nce aflatoxin formation. Keep important spare parts available on the farm to 
minimize time loss from repairs. Where the equipment needed for moisture content measurements  
are available , should be calibrated.  
4.2.3  Damage during harvesting:  Avoid d amage to groundnuts  at the time of harvest as much as 
possible since this can lead to rapid invasion of the pods by A. flavus/A. parasiticus . Groundnuts 
should be handled as gently as possible . Every effort should be made to  minimize physical damage  to 
groundnuts  at all stages of harvesting and transportation procedures  because it can create an entry 
points of toxigenic fungi . 
4.2.4 Moisture content:  It is recommended to harvest groundnuts with moisture content range from 
25% - 34%. High moisture content will lead t o growth of fungi.  If possible, before harvest inspects  the 
field for fungal (mould) infestation  so that  nuts from the fields with high level of infection, can be 
harvested and stored separately.   
4.2.5  Attack of pest to groundnut plants may cause damage to pods which act as predisposing  factors 
for fungal infections  that are likely to produce aflatoxins. The attacked plants should be harvested 
separately.  
4.2.6 . Groundnut plants that have experienced dro ught stress should be harvested separately to 
avoid mixing  the low risk aflatoxin contaminated groundnuts with those that are potentially highly 
contaminated.  
4.2.7  Where practical, harvest the groundnuts when the soil is moistened to avoid mechanical 
damage to the pods and increase harvest efficiency. After harvest , turn the vines to leave the pods 
uppermost where they are away from the ground and exposed to sun and  wind.  
4.2.8 Avoid piling, heaping, or bin storage of freshly harvested groundnuts for more than a few hours 
prior to drying or threshing to lessen the risk of fungal growth. Ensure that any pile up is not prolonged 
but sufficiently aerated.  
4.2.9 Contain ers and conveyances (e.g., trollies, baskets, farm carts, wagons, trucks) to be used for 
collecting and transporting the harvested groundnuts from the field to drying facilities, should be 
clean, dry and free of crop residues, dust, insects and visible fun gal growth before use and re -use. 
4.2.10 Consignments of groundnuts should be protected from all additional moisture by using 
tarpaulins or covered containers. Avoid temperature fluctuations that may cause condensation on the 
groundnuts, which could lead t o local moisture build -up and consequent ly fungal growth and aflatoxin 
formation . 
4.3 POST HARVEST MANAGEMENT  
4.3.1 DRYING AND CLEANING BEFORE STORAGE  
4.3.1.1  After harvest ensure that all equipment, to be used for drying, cleaning and storage of 
groundnuts, are in a good working order and cleaned to remove crop residues and dust as much as 
possible. A breakdown of equipment during this critical period may caus e quality losses and enhance 
aflatoxins formation. Where possible, make sure that the equipment needed for moisture content 
measurements is available and calibrated.  
4.3.1.2  Freshly harvested groundnuts should be cleaned and sorted to remove damaged nuts a nd 
other foreign matter. Cleaning procedures such as density separators or air legs and slotted screens 
will remove  light pods and pre-shelled kernels  respectively . In this w ay some infected nuts  could be 
eliminated  and safely disposed.                                                                              TBS/ AFDC 19(290 ) CD 3 
 4.3.1.3  Groundnuts should be dried in such a manner that damage to the groundnuts is minimized 
and moisture levels are lower than those required to support fungal growth during storage (refer to 
TZS 740).  To attain that level two methods are recommended which are;  
4.3.1.3.1  Sun and open -air drying : Sun and open -air drying should be done on clean surfaces; to 
the extent possible. Avoid contact of the groundnuts with the soil to prevent the moisture uptake from 
the soil and fungal spores to infect the groundnuts. Dry the groun dnuts on the mats, canvas and 
raised platforms. Groundnuts should be protected from rain, dew, soil, pests, bird droppings and other 
sources of contamination during this process. For more even and faster drying, mix or stir groundnuts 
frequently in thin la yers.  
4.3.1. 3.2 Mechanical drying : Mechanical drying  is preferred  over sun and open -air drying . Flat bed 
and re -circulating batch driers are adequate for small scale operations while using a continuous flow -
dryer is preferred for large scale drying prior t o long storage periods. Avoid d rying too rapidly as this 
may cause skin slippage and off -flavours . Avoid drying at extreme temperature because this may lead 
to production of polycyclic aromatic hydrocarbons (PAHs) and dioxins in the groundnut kernels. When  
curing by supplemental heat, excessive heat should be avoided since this impairs the general quality 
of the groundnuts, e.g. splitting of kernels after shelling. Close checks of moisture content/water 
activity of lots of farmer’s stock should be maintaine d. 
4.3.1. 4 Shelling methods : Shelling should be done in a manner that does not subject the kernels into 
breakage which creates wounds through which a fungus (A. flavus/ A. parasiticus ) can infect and 
produce aflatoxins. Avoid shelling groundnuts when they are heaped direct in contact with soil 
surface.  
4.3.2 STORAGE AFTER DRYING AND CLEANING  
4.3.2.1  Storage premises and containers:  Storage containers should be of food grade  material.  
Stora ge premises and containers should;  
a) provide maximum possible protection from pests such as insect    moulds,  birds etc.; 
b) provide necessary facilities for inspection, disinfection, loading, unloading, cleaning and 
reconditioning ; 
c) protect groundnuts from excessive moisture and temperature favourable to both insect and 
mould growth.  
4.3.2.2  Clean before fill:  Storage containers and premises should be cleaned before filling with newly 
harvested groundnuts. Perforated floors and air ducts also should be cleaned. Spilled and spoiled 
groundnuts in  and around the containers should be cleaned to avoid cross contamin ation and rodent 
activity. Spraying recommended insecticides and fungicides inside the cleaned containers will help to 
eliminate carryover of insect and fungal spores from the previously stored groundnuts . 
NOTE: Use of storage containers and premises after  application of insecticides and fungicides should 
consider withdraw period as provided by manufacturers.  
4.3.2.3  Controlling warehouse condensation:   Warehouse should be built in such a way that it 
does not allow condensation. Painting warehouse roofs wit h white paint reduces solar heat load when 
compared to conventional galvanized material.  Double roofing concept of installing a new roof over a 
defective, existing roof with an air space in -between the two roofs  and the use of air flow controller 
has prove n effective in controlling warehouse condensation.  
4.3.2.4  Clean the groundnuts : Remov e broken and mouldy groundnuts  and other  foreign materials 
before loading into the container   to reduce insect infestation,  nut rot and aflatoxin contamination 
caused by  aflatoxigenic fungi .  
4.3.2.5  Filling of groundnuts  in containers:  Use   groundnuts  spreaders during filling of container to 
help in distributing finely more uniformly and thus will help in reducing the risk of localised hot spot                                                                             TBS/ AFDC 19(290 ) CD 3 
 development. Use of spreaders , however , packs the groundnuts thus increasing resistance to airflow . 
Whenever possible , use air tight containers. Avoid mixing newly harvested groundnuts  with the 
groundnuts  already in the containers/store because it may cause cross contaminatio n inside the 
container .  
4.3.2.6  Avoid stock piling of groundnuts to prevent  heat build -up and moisture accumulation which 
may lead to fungal growth and subsequently aflatoxin contamination. Uniform loading of the 
warehouse allows excessive heat and moisture to escape and reduces favourable areas for insect 
infestation.  
4.3.2.7  Bagged groundnuts:  For bagged groundnuts, ensure that bags are stacked on pallets and 
away from the wall or incorpor ate a water impermeable layer between bags and the floor.  
4.3.2.8  Monitor continuously:  To more effectively monitor the condition of stored groundnuts, it is 
recommended  to measure the temperature, relative humidity and pest infestation in the storage 
facilities and the stored groundnuts at regular time intervals during storage.   
4.3.2.8 .1 Monitoring temperature:  Check the temperature of the storage areas every 2 weeks.  
Temperature rise of 2 -3 °C may indicate microbial growth and/or insect infestation. If the temperature 
or moisture becomes unacceptably high, aerate the groundnuts  by circulation of air through the 
storage area to maintain proper and uniform temperature levels. Turn the groundnuts  inside the 
container (moving from one container to another) to bring the groundnuts  to an average temperature 
inside the container that would eliminate temperature gradients and thus moisture migration.  
4.3.2.8 .2 Monitoring moisture content of groundnuts:  Check the moisture content of the stored 
groundnuts  at a fixed tim e interval. Groundnuts  with a moisture above storage requirement (Refer 
TZS 740) can create an environment conducive to insect and fungal growth development if it is not 
managed.  
4.3.2.8 .3 Monitoring of Relative humidity:  Check the relative humid ity regularly to make sure that it 
is kept below 70  %. Aeration should be conducted during periods of low ambient relative humidity of 
air being forced through the mass of stored groundnuts. Aeratio n during period s of high relative 
humidity can  increase condensation and water activity in stored groundnuts  whose temperature is 
below ambient air temperature. The groundnut can also be transferred from one storage container to 
another to promote aeration  and disruption of potential hot spots during storage.  
4.3.2.8 .4 Monitoring pest infestation:  Avoid pest infestation during storage since they can damage 
groundnuts and also their metabolic activities can increase temperature and moisture hence 
accelerate fungal growth and production of aflatoxin in stored groundnuts. A monitoring program for 
pest should include checking containers on a weekly basis. Visible insects or feeding damage are 
signs of an infesta tion. If spoilage, mould growth or pest infestation in groundnut is observed, 
separate the apparently infected portions of the groundnuts and collect samples for aflatoxin analyses 
by using appropriate s ampling plans as per AFDC 19(291 ) CD2.  
4.3.2.8 .5 Mon itoring aflatoxin contamination:  The aflatoxin level in groundnuts coming into a 
storage and those going out of a storage should be monitored  by using appropriate sampling 
procedures as per AFDC 19(29 1) CD2 and testing methods.  
 
4.3.3 TRANSPORT FROM STORAGE  
4.3.3.1 Cleaning containers:  Transport containers should be dry and free of visible fungal growth, 
insects, and any contamina nt. Transport containers should be cleaned and disinfected before use and 
re-use and be suitable for the intended cargo. Th e use of registered fumigants may be useful. At 
unloading, the transport container should be emptied of all cargo and cleaned as appropriate.                                                                              TBS/ AFDC 19(290 ) CD 3 
 4.3.3.2 Consignments of groundnuts:  Consignment of groundnuts should be protected from all 
additional moisture by  using covered or airtight containers or tarpaulins. Avoid temperature 
fluctuations that may cause condensation on the groundnuts, which could lead to local moisture build -
up and consequent ly fungal growth and aflatoxin formation.  
4.3.3.3 Pest management:  Avoid insect, bird, and rodent infestation during transportation by the use 
of insect and rodent proof containers or insect and rodent repellent chemical treatments provided they 
are approved for the intended use. The use of registered  and recommended  pesticides may be 
useful.  
 
4.3.4 PROCESSING AND CLEANING AFTER STORAGE  
4.3.4.1 Receiving raw materials:  Raw material s should be inspected for its quality and safety before 
processing. Specifications of the raw materials should include a maximum level for af latoxin based in 
appropriate sampling  procedures  as per AFDC 19(29 1) CD 3 and methods of analysis. If raw 
materials received are  unshelled, shelling should be done as in  
4.3.1.4 . Determination of groundnut quality shou ld be done as per TZS 740 . 
4.3.4.2 Sorting and cleaning:  Remove defective (mouldy, discoloured, decayed, shrivelled, insect or 
otherwise damaged) groundnuts  to reduce the level of aflatoxins. Defective groundnuts  should be 
bagged separately and tagged as unsuitable for human  and animal  cons umption. Containers of 
defective groundnuts should be removed as soon as practicable from the processing area. Materials 
which carry the danger of contamination by aflatoxins, or which are contaminated should be safely 
disposed . 
4.3.4.3 Packaging:  Groundnu ts should  be packaged in containers made from food grade packaging 
material and sealed in a manner that will safeguard the hygienic, safety, nutritional and organoleptic 
properties of the product. All bags/cartons should be lot identified as per labelling standards TZS 538 
to facilitate traceability of the product before being moved to controlled storage facilities or 
transported.  
4.3.4.4 Storage and transportation of end product:  Groundnuts that have been processed should 
be stored and transported under co nditions that will maintain the integrity of the container and the 
product within it. Carriers should be clean, dry, weather  proof, free from infestation, and sealed to 
prevent water, rodents or insects from reaching the groundnuts. Groundnuts should be loaded, held 
and unloaded in a manner that protects from damage or water. Well -insulated carriers or refrigerated 
vehicles are recommended for transport when climatic conditions indicate such a need. Extreme care 
should be taken to prevent condensation when unloading groundnuts from cold storage or from a 
refrigerated vehicle. In warm, humid weather, the groundnuts should be allow ed to reach ambient 
temperature before exposure to external conditions. This tempering may require 1 -2 days. 
Groundnuts that have been spilled are vulnerable to aflatoxin contamination and should not be used 
for edible products.