Post-Harvest Safety Precaution to Maintain Quality

www.iita.orgA member of CGIAR consortium Date: 06-05-2015

Out line
• Introduction
• Postharvest and Losses
• Grain Quality
• Basic concepts of stored grain management
• Time to harvest and requirements
• Moisture content and Drying
• Requirements before, during and after harvesting
• Sampling
• Fumigation
• Cleaning and storage
• Steps for good storage practices

Introduction
• Importance of firm orders
• Supply of sorghum to Factory
• Legume inoculants (Nodumax)
• aflatoxin (deaths)
• Aflasafe demand

Introduction – Health & Economic Losses
• The 2004 outbreak (317 cases reported, with 125 deaths) resulted from widespread
aflatoxin contamination of locally grown maize, which occurred during storage of the
maize under damp conditions. Aflatoxin poisoning likely will continue to be a public
health problem until culturally appropriate storage methods for dry maize are
implemented by the local population
• Evidence that this outbreak resulted from aflatoxin poisoning included:
1. High levels of aflatoxin (up to 8,000 ppb) in maize samples collected from patient
households
2. Clinical illness consistent with acute aflatoxin poisoning
3. Clustering of cases among residents of the same household and
4. Reports of deaths among animals known to have eaten the same maize as the
patients during the same period.
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5334a4.htm.

Introduction – Health & Economic Losses

Introduction – Loss in Trade
Small-scale grain
farmers in Kenya risk
losing out from the
World Food Program
maize purchase deal
due to contamination
of grain by aflatoxin.
On Tuesday, the
government raised
the red flag after
samples from last
season’s harvest
were found to be
contaminated.
http://www.nation.co.
ke/business/Aflatoxin
-to-hurt-farmers-
prospects-/-
/996/918918/-
/f07g2c/-/index.html

Economic Losses
• The National Cereals and Produce Board has re-opened its depots in Eastern and Coast
provinces to buy maize with aflatoxin. A major alert was issued by the government last
week in connection with 2.3 million bags of contaminated maize in the two provinces.
http://www.nation.co.ke/news/Cereals-board-moves-to-buy-bad-maize--/-
/1056/934812/-/5y2gn3/-/index.html
• Change of fortunes as sweet harvest turns suddenly sour
Tests reveal that slightly over 60 per cent of the maize tested in the larger Makueni
District is infected with the poisonous aflatoxin.
http://www.standardmedia.co.ke/article/2000010754/change-of-fortunes-as-sweet-
harvest-turns-suddenly-sour

• Highly toxic metabolite produced
by the ubiquitous Aspergillus
flavus fungus
• The fungus infects crops and
produces the toxin in the field and
in stores
• Fungus carried from field to store
• Contamination possible without
visible signs of the fungus
• Some predisposing factors:
– pre-harvest high temp and
drought stress
– wet conditions at harvest and
post-harvest periods
– insect damage
Aflatoxin Facts

Postharvest and Losses
Postharvest handling is the stage of crop production immediately following harvest
including Drying, cleaning, sorting and packing.
Pre- and Post Harvest losses:
o Pre-harvest losses - before harvesting begins - insects, weeds and pests.
o Harvest losses - beginning and completion of harvesting - losses due to
shattering.
o Post-harvest losses - harvest and the moment of consumption - include on-farm
losses i.e. threshing, winnowing and drying; losses along the chain during
transportation, storage and processing.
o Important in many developing countries are on-farm losses during storage for
consumption or while awaiting selling opportunity or a rise in prices.

What is Grain Quality:
Defined by end user traits and can be categorised as follows:
o Physical: Moisture Content, Test weight, Kernel Size, Total damaged Kernels,
Heat Damage, Broken Kernels, Stress Cracking etc.
o Sanitary: Fungi & mycotoxin count, Insects and insect fragments, rodent
excrements, foreign material, toxic seeds, pesticide residue, odour, dust etc.
o Intrinsic: milling yield, oil content, protein content, hardness, density, starch
content, viability etc.
Nigeria: official standards for grains and oilseeds (NIS 320 1997 ICS 65.060.50. Standard Test Code
for Grain and Seed Cleaners). Can be obtained from Standards Organisation of Nigeria.
At aflasafe SOP Raw Materials (Sorghum) - determine quality and acceptability
of sorghum grains into the plant for the production of aflasafe.

Basic Concepts of Stored Grain Mgt:
o Grain is biologically active and special care required to prevent losses.
o Stored Grain is a man-made ecosystem which attracts pests and rodents, which
can reduce quality.
o Exclude and manage pests.
o Grain quality will not improve during storage.
o Important to understand the initial quality of stored grain.

Time to Harvest & Requirements
o Maize can store for long period of time in unprocessed form
o Its shelf life greatly depends on the prevailing ambient temperature and
relative humidity, and other factors like the inherent moisture, pests and
diseases.
o Recommended PHH and mgt operations involve the manipulation of the
above factors in order to obtain high quality maize grains.
o Quality control starts with harvesting. Optimum time when the stalks have
dried and MC about 20-17%.

Moisture Content & Tests
Moisture content
Definition
It is the amount of moisture (water) the seed contains.
2 methods of expressing moisture content:
1. Wet Basis
2. Dry Basis
Moisture content determination methods:
1. Direct methods determine the amount of water in the seeds
by removing them.
2. Indirect methods require the use of a meter to measure the
property of the seed that can be related to the moisture
content

MC, Temp & Storage Period
Source: Transactions of ASABE 3330337

Grain drying
o Physiological maturity - high moisture e.g. maize 35 %, highest quality, greatest
vigour and germination potential.
o Duration of safe storage dependent on the condition the crop was harvested
and the type of storage facility being utilized.
o Drying - Removal of high moisture to low levels for safe storage.
Drying, Aeration and Dehydration.
Drying permits a reduction of losses in storage from causes such as:
• Premature and unseasonable germination ,
• Development of moulds,
• Proliferation of insects.
Recommendation: Harvesting early MC >20%, quickly dry to safe MC <13%.
Drying may be effected by any of the following methods:
1. Field drying
2. Sun drying
3. Drying with forced artificially heated or unheated air,
4. Use of desiccants to dehumidify the air and
5. Drying with infrared light rays.

Reasons for drying.
o Retard or stop the development of bacteria, fungi, mites and
insects during storage.
o Make further processing easier.
o Prevent germination.
o Produce uniformly high quality crop/seed with high vigour and
germination.
o Reduced damage in processing operations, especially in
shelling in the case of maize, to elevators and cleaners.
o Increased quality of harvested grain by reducing crop
exposure to weather.
o Harvesting can be done early and in a controlled way.
o Harvesting operations can be scheduled to obtain more
efficient use of labour and available equipment.
o Allows more time for post-harvest fieldwork.
o Reduced potential for weather and pest related field losses.

Drying Methods

Importance of drying
http://www.nation.co.ke/news/regional/Sh760m-given-to-fight-maize-poisoning-/-/1070/936196/-/h322gm/-/index.html

Requirements during the Harvesting
o Harvest as soon as it is dry but not overstay in field because of attack by weevils
and lodging. In addition to reducing post harvest losses, this will also release the
field for early land preparation.
o Keep the grain as clean as possible. Dry maize on cement floor or use tarpaulin to
reduce chance of contamination.
o At home, do not first heap the cobs in any room, kitchen or in the yard because
this will expose them to all the dangers that cause post harvest losses.
o Transfer them to the drying place (like the crib) immediately.
o Dry on concrete or canvas not on bare soil

Before, during and after harvesting
Before Harvesting:
o Ensure the drying place or equipment is clean and disinfected, ready to receive
the cobs.
o Remove old grain and dirt from contact with the good or new grain. This
includes harvesting tools, carts, wheel barrows, bags and baskets.
o Where possible, fumigate them or at least treat them with boiling water to kill
insects or their eggs. This is done in order to avoid infection of new grain by
insects and their eggs.
Harvesting
o Harvest and transport to crib without putting on soil to avoid contamination.
After Harvesting
o clean all the materials used in the process of harvesting and store them
properly, away from sources of contamination and insect breeding places.
o The same materials may be needed during the proceeding operations e.g. to
transport cobs from the crib for threshing or to transport grains to the store.
They can easily contaminate clean grains or become source of pest.

Sampling
Sampling is important for checks and testing for a range of
properties; moisture content, infestation viability, weight etc.
• Done periodically to check on the viability and general
deterioration of the crop.
1. In the field to determine MC, maturity, infestation etc.
2. On arrival at the store for MC, infestation, quantity etc
3. During storage for continual quantity monitoring
4. On despatch from store where it is weighed out and samples
retained in event of subsequent disputes
5. On arrival at the purchaser’s store for required quality attributes.

Sampling
Sampling points: A 5; B 8; C 11.

Sampling

Fumigation
o Fumigation - method of pest control that completely fills an area with
gaseous pesticides or fumigants to suffocate or poison the pests within.
o Used for control of pests in buildings (structural fumigation), soil, grain, and
produce & during processing of goods to be imported or exported to prevent
transfer of unusual organisms.
o It involves:
o Covering the area to be fumigated to create a sealed environment;
o Releasing of fumigant into the space to be fumigated;
o Holding the pace for set period while the fumigant gas percolates through
the space and acts on and kills any infestation in the product and finally
o Ventilation of the space to allow poisonous gases escape and render it safe
for entry.
o If successful, the fumigated area is now safe and pest free.
o Widely used fumigants include:
Phosphine, 1,3-dichloropropene, chloropicrin, methyl isocyanate, hydrogen
cyanide, sulfuryl fluoride, formaldehyde, Iodoform

Fumigation

Cleaning
• After threshing, grains (or shells, in the case of groundnuts) are contaminated by
impurities (earth, small pebbles, plant and insect waste, seed cases, etc.)
• These impurities hinder drying operations and make them longer and more costly.
• Traditional methods: Simplest cleaning method, known as winnowing, consists of
tossing the grain into the air and letting the wind carry off the lightest impurities.
• Although widespread does not eliminate all impurities.
• Air Screen Cleaning:

Storage
• Storage - produce kept in condition to guarantee food security
other than during periods of agricultural production.
• Main objectives of storage:
i. At the food level – use on annual/multiannual
ii. At the agricultural level –Availability of seed for crop cycles
to some
iii. At the agro-industrial level - guarantee regular and
continuous supplies of raw materials for processing industries;
iv. At the marketing level - to balance the supply and demand
of agricultural products, thereby stabilizing market prices.
• To attain above general objectives, necessary to adopt
measures aimed at preserving the quality and quantity of the
stored products over time.
• Storage in bag or bulk; sealed or unsealed structure.
• Effect of environmental factors and Agents causing deterioration
– microorganisms, insects and rodents

Storage
• Influences of environmental factors
• long-term storage, degradation processes must be slowed down or even
stopped.
• Degradation of grains during storage depends principally on a
combination of three factors:
o Temperature,
o Moisture,
o Oxygen content.
• Temperature and moisture
• Direct influence on the speed of development of insects and
microorganisms (moulds, yeasts and bacteria), and on the premature
and unseasonal germination of grain.
• Moisture content of stored grain, depends on the relative humidity of the
air,
• Temperature sensors in silos

Storage
• Oxygen content
• Like grain, micro-organisms and insects are living organisms that need
oxygen. Storage of grain in places that are low in oxygen causes the
death of insects, cessation of development of micro-organisms, and
blockage, or slowing down, of the biochemical phenomena of grain
degradation. This favours the conservation of grain, but may affect its
germinating power. CA Storage.
• PICS bag storage - Purdue Improved Crop Storage (PICS2) -
http://www.entm.purdue.edu/PICS2/

Ideal Storage Conditions

Ideal Storage Conditions
Figure 2. Storage Risk Increases with Temperature, Moisture and Time.

Steps for Good Storage Practice
Pests
Stored product pests can be managed either behaviouraly (traps ) or with
several preventive and curative measures (both chemical and non-
chemical methods).
Steps.
1. Before storage
• Check for leakage of rain water and sufficiency of drainage facilities
• Cleanliness of the facility and environment
• Pesticidal treatment – e.g. application of Actellic dust
• Security and fire fighting arrangements and
• Repairs to available equipment
2. After receipt
• Inspection for variety and soundness of quality
• Carefully inspection for infestation and when present, type and extent of
infestation,
• Inspection whether grain has excess moisture, any grain rendered wet or
damaged to be segregated and salvaged with facilities available and
check the weight received

Steps for Good Storage Practice
3. During storage
• Maintenance of cleanliness
• Ensuring aeration where necessary
• Check for leakage after rains
• Inspection for insects, rats and mites at fortnightly intervals
• Watch for advancement in deterioration, if any,
• Arrangement for segregation, salvage and processing, wherever,
damage owing to leakage of water and other causes might have
taken place.

www.iita.orgA member of CGIAR consortium Date: 02 – May - 2013

Post-Harvest Safety Precaution to Maintain Quality

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