This course provides an overview of the issue of postharvest loss of grains by exploring essential physical, technical, and social dimensions of postharvest supply chains and loss prevention methods globally. Each year, estimates suggest that 1/3 of all food produced is lost or wasted, making postharvest loss a critical global food security and sustainability issue of today. Key knowledge areas are presented including: -An overview of postharvest loss -Supply chain activities such as harvesting, drying, and storage -Economics and markets -An introduction to the network of actors working in this field We face the immense challenge of feeding over 9 billion people by the year 2050. To meet these demands, yields will have to more than double using the same amount of natural resources. In recent years, postharvest loss has been recognized by major institutions including the US government, the United Nations, the CGIAR Research Consortium, and several others as a significant opportunity to impact food security and improve livelihoods. Despite this increased attention, a lack of knowledge, technical capacity, and resources remain obstacles for stakeholders worldwide to act on these issues. This course will, for the first time, provide you as professionals, practitioners, and students, with a comprehensive introduction to postharvest loss processes and begin building capacity for loss prevention worldwide.
2.3. Grain Storage and Management
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En provenance du cours de University of Illinois at Urbana-Champaign
Global Postharvest Loss Prevention: Fundamentals, Technologies, and Actors
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University of Illinois at Urbana-Champaign
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Week 2: Causes: Major Causes & Encounters for PHL
This module will introduce you to technical, social, and economic factors and situations that lead to postharvest losses. Harvesting, drying, and storage phases will be specifically covered as stages that are both vital in the grain supply chain and in which a great deal of postharvest losses are experienced.
Rencontrer les enseignants
Dr. Prasanta KalitaDirector of the ADM Institute for the Prevention of Postharvest Loss
Department of Agricultural and Biological Engineering
Hello everyone.
My name is Vijay Singh.
I'm a professor in department of Ag and Biological Engineering, and
my lecture today is on grain storage and management.
So, in most parts of the world zero grains are produced on a seasonal basis,
and in most countries there's only one crop that's produced.
What that means is that in order to consume or process grain year round.
It must be held in storage for various lengths of time.
The market for grain is fairly stable in demand but widely fluctuating in supply.
The main function of storage is to even out that variation.
That fluctuation in the market demand.
By taking the produce off the market in surplus years and
putting it back in the lean seasons.
We can even out that fluctuation in the grain market price.
The improper grain storage can result in spoilage.
There can be insect or mold damage during improper storage.
All right, grain storage losses vary depending upon grain conditions,
environment, and storage techniques.
This is the total waste loss provided by World Resources Institute
in 2011, and we can see the red bar is the storage losses.
We can see that these storage losses vary by location, from 6% in
North America to as high as 37% in sub-Saharan Africa.
Factors affecting grain losses.
In this lecture,
we'll cover some technical issues of grain storage including storage structures,
grain moisture content, storage temperature, and grain pests.
Mainly insects and grain molds.
The purpose of storage structure is to protect the stored grain from weather,
insect, birds, and rodents.
In developed countries, grain is usually stored
in large round metal bins and concrete silos.
Where is an developing countries, grain is usually stored in small bags,
clay bins, or some baskets.
So, here are different storage conditions in different parts of the world, and
this is one from the developing countries.
As we can see here, grain is stored in jute bags,
in plastic bags, in baskets, open-air storage or
in small metal bins, which is getting very popular in Asia primarily in India.
If you look at storage structures in developing countries,
you can see this steel silos, concrete silos, or warehouses.
Next is something very important for grain storage, and
that is grain moisture content.
It is the most important factor for grain storage.
Without proper moisture, grain can never be stored safely.
High moisture content and temperature mean faster growth of molds and
more rapid grain spoilage.
Reduction of even 1% of
grain moisture content can roughly double the grain storage life of seeds.
Next slide is the recommended storage moisture content of
different cereal grains and legumes.
If we store these grains for less than six months,
corn can be at 15% moisture content, but
if the storage time is longer than six months.
It has to be at 13% moisture content.
In case of beans, soybeans.
The moisture content has to be 13% for storage less than six months, and
11% for storage more than six months.
And you can see mostly it is about 13 to 15% moisture content for six month
storage, and about 8 to about 13% moisture content for longer than six month storage.
Temperature's another important factor for grain storage.
It is very closely related with the activities of microorganisms and insects.
The optimum temperature for the most species,
insect species range between 25 to 32 degrees Centigrade.
Increase in five degrees Centigrade
in temperature can roughly half the seed storage life.
Now let's look little more carefully on the grain temperature and
its effect on storage.
So here in this figure is insect activities at
different temperature ranges.
For most of the time temperature rises as temperature rises in grain during storage.
Usually that means increased risk for insects of molds in the grain.
Most insects are sensitive to temperature.
The temperature of about 20 to 30 degrees Centigrade is most favorite temperature
for insects.
And as the temperature decreases, the insect activity decreases accordingly.
And eventually,
around five degree Centigrade or freezing point most of the insects will die.
Here is just a simple depiction of how
corn is stored in the state of the start silo facilities.
In most of the modern seed storage or grain storage.
We have these cables that routinely monitor the temperature of the grain,
and if the temperature of grain increases the aeration of the fan is turned on,
which allows the aeration of the grain and cools it down.
And thus, bringing the temperature of the grain down
in order to prevent any activity by insects.
Next we'll talk about grain pests.
Grains are stored for a period ranging from several months to more than a year.
And regardless of length of storage,
grain pests can invade the stored grains and affect its quantity and quality.
The most common grain pests are molds, insects and rodents.
Other losses can be caused by mites and birds.
The degree of the pest activity
in stored grain is affected by grain moisture content.
Grain temperature, grain type, grain damage, history and other factors.
Grain molds.
Among grain pest, mold damage is often the most difficult to assess.
This figure shows two popular molds found in grain.
One is penicillin, other one is aspergillus.
Molds are multicellular plants consisting of branching,
intertwined filaments called hyphae.
Molds are dangerous and harmful to grain
since we cannot observe them visually and they spread very quickly.
Over 100 mold species have been isolated from grain.
However, some invisible mold growth may have also occurred.
Culturing for mold on proper medium can reveal the kind and
the number of the mold.
Accurate, but requires about five to 14 days.
Field molds.
Some of the mold may develop on the grain when the crop is in the field.
Such fungi are called field molds.
It usually happens under high moisture and high temperature conditions.
Usually it requires high equilibrium relative humidity,
about 95 to 100%, and it's difficult to prevent field molds.
There's another kind of mold called a storage mold.
Storage mold seldom affects grain in field, but in storage periods.
Unlike the field mold,
the storage mold grows at equilibrium relative humidities below 95%.
The minimum relative humidity requirement for
the most storage molds are between about 70 to 90%.
The common storage molds are several species of Aspergillus and
Penicillium, each has different relative humidity requirements.
And it's development is thus an indicator
of the moisture content of the stored grain.
Grain damage.
Mechanical harvesting of grain at high emotional content often results in
physical damage of kernel in forms of kernel breakage, and cracked seeds.
Broken, stress, cracked, and otherwise physically damaged kernels
are more readily susceptible to more damage than undamaged kernels.
Several grain molds produce toxins called mycotoxins.
The most common mycotoxins are aflatoxins, fusarium toxins, and ochratoxins.
Of these, the aflatoxins are of greatest importance to grain storage environment.
Aflatoxin is produced by strain of Aspergillus flavus and
Aspergillus parasiticus.
It's extremely toxic and has been shown to cause cancer in certain cases.
Because of extreme toxicity,
the tolerance of presence of aflatoxin in US is zero for food destined for
human consumption, and 20 parts per billion for feed grains for animals.
More than 12 different aflatoxin derivatives have been identified.
Aflatoxin B most frequently occurs in grain.
The figure shows the molecular compound of Aflatoxin B and
other Aflatoxin derivatives.
How do we detect mycotoxins?
We can do quick tests.
We can do screening procedures, and then we can do quantitative tests.
The best way to definitively identify mycotoxin is to use HPLC,
or high-performance liquid chromatography in order to detect these mycotoxins.
HPLC stands for high-pressure liquid chromatography.
What you do is you inject a sample through a column and
the column has a particular chemistry.
And depending upon what is inside the sample that was injected.
It reacts with the column chemistry, and
as a result we are able to spread out the different constituents inside the sample.
As these constituents start to come out at different times,
they are then detected by an optical instrument.
It can be a refractive index, a detector.
It can be a UV detector.
It can be all kinds of different detectors that can be used
in order to identify these constituents, and that's what an HPLC is.
The last thing that we'll talk about are the grain insects that affect
the storage grain.
Insects are the major grain pests, especially in tropical and
subtropical regions.
The damage caused by insects can be bored holes in kernels.
Injury to the germ, or the embryo part of the corn kernel.
Heating and subsequent condensation, causing molding and
contamination of the grain.
How can we prevent insect infestation?
Remove all the grain and grain debris from the bin before harvest season.
Treat the inside of the bin with proper chemicals at least twice a week.
Use grain cleaners,
use grain spreader to evenly distribute the fine material and store dry grain.
Cool the grain by aeration or chilling.
Monitor the temperature and moisture content of the grain.
Aerate the grain when necessary.
Clean and sell, or fumigate, immediately after insects are discovered.
Last thing is the aeration.
Aeration is the process of moving ambient air through the stored grain.
The main purpose of aeration is to decrease or
increase the grain temperature to the desired level.
Only a minor amount of moisture is removed from grain during aeration cycle,
usually less than 0.5%.
One of the most important processes in grain storage management is aeration.
Finally, we have some references related to storage of grains and
to prevent quality losses.
Thank you very much.
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