Seed screening, grading and packing

1. SEED SCREENING, GRADING AND PACKAGING
Basavaraj Panjagal
Ph.D Research Scholar
Department of vegetable science
K R C COLLEGE OF HORTICULTURE BANGLORE
UNIVERSITY OF HORTICULTUREAL SCIENCES BAGALKOT
Presentation on :
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2. Seed screening
• Removal of any debris or low quality seeds using different screeners
to get good quality seeds
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3. Seed screening meshes
• Many seeds can be screened with several different mesh sizes of hardware cloth.
Hardware cloth is readily available in the following mesh sizes: 1/2", 3/8", 1/4", and
1/8".
• The 3/8" and 1/8" mesh sizes are the most useful sizes, but are the most difficult to
find.
• Aluminum window screen can be used for small seeds.
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4. • screen material it should be mounted on a frame.
• Professional seed screens are mounted on 12" square wooden frames.
• Rough chaff is retained on the top screen, seeds in the middle screen, and
small chaff and small seeds on the lower screen.
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5. The air-screen cleaner
• The air-screen cleaner is the basic machine in a seed-cleaning plant.
• It makes seed separations mainly on the basis of three physical
properties—size, shape, and density.
• The typical air-screen cleaner now found in a farm seed-cleaning
plant is a four-screen machine located beneath a seed hopper.
• Seed flows by gravity from the hopper into a feeder that meters the
seed mixture into an airstream, which removes light, chaffy material
so that the remaining seed can be distributed uniformly over the
top screen.
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6. • The top screen scalps removes large material
• The second screen grades or sizes the seed,
• The third screen scalps the seed more closely,
• Fourth screen performs a final grading.
• The finely graded seed is then passed through an air- stream, which drops the
plump, heavy seed, but lifts and blows light seed and chaff into the trash bin.
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7. Scalper
•
It removes the larger inert matter from the seeds. If it contains a single sieve it
is called as scalpers, two sieves – rough cleaners. The unit consists of a vibrating
or rotating screen or sieve having perforation large enough to allow the rough
seed pass through readily.
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8. Selection of screens
• The two basic screens for cleaning round- shaped seed are a round-
hole top screen and a slotted bottom screen.
• The round-hole top screen should be selected so as to drop the round
seed through the smallest hole possible, and retain anything larger.
• The seed drops through the top screen onto the slotted bottom screen,
which takes advantage of seed shape and retains the round, good seed
while dropping broken crop seed and many weed seed.
• The basic screens for cleaning elongated seed (oats, fescues) are a
slotted top screen and a slotted bottom screen.
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10. Grading
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11. Specific gravity separation
This method makes use of a combination of weight and surface
characteristics of the seed to be separated.
• The principle of floatation is employed here.
• A mixture of seeds is fed onto the lower end of a sloping perforated
table.
• Air is forced up through the porous deck surface and the bed of
seeds by a fan, which stratifies the seeds in layers according to
density with the lightest seeds and particles of inert matter at the
top and the heaviest at the bottom.
• An oscillating movement of the table causes the seeds to move at
different rates across the deck.
• The lightest seeds float down under gravity and are discharged at
the lower end, while the heaviest ones are kicked up the slope by
contact with the oscillating deck and are discharged at the upper
end.
• This machine separates seeds of the same density but of different
size and seeds of the same size but of different densities.
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12. Indented cylinder
This helps to separate seeds according to the length.
• The equipment consists of a slightly inclined
horizontal rotating cylinder and a movable
separating trough.
• The inside surface has small closely spaced
hemispherical indentations.
• Small seeds are pressed into the indents by
centrifugal force and can be removed. The larger
seeds flows in the centre of the cylinder and is
discharged by gravity.
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13. Magnetic separator
The magnetic separator separates seed according to its surface texture or related seed
characteristics.
• First, seed is treated with iron filings, which adhere to rough surface alone.
• The treated seed lot is passed over a revolving magnetic drum and separated from
smooth, uncoated seed.
• It may help to add varied amounts of water while mixing seed and powder,
depending on the seed type.
• At any rate, the effectiveness of magnetic separation depends on the components of
the seed lot and on the powder and water used in the treating operation.
• The greater the difference between surface textures of the seed lot’s components,
more effective will be the separation.
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15. Colour separator
•
The colour separator is used to separate discoloured seed, greatly of lower
quality. Separation based on colour is necessary because the density and
dimensions of discoloured seed are the same as those of sound seed, so
other machines are not effective for separation.
• Electronic colour separation uses photocells to compare the seed colour
with “background” which are selected to reflect the same light as the good
seed
• .Seed that differs in colour is detected by the photo cells, which generate an
electric impulse. The impulse activates an air jet to blow away the
discoloured seed.
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17. • uses an electronic eye that can pick up different colors according to
the way the machine is adjusted.
• As seed falls down a shoot, it passes through the electric eye.
• If the color of the seed is different than the desired color, the electric
eye will activate a sudden burst of air that pushes that seed into a
reject bin while the rest of the seed passes through to another bin.
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18. Friction cleaning
The air-screen combinations cannot remove debris that has a size and density
similar to the seeds. However, if the debris has a different surface texture, it may
be possible to remove by friction cleaning.
• Any object rolling or sliding over a sloping surface encounters a certain friction
depending on the texture of itself and that of the sloping surface.
• Separation is made on a velvet cloth or rubber belt with variable inclination,
which ensures that the slope necessary for the run off of the seed is different
from the slope necessary for run -off of the debris.
• The belt continuously moves upwards and removes the debris while the seeds
roll down the slope.
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19. Spiral separator
•
The separator, which classifies seed according to its shape and rolling ability, consists of
sheet metal strips fitted around a central axis in the form of a spiral.
• The unit resembles an open screw conveyor standing in a vertical position. The seed is
introduced at the top of the inner spiral.
• Round seeds roll faster down the incline than flat or irregularly shaped seeds, which tend
to slide or tumble.
• The orbit of round seed increases with speed on its flight around the axis, until it rolls
over the edge of the inner flight into the outer flight where it is collected separately.
• The slower moving seed does not build up enough speed to escape form the inner flight.
Most spirals have multiple inner flights arranged one above the other to increase the
capacity.
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21. SEED PACKAGING
• Seed packaging is the process of filling, weighing and sewing of bags with seed.
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22. General steps involved
1. Filling of seed bags to an exact weight.
2. Placing leaflets in the seed bags regarding improved cultivation
practices.
3. Attaching labels, certification tags on the seed bags, and sewing of the
bags.
4. Storage / shipment of seed bags.
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23. The factors to be considered
• Kind of seeds to be packed.
• Quantity of seed
• Value of seed (OP or Hybrid)
• Cost of packaging material
• Storage environment in which the packed materials will be held
• Period of storage
• Transport of seed
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24. An ideal storage facility should satisfy the following requirements:
• Maximum possible protection from ground moisture, rain, insect
pests, moulds, rodents, birds etc.,
• Necessary facility for inspection, disinfection, loading, unloading,
cleaning and reconditioning.
• It should protect grain from excessive moisture and temperature
favourable to both insect and mould development,
• It should be economical and suitable for a particular situation
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25. Labelling on package
Quantity: Number of seeds (estimated)
Extraction: Date
Technique of extraction
Fumigation: Date (if undertaken)
Method of fumigation, including chemicals
Drying: Date
Method
Moisture content
Quality: Purity percentage
Number of seeds per unit weight (estimated)
Germination test
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26. Classification
Materials for short-term storage:
Most of these are non-rigid materials such as cotton, burlap, paper, and
composite materials such as multi-wall paper and plastic film, or polyethylene
bags.
• Materials used for short-term storage are generally porous.
• They adequately contain and protect the seeds from mixing, but do not
provide protection from moisture or loss of seed viability.
• Such materials are usually used for mechanically separating seed lots, and
for transporting and shipping seed until the seed can be placed in
environmentally controlled conditions for longer-term storage.
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27. • Burlap bags: greatest strength, can be re-used
many times, and can be stacked high without
slipping of the stack.
Cotton bags: The strength is dependent on the thickness of
the weave and thread, and the quality of the seams. re-
used, depending on the quality of the fabric.
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28. • Plastic bags : Made of plastic material also are
fairly strong but tend to slip when piled.
Moisture impervious but vapour pervious
plastic bags - < 300 guage
Multi-wall bags: Are made of several layers of paper in
a variety of types of construction. They have poor
bursting strength when piled high or accidentally
dropped, and if used repeatedly, they tend to become
brittle along the folds and wear points.
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29. • Cardboard boxes and cans: Though expensive, are re-usable, good for
stacking, and provide some protection against mechanical injury to
seed and to infestation by seed storage insects.
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30. Materials for long-term storage
• Metal and glass containers, properly sealed to prevent the exchange of
moisture and gas, are the most commonly used containers.
• They are the only reliable means of protecting seeds against humidity,
insects, rodents, floods, and mechanical damage.
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31. Vacuum packaging
Vacuum packaging is removing air from the product pouch and hermetically
sealing it. This increases storage or shelf life by inhibiting the growth of
microorganisms and improves hygiene by reducing the danger of cross
contamination. Vacuum packing also preserves protects against
dehydration and weight loss.
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32. Advantages of vacuum packaging:
• A simple solution to packaging goods requiring protection from oxygen
• Positive control of the moisture content of the produce
• Inhibits the growth of aerobic spoilage bacteria
• Lower costs than those of rigid containers
• Longer shelf life for goods
• Disadvantages of vacuum packaging
• It is virtually impossible to remove all the oxygen, since small quantities
will be trapped within cells.
• Microorganisms which are not affected by oxygen are not advantageously
affected by vacuum packing.
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33. • Another material, often used for seed banks, is a heat-sealable
barrier pouch.
• Barrier pouches are a triple-laminate material made from paper,
plastic, and foil. They are sealed with a heat sealer
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34. THANK YOU……
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