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Pre storage treatments of fruits and vegetables
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What are pre-storage treatments?
These are the treatments given to a commodity
(fruits and vegetables in present context) generally
after harvesting to reduce postharvest losses,
enhance storage life and retain quality.
Any examples of pre-storage treatments?
o Cleaning
o Washing
o Sorting
o Grading
o Waxing
o Packing
o Pre cooling
o Curing
o Desapping
o Chemical treatments
o Irradiation
o Vapour heat treatment
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1. Cleaning
This is a treatment given to remove adhering dust, dirt,
extraneous matter, pathogenic load etc. from the
surface of a commodity. Cleaning basically sanitizes
the produce and avoid entry of undesirable contents to
enter the packaging and storage line.
Cleaning is a broader term and includes,
dusting, washing etc.
Methods of cleaning
i. Dry method (Dusting etc.)
ii. Wet method (Washing)
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i. Dusting
This method is mainly used to remove the adhering
soil, etc from commodity i.e. potato, root vegetables,
carrot, radish etc.
Dusting helps to shed undesirable load (weight)
of the commodity and thus reduce
transportation cost.
It also removes pathogenic microorganisms
present in the soil from the surface of the
vegetables.
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ii. Washing
This method is used in most fruits and vegetables.
Washing is done at the pack house through automated
washing system fitted with overhead sprayers and
smooth rotating brushes to clean and wash the fruits.
Washing with clean water mixed with a neutral
detergent such as Teapol, Sandovit or Indtron at
0.1% (1 ml / litre of water) is effective.
The process of cleaning and washing will take
3-5 minutes. The temperature of water should
be at room temperature (270C).
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2. Sorting and Grading
This may be done manually or by using a machine.
Fruits are graded on the basis of their colour, size and
weight and sorted for freeness from damage/ diseases.
At the sorting and grading table, trained workers
wearing gloves sort out the oversized and
undersized fruits, immature/scarred/blemished
fruits, diseased/insect damaged fruits and as
well as fruits with sap injury (in mango) under
the supervision of quality supervisor.
The segregated fruits in the grader machine kept in
plastic crates are removed at the end each working
shift from the process area and are distinctly labeled
for disposal.
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Difference between sorting and Grading
Sorting Grading
1. Undesirable type of fruits i.e.
diseased, damaged, deformed
are removed
1. Fruits and vegetables are
categorized according to
difference in their weight, size,
colour, maturity etc.
2. Done primarily to reduce
spread of infection to other fruits
2. Done to fetch better price in the
market.
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3. Waxing / Coating
It is the process of applying wax on the surface of
commodity by spraying, dip or immersion, brushing,
fogging or foaming.
Some fruits develop natural fruit wax on their
surface at the time of maturity. i.e. plum, apple,
citrus, grapes etc.
This has its role in reducing water loss fro the
commodity and thus reducing shriveling and weight
loss. While handling care is taken to touch the fruits as
minimum as possible to retain as much of the natural
wax (also called bloom) on the fruit.
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Advantage of Waxing
Improve appearance of fruit
Reduce moisture loss by 30-50% and retards
wilting/ shriveling
Heals minor injuries
Protects fruits from minor infections
Provides modified atmosphere and
increase shelf life
Acts a carrier for various chemicals etc
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Types of waxes
Paraffin wax, carnauba wax, bee wax etc
Examples of some commercial formulations:
Tal-Prolong, Semper Fresh for apple, Frutox,
Waxol, Nipro fruit wax for apple, and citrus,
Ban seel for banana, Nu-coat flo for citrus,
Brilloshine L for apples, avocado, melons
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4. Pre-cooling
It is the prompt cooling of the commodity
immediately after harvest (generally within 24
hrs of harvest), to its safe storage temperature ,
which aims at removal of field heat.
Rate of cooling depends on
Initial product temperature
Rate of flow of cooling media around the commodity
Temperature difference between produce and cooling media
Thermal conductivity of produce
There are different
cooling methods followed for different commodities. Some
fungicides may be mixed in water during hydro-cooling to reduce
decay incidence Weight loss during forced air cooling can be
reduced by maintaining high (95%) relative humidity in the pre-cooling
chamber
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5. Chemical treatment
Various chemicals are applied to fruits and
vegetables in order to control postharvest
diseases and pest infestations.
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Dipping:
The commodity is immersed in water
containing appropriate concentration of
chemical which is toxic to the pathogen.
However, the concentration of chemical should not be toxic
to the fruit/ vegetable and should not endanger public health.
For improving the efficacy of the dip treatment and better
surface coating some wetting agents may also be added.
The effectiveness of the fungicidal solution may also be
enhanced by hearting the water in which the fruit is being
dipped.

5. Chemical treatment
Various chemicals are applied to fruits and
vegetables in order to control postharvest
diseases and pest infestations.
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i) Dipping:
The commodity is immersed in water
containing appropriate concentration of
chemical which is toxic to the pathogen.
However, the concentration of chemical should not be toxic
to the fruit/ vegetable and should not endanger public
For improving thhee aelftfhic.acy of the dip treatment and better
surface coating some wetting agents may also be added.
The effectiveness of the fungicidal solution may also be enhanced
by hearting the water in which the fruit is being dipped.
500 ppm of benomyl in water at 50-55 min, for 2 to
15 min is effective for controlling anthracnose in
mango without damaging the fruit.

ii) Cascade application:
Commodity is passed below a shower of
shower of diluted chemical.
iii) Electrostatic sprays:
Applying the chemical as a spray but producing very fine
particles and then charging them in an electrostatic sprayer
so that they readily stick to the commodity underneath them.
The fine droplets of chemical solution have same charge
and thus they repel each other and are attracted towards
earth during field sprays.
iv) Dusting:
Active chemical is diluted with an inert powder i.e.
talc for uniform application and reduced wastage.
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Sulphur dioxide fumes are sued for
controlling postharvest diseases in grapes.
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v) Fumigation:
vi) Chemical pads:
Paper pads impregnated chemical are used
for wrapping the fruits and vegetables and
control postharvest diseases.

It is technique where the commodity is left in the
field itself in a heap under shade for few days.
The outermost layer, which may be contaminated with soil, usually falls
away easily on curing. The dry under-layer should have an attractive
appearance. Onions are cured generally when they have lost 3 to 5% of
their weight. Generally, are dried in the field by stacking in a warm,
covered area with good ventilation.
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6. Curing
It is an effective operation to reduce water loss during
storage from hardy vegetables viz., onion, garlic, sweet
potato etc. In case of onion curing is a drying process
intended to dry off the necks and 2-3 outer scales of the
bulbs to prevent the loss of moisture and the attack by
decay during storage.
Contd….

However, in cool and moist climates, onions are cured with
artificial heat blown through a duct at 30oC. Onions can also be
cured by tying the tops of the bulbs in bunches and hanging
them on a horizontal support of pole, wire etc. pole in a well-ventilated
and shaded place. Curing in shade improves bulb
colour.
The essential conditions during curing are:
o Heat (~ 30oC)
o Good ventilation
o Low humidity
Contd….
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Irradiation is a treatment given to various fruits and vegetables to
control different postharvest diseases and disorders.
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7. Irradiation
Crop Control of Disease/disorder/pest Min. dose (kGy)
Apple Scald/ brown core 1.5
Apricot peach nectarine Brown rot 2
Banana Ripening inhibition 0.30-0.35
Lemon Penicillium rot 1.5 -2.0
Mushroom Inhibition of stem growth and cap
opening
2
Orange Penicillium rot 2
Papaya Disinfestation of fruit fly 0.25
Pear Ripening inhibition 2.5
Potato Inhibition of sprouting 0.08-0.15
Strawberry, grape Grey mould 2
Tomato Alternaria rot 3
But in most of the above cases, the technology of irradiation
finds a limited commercial application as either some cheaper and
more effective alternatives are available or the treatment leaves
undesirable effect on the produce and cause abnormal ripening.

8. Vapour heat treatment
This was developed to control infections of fruit flies in fruits.
The treatment consists of stacking the fruits in boxes in a
room which is heated and humidified by injection of steam.
The temperature and exposure time may be adjusted
depending upon the stage at which the fly is to be killed i.e. egg,
larvae, pupa or adult. The most difficult stage to control by VHT
is larval stage as the insect goes further into the fruit and away
from the surface thus requiring high temperatures for short time.
Generally the treatment of citrus, papaya, mango or pineapples
may be given at 43o C in saturated air for 8 hrs followed by
maintaining the temperature for further 6 hrs.
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Desapping of mango fruits is carried out in processing area by
trained workers under the supervision of processing supervisor.
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9. Desapping
Desapping is done by holding the mango fruits upside down
while cutting the stalk of fruits.
The stalks of mango fruits are cut very carefully to 0.5 to 1.0
cm by trained workers by using a scissor with sharp long
nose to avoid causing skin injury.
For exports, the pedicel of the fruits is cut approximately at a
length of 1 cm from the fruit with the help of sharp scissors and
fruits are kept up side down in special knitted pallets, for two
hours so that the latex flows out from the fruit completely. Care
should be taken that the latex drop does not fall on the fruit.

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