gopika,pre-cooling,sorting & grading

8/4/2019 Gopika,Pre-cooling,Sorting & Grading

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Wel Come


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PRE-COOLING, SORTING &GRADING OF FRUITS AND

VEGITABLES

Gopika M.HMK 810III B.Sc (Ag.maco)

Prepared by,


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PRE-COOLING: It is the rapid cooling process administered in commodities for

removal of field heat.

It has to be done immediately after harvest.

Pre-cooling reduces the rate of respiration of the freshly harvested

commodity accompanied by reduction in metabolic activity and

thereby extends the shelf life of the commodity.

Pre-cooling reducesField heat

Rate of respiration

Rate of ripening

Loss of moisture


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Pre-cooling method is selected based on

1. Nature of the product

2. Value and quantity of the product

3. Equipment and materials

4. Heat transfer characteristics of the product

Success of pre-cooling depends on

1. Time between Harvest and Pre-cooling.

2. Initial and final product temperature.

3. Accessibility of cooling medium and the produce.


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Types of Pre-cooling

1. Room cooling

2. Water cooling

3. Vacuum cooling

4. Forced air cooling


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Room Cooling:

This method simply involves placing the crop into a cold store.

This may be the same cold store where, the crop is to be stored for

long periods.

The type of room used may vary, but generally consists of a

refrigeration unit across which cold air is passed from fan.

The length of the time required is the only drawback in this method.


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Water cooling:

It can be done by flooding, Spraying or immersion.

Flood system is the most efficient, in which a film of cold water flows

rapidly and uniformly over the surface of warm substances.

The advantages of this method are Speed, Uniform cooling and no

weight loss or dehydration.


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Vacuum cooling:

Water in the product acts as refrigerant under low pressure

obtained in the vacuum chamber.

A pressure of 4.6mm of mercury reduces the boiling point ofwater from 100 0C - 0 0C.

As the water leaves the product in the form of vapour, The

product is cooled by supplying the latent heat required toevaporate water.


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Forced air cooling:

The simplest design is

achieved by building parallel

stacks of palletized cartons in a

refrigerated cold room.

The gap between the two

parallel rows of pallets is closed

off with a cover.

A small exhaust fan is placed at

one end. The exhaust fan removes

air from the enclosed space so

that the pressure falls.


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Sorting & Grading :

The main purpose of sorting & grading is to segregate produce into

grades A,B,C & culls .

Over ripe fruits or over mature vegetables, unpalatable for human

consumption may find use in animal feeding or in processing of

some products.

Sorting is done by hand to remove the fruits which are unsuitable

to market or storage due to damage by insects , diseases ormechanical injuries.

The remainder produce is separated into two or more grades on the

basis of the surface colour, shape or visible defects .

For example in an apple packing house in India 3 grades viz. Extra

fancy, Fancy &standard may be packed for marketing. The fourth

cull grade is meant for processing.


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cont.

In the Sorting of fruit & vegetables- sensory qualityattributes are taken in to consideration, such as presence

& extent of discoloration, blemish and shape.

While in Grading physical attributes which can be

measured such as size and weight are taken into account.

Often sorting precedes grading operations.


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Advantages of sorting and grading

It provides common language .

Reduce dispute of quality between seller and buyer.

Standardized grades form basis for price fixation & advertisement.

Improve marketing efficiency by selling a produce without a

personal selection.

Bargaining power is enhanced to get better premium for better

grades.

Grading the produce into certain size & shape facilitates packing &

transportation easy.

To eliminate re-sorting or re-packing at wholesale or transit markets.

Assist producers & other intermediaries in preparing fresh

horticultural commodities for market with appropriate labeling.


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Grading is done by hand or with the help of grading

machines. There are several mechanical graders

such are as fallows.1.Screen graders


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2.Weight graders


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3. Rotary barrel / Drum type

grader

4. Divergent roller type

Rotary barrel / Drum type grader

Divergent opening two stage


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5. Fixed opining roller type grader.

6.Expanding opening slot type grader.


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7.Computerized graders for size , weight and colour.


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SOURCE; A HANDBOOK ON POST HARVEST MANAGEMENT

OF FRUITS & VEGETABLES.

- By Dr. P. Jacob John.

HANDLING,PROCESSING, FERMENTATION & WASTE

MANAGEMENT. VOL-1 .

- By L. R. Verma & V. K. Joshi


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gopika,pre-cooling,sorting & grading

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