Post Harvest Management: Avocado

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The avocado pear, belonging to the plant group Persea americana, is commonly known in Jamaica simply as “pears”. It is a native of the Tropical Americas, and flourishes in areas with over 15 cm (60 inches) of rain fall per annum, at between 55 and 550 metres elevation.

Varieties:

Most common varieties grown are:

Simmonds (in-season variety, i.e. ripening in the summer months, and Collinson, Lula (out-of season variety, i.e. ripening in December-February).

FRUIT STRUCTURE

The fruit is generally pear-shaped, and the edible part is a thick layer of greenish-yellow pulp. It is contained between the skin and the large seed.

NUTRITIONAL COMPOSITION (1 fruit, size 76.2 mm in diameter)

Water -284 grams (74%)

Food Energy -370 Cal.

Protein -5 grams

Fat -37* grams

Saturated fat - 7 grams

Oleic acid -17 grams

Linoleic acid -5 grams

Carbohydrate -13 grams

Calcium-22 mg

Iron-1.3 mg

Vitamin-630 IU

Riboflavin-0.43 mg

Niacin-3.5 mg

Ascorbic acid-30 mg

The avocado fruit is therefore a fat storing structure.

QUALITY REQUIREMENTS FOR EXPORT

Minimum requirements

The fruits must be clean, i.e. free from adhering soil and insects

Mature, i.e. not ripe or soft, but at the stage which will allow the fruits to ripen normally and arrive at the market with the desired degree of ripeness.

They must be of similar varietal characteristics, i.e. all fruits in any one lot must be of the same variety, must be similar in shape, texture, and skin colour.

Must be well trimmed, i.e. the stem ( pedicel) is cut off fairly smooth with not more than 6.4 mm beyond the shoulder of the fruit.

Grade requirement

Grade 1

Fruits should be well coloured, i.e. the colour characteristic of the variety.

Well formed, i.e. the fruit has the shape characteristic of the variety.

Free from damage, i.e. any defects that seriously affect the appearance, edibility, or shipping quality of the fruits; or the general appearance of

the avocadoes in the container, e.g. sunburn, scars, or bruises.

Size classification

Fruits should be classified by size according to the following definitions:

Uniformed in appearance, I.e. not more than 10% of packages shall contain fruits which show sufficient variation in size to detract from the appearance of the individual packages. The variation from the average length should not be greater than 3 mm.

Post-Harvest Treatment

Graded fruits should be wiped with a cloth containing 1% bleach solution, to remove debris and to disinfect the fruit. All insects such as mealy bugs or other, should be removed by use of a soft brush

A post harvest dip treatment in a solution of 0.1% Benlate (1 gm per litre) may assist in reducing fungal decay.

Packaging

Fruits should be placed in single layers in strong cardboard boxes with separators. Alternately, each fruit can be wrapped in tissue to improve presentation on the market and to reduce fruit to fruit rubbing.

Shredded paper placed in the base of the carton assists in reducing the level of damage during handling.

Field containers should be of 22 kg capacity and market containers no more than 12 kg capacity.

Do not use bags (fertilizer or crocus) to package these fruits, as this will lead to squeezing and squashing damage. Also bags are easily thrown and dropped, which will lead to damage of the fruits.

Field crates are preferable to bags for transport from the field to pack-house, or shed.

Do not leave packages exposed to the sun and wind. This will lead to the reduction of the storage/shelf life of the fruits.

Transportation

Packaged avocadoes should be placed separate from other types of fruits as they are sensitive to the ripening chemical, ethylene.

Stacking height of the boxes should be kept to a minimum of 8-10 boxes high in order to prevent compression damage

Storage

All West Indian cultivars are susceptible to chilling injury at low temperatures.

Best storage temperature is 12-13ºC and 85- 95% RH for green mature fruits resulting in a maximum storage period of two (2) weeks. At ambient temperature, storage life is reduced to 3-5 days.

POST HARVEST DISORDERS

  1. Chilling Injury

Common symptoms are a dark-brown or grey discolouration of the flesh, scalding and pitting of the skin. Fruit may not ripen properly on removal from storage.

  1. Anthracnone

This is a latent fungal infection caused by the organism colletotrichum gloeosporioedes. This is commonly found on maturing fruits. First sign of the disease is small light brown circular discolourations on the skin of the fruit.

As the fruit matures, the spots enlarge changing colour to dark brown or black with a sunken

appearance. The fungus enters the flesh and pink spore masses are seen.

  1. Stem-end rot

This disease is caused by dothiorella spp-a dark-brown to black rot develops at the stem

end of the ripening fruit as a firm dark brownring and proceeds to the other end of the fruit.

Remember

  1. That only good quality fruits will fetch a good price on the market.
  2. Consumers prefer to purchase green, mature avocadoes in order to obtain the best eating quality and some degree of storage/shelf life.
  3. Ripe avocados deteriorate rapidly at high temperatures and therefore exhibit a short shelf-life.
  4. Also the level of mechanical injury for avocadoes is high.

To obtain maximum profits from your crop, you must therefore ensure that:

Only sound, good quality fruits are placed on the market; Ripened fruits are placed in a different box or basket from green fruits.

Care must be taken in harvesting and; Fruits must be handled with care from the farm to the market place.

Low temperature management is essential to maintain good quality.

Remember that one of the important strategies of Fresh Produce Marketing is good customer relationship.

A good quality product will result in repetitive purchasing of goods from the dependable source.

HARVESTING

The fruit never ripens completely on the tree, but continues to enlarge in size.Fruit will only ripen after it is detached (harvested) from the tree.

MATURITY STAGE

Good quality fruit is obtained when harvesting is done at the proper stage of maturity.

Immature fruits will fail to ripen, shrivel rapidly, and also decay rapidly.

Most mature fruits are fairly large in size, with the skin colour becoming light green or yellowish green, and the surface sheen becomes dull in appearance. This condition is easily recognized by experienced farmers.

On a large farm, the oil content of the fruits is measured by chemical analysis to determine the minimum standard acceptable for the market. This level varies in different varies.

HARVESTING METHOD

Fruit should be harvested from the tree by a quick twist of the pedicel which will detach the mature fruits. The pedicel should then be clipped to prevent damage to other fruits.

Do not knock fruits off the tree. This will cause bruising and bursting of the fruit. Therefore fruits should be picked by using a pole or by hand.

The picking pole can be made of bamboo or some light wood provided with a cloth or crocus bag and a notch with an inner sharpened edge at the end. The bag is used to hold the fruit until the pick is brought to the ground and the fruit removed. Depending on the size of the bag, a maximum of three (3) limbs can be picked.

Hand-pickers standing on a ladder can also be used to harvest tall trees.

On a large farms, a platform mechanized system, elevating hand-pickers into the trees provide an efficient mode of harvesting.

POSTHARVEST ACTIVITIES

“Pears” are highly susceptible to the postharvest development of latent fungal infections, therefore extreme care must be taken in preventing damage to the fruits.

Do not throw or drop fruits in the field. Remember that damaged fruits must be separated from sound fruits if not, rapid spoilage will take place. Damaged fruits ripen much faster than sound fruits.