Back to > Major Fruits | Minor Fruits | Underutilized Fruits
Introduction
Name, Taxonomy, Botany
Nutritional Value
Common Varieties
Agronomy
Pest & Disease Management
Post-harvest & Processing
Market and International Trade
Research and Development
Harvesting: The avocado is unique in the way it ripens. It matures on the tree but does not ripen until it is picked. When the fruit on the tree begins to mature, it usually loses some of its “bloom” and changes color. Small, rusty brown specks may develop on some varieties and other fruit may become somewhat duller in appearance. Internally, the seed coat turns from ivory to dark brown upon maturity.
Fruit picked too early shrivels and lacks quality. The time of harvest depends upon the variety.
Variety
Season
Color
Anaheim
June – September
Green
Bacon
November – March
Green
Bonita
September – November
Green
Corona
June – August
Green
Daily
September – November
Green
Duke
September – November
Green
Dickinson
May – October
Dark purple
Edranol
April – July
Green
Fuerte
November – June
Green
Hass
April – October
Black
Hellen
June – September
Green
Jim
October – January
Green
Mac Arthur
July – October
Green
Mesa
May – July
Green
Nabal
June – September
Green
Pinkerton
December – April
Green
Reed
July – October
Green
Rincon
April – June
Green
Ryan
May – June
Green
Santana
September – February
Green
Zutano
October – March
Green
Note: The seasons indicated in the table are the approximate months of maturity. Seasonal, climatic effects and the district in which the tree is growing result in variation. Varieties not listed and seedlings vary greatly not only in fruitfulness, quality, and type but time of maturity as well.
Different varieties of avocados mature throughout the year, but each variety matures at approximately the same time of each year. Climatic factors may cause variations of 1 to 3 weeks. This characteristic has the advantage of holding the crop on the tree and making the time of harvest less critical. The storage life of fruit on the tree will vary from 2 months for Bacon to 8 months for Hass. Several pickings should be made to cover the range in fruit maturity. Avoid harvesting during wet weather as fruit are more susceptible to skin damage and fungal diseases.
Fruit of all cultivars must reach a minimum of 21% dry matter and ripen naturally without shrivelling before it can be harvested legally and sold. Fruit set can occur over a period of 4 to 6 weeks. Mature fruit has the following characteristics.
fruit stem becomes more yellow
when the fruit is cut and the seed is removed, the seed coat is dry and does not stick to the flesh, it is a dark brown colour
dark-skin varieties will show a change from green to purple
It also helps to know the usual time of maturity for the variety by taking a fruit sample and let it ripen indoors. If the fruit ripens within a reasonable time (7 to 10 days) without wilting, and shows all the desirable characteristics of the variety then start harvesting. Fruit is hand-harvested from trees when mature using an array of picking aids. Harvest the largest fruit at the first pick. On the larger orchards, trees are harvested with the aid of hydraulic ladders (cherry pickers) while on the smaller properties picking poles are used to reach fruit. For most cultivars, fruit needs to be clipped with a ‘button’ leaving a short 3mm corky stem attached to the fruit on the pedicle end. This reduces the risk of stem-end rot invading the fruit as it ripens. Don’t drop fruit as bruising will occur? Check fingernail length to avoid puncturing fruit. Fruit is picked into large bins usually mounted on trailers to facilitate their movement to the packing shed. It is important to keep the fruit out of direct sunlight after picking to prevent it from heating. Place harvested fruits in the shade.
Practically ‘Hass’ fruits are snapped from the tree ensuring that the flesh is not torn around the stem as a tear provides a site for infection. This is a much quicker practice provided fruits are treated within 24 hours with fungicide to prevent fungal infection.
Commercial standards require fruit to reach 8% oil content before harvesting. Mexican types ripen in 6 – 8 months from bloom while Guatemalan types usually take 12 – 18 months. Fruits may continue enlarging on the tree even after maturity. Purple cultivars should be permitted to color fully before harvest. Guatemalan types can be stored firm, at 4.5 – 10° C. for up to six weeks. Mexican types discolor quickly and require immediate consumption.
Here is the minimum percent dry matter standard that various avocado varieties must reach before they can be commercially harvested and sold to the public.
Dry Matter %
Varieties
17.7
Bacon
19.0
Furete
18.7
Zutano
21.6
Pinkerton
20.8
Hass
19.3
Jim
18.4
Susan
20.4
Rincon
24.2
Gwen
18.7
Reed
18.7
Clifton, Covacado, Duke,Henry, Select, Jalna, Leucadia, Santana, Teague, 287, other fall/winter varieties.
20.8
Anaheim, Benik, Bonita, Carlsbad, Dickinson, Edranol, Elsie, Ryan, Itzamna, MacArthur, Nabal, Queen, Thille, other spring/summer varieties.
Postharvest handling and packaging:
Postharvest treatment: The fruit is received, weighed, and unloaded from the trucks. It comes in boxes of different colors to identify its final destination: domestic market, export, and organic fruit. Then the fruit is cleaned with rotating brushes, and goes to the selection band. Within 24 hours of harvest, fruit is passed through a spray treatment of Sportak (prochloraz) to control anthracnose and stem-end rot. Fruit quality is determined by its freedom from insect, wind or hail marks. The selection is carried out manually or with the help of machines, and considering the shape, size, and sanitary characteristics of the fruit, as well as all the defects caused by insects, rodents, mechanical mishandling, and illness (viruses, bacteria and fungi). The selection criteria are also depends on the final destination of the fruit. Cooling the fruit following harvest is highly recommended to remove the field heat as much as possible.
Pre-cooling: A pre-cooling operation is generally carried out after packaging. Pre-cooling is of prime importance for the shelf life of avocado; it diminishes or slows the metabolic rate, ethylene synthesis and its action on the fruit, loss of texture, fungal infections, fruit ripening, and conditions the fruit for preservation at low-temperatures. Ideally, there should not be more than six hours from harvest to pre-cooling, and when this is not possible, the harvested fruit should not be allowed to reach an internal temperature higher than 26°C in the field and during its transportation to the packinghouse.
The quantity of the field heat is usually large, and cannot be eliminated fast enough in a regular refrigeration room. The freeze-blast method is the best suited for avocado pre-cooling. It is carried out until the temperature in the fruit reaches 6-7°C for “Fuerte” and “Hass”. The time that is required to achieve these temperatures varies according to the initial temperature of the fruit, temperature and velocity of the air, and the final temperature of the fruit.
However, it is important to end the pre-cooling process when the temperature of the fruit is 2°C above the ideal storage temperature. It is also of prime importance to assure that the storage temperature will not be lower than that established for the fruit, otherwise chilling injury can occur. The pre-cooling process lasts from 8 to 12 hours, with a relative humidity of 90 to 95% (Yahia, 2001).
Refrigeration: Temperature control during the post-harvest stage is the most important factor that helps maintain the quality and increase the shelf life of many fruits. Refrigeration is also useful to control illness and pests.Generally, the shelf life of avocado is inversely proportional to its respiration velocity.
It is of prime importance to avoid temperature fluctuations during transportation, because this can cause chilling injury, ripening, irregular softening, and rot (Yahia, 2001).
Storage of avocado: When avocado reaches the packinghouse, fruits of different batches are separated. The origin of the fruit, supplier, date, etc., should be registered. Before processing of the fruit, the lot shall be sampled in order to detect quarantine pests and diseases, and determine the general appearance of the fruit and its quality (stains, discolorations, injuries, mechanical damage, etc). At the same time, the characteristics of the particular variety are verified (Sánchez-Pérez, 2001).
The response of avocado to storage temperatures (Yahia, 2001) varies according to temperature ranges, as follows:
10 to 25°C: the fruit softens faster as storage temperature increases.
5 to 8°C: softening is controlled, and it will only occur if the fruit is transferred to higher temperatures.
0 to 4°C, softening at these temperatures is limited by time, due to the risk of chilling injury. However recommended storage conditions may vary according to the avocado variety (as shown in the table below)
Physiological disorders decrease when temperatures are kept at 7.5<°C at the beginning of storage, and then are lowered to 3.5°C, instead of maintaining 5.5°C the whole time.
Variety
%O2
%CO2
Temperature °C
Remarks
Hass
2-10
4-10
7
Storage time of 7-9 weeks
Lula, Booth 8, Fuchs
2
10
7.5
Increase shelf life twofold
Fuerte, Edranol, Hass
2
10
—
Reduces internal disorders
Non-specific
–
25
—
Reduces disorders and increases anthracnose
Fuerte
—
25
—
Delays maturation
Fuerte
2
10
5.5
Less dark spots in the pulp
Fuerte
—
25
5.5
Less dark spots in the pulp
Fuerte
3
0
24 h at 17°C
After this treatment, fruit can be stored at 2°C for 3 weeks
Booth 8, Lula
2
10
4-7
Storage time of 8 weeks
Fuerte, Anaheim
6
10
7
Storage time of 38 days
Waldin, Fuchs
2
10
7
Storage of 4 weeks, prevents anthracnose and chilling injury
Hass
2
5
—
Storage time of 60 days
Types of packaging: Fruit is then size and quality graded, packed into (trays and boxes as determined by the importing countries) and pre-cooled prior to transportation. The packaging material varies according to the market, being cardboard, plastic, or wood. The most common containers are single wall corrugated fiberboard or wooden boxes.
The first ones usually have a capacity of 4 kg with one level of fruit, while the second ones contain 10 kg, and the fruit is placed in bulk. The wooden box has a lower demand than the fiberboard box. Cardboard boxes have different perforation designs, and resistance to compression: from 269.1 to 1345.5 kg/m2, approximately (López-López, L. and Cajuste-Bontemps, J.F., 1999). Most fruit is shipped in refrigerated trucks by road to markets in major cities.
In Australia, for some interstate markets an Interstate Certification Agreement (ICA) is necessary; this requires an insecticide treatment. Many grading machines have a heated drying tunnel before the fruit is polished with brushes. Brushing removes visible spray residue and shines the fruit. Avocados are usually sorted into two quality grades and a processing line. Size counts range from 12 to 28 fruit per tray. Smaller fruit are bulk packed into 10kg cartons. Plastic inserts with moulded cups are placed in the tray. Single layer trays weigh around 6kg. Fruit are stamped with small stickers. These have brand names, variety identification and, for supermarkets, PLU (Price Look Up) numbers. A trade description must appear on one end of the package in letters 5mm high. It includes the name and address of the packer, the word ‘avocado’, variety, grade, count and or weight. It may also include a brand name, grower number,ICAand QA (Quality Assurance) particulars and date of packing. Packaging specifications for other countries are as the followings:
Storage and transportation: ‘Hass’ fruit are stored at 4 to 5 °C and other varieties at 6 to 8 °C.
Refrigerated transport is used from most growing areas. Controlled ripening of avocados using ethylene gas is usually done by the market agents.
Pre-ripening: Market research has shown that more avocados are sold if they are offered to the consumer in a ready-to-eat condition. This has led to a system of pre-ripening fruit prior to stocking retailer shelves. Fruit is gassed with ethylene at a central location and held at 21°C until it ripens, then taken to the retail point of sale.
Processed products:
Avocado is also used for the confection of baked products (such as cakes), to elaborate fine soup mixes, appetizers, and in the production of cosmetics (oils, skin lotions, soaps, shampoos, etc.) due to its oil content. Avocado oil is appreciated because it contains biodegradable and easy to absorb sterol. The oil is sent to theUnited States, where it is refined and then sent toJapanandEuropeas edible oil and cosmetic ingredient. Besides being an important cosmetic ingredient, the pharmaceutical industry considers the unsaponifiable fraction of the oil as a valuable raw material. From this fraction, the factor H is extracted, which is used in the pet food and cooking oil industries (SAGAR, 1999).
Types of products:
Frozen avocado – Original Chunky Avocado Pulp in 1, 2,& 6 lb. plastic pouches.
Avocado sauce- 100% Hass Avocado with minced onions and spices.
Southwestern guacamole – Feisty blend of chunky avocado, red bell pepper, onion, jalapeños and spices
Non-refined avocado oil – oil is extracted from selected Hass avocados by mechanical processes
Processing techniques
Avocado can be processed into avocado salsa, guacamole blend, avocado pulp, spicy guacamole, and avocado drinks.
Upon receiving the fruit, it is washed in a machine with rotating brushes and chlorinated water (200 ppm). Then its temperature is homogenized to 5°C to allow an even ripening. Avocados are stored for 3 days at 20°C at a relative humidity over 85%, adding 10 ppm of ethylene. Afterwards, the temperature is lowered again to 5°C and the fruit is kept at that point until processing (3 to 4 days). Since many clients prefer a chunky texture, the fruit must be ripe and firm.
Processing begins with a selection step, where the unsuitable fruit is discarded, the peduncle is removed, and the fruit is submerged in chlorinated water (200 ppm) for 10 min. Then it is cut, de-seeded, peeled and put into a mixer with other ingredients, such as onion, chili pepper, fruit concentrate, erythorbic acid (to promote color retention), and ascorbic acid. The resulting product is vacuum-packed and sealed into co-extruded five-layer bags, with a high barrier to oxygen. They usually pack in 6 pound bags, because most of their customers are restaurants, but they also have a 250 g package for retail marketing. The bags are frozen in a blast-freezer at -30<°C, and afterwards the bags are stored at -18°C).
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