Avocado - Healthy Fruit

Botanical name: Persea americana
Plant family: Lauraceae
Other common names: butter fruit (India, China) avocado pear, alligator pear (English) due to its alligator skin texture and pear shape.

by Dr. Lalith Gunasekera

( June 14, Melbourne, Sri Lanka Guardian) Avocado plant originated in Mexico and has a long history of cultivation in Central and South American region. Avocados are commercially valuable and cultivated in tropical climates throughout the world, producing a green skinned, pear shaped fruit that ripens after harvesting. Avocados do well in mild winter areas of USA (California, Florida and Hawaii). Despite of range of varieties, avocados are divided into three main categories. These are Mexican, Guatemalan and West Indian types. Mexican types are native to dry subtropical plateaus and grow in a Mediterranean climate. Guatemalan types are native to cool, high altitude tropics and are hardier. West Indian varieties thrive in humid, tropical climates. Hybrid types exist among all three forms.

Avocado trees need well aerated soils, ideally more than 1 m deep. Yield is reduced when the irrigation water is highly saline. The soil and climatic conditions are available only in a few areas of the world, particularly in Southern Spain, South Africa, Peru, Chile, Vietnam, Indonesia, Parts of Southern India, Sri Lanka, Australia, New Zealand, Philippines, Malaysia, Central America, Caribbean, Mexico, California, Arizona, New Mexico, Texas, Florida and Ecuador. Each region has different types of cultivars.

Avocado is one of the popular fruit crops in Sri Lanka. It is commonly grown in home gardens of the wet zone of the country. The first introduction of avocado into Sri Lanka is not well documented but some evidence suggests that it could have been originally introduced during the Dutch occupation, over 200 years ago.

The avocado was introduced from Mexico to the US state of California in the 19th century and has become an extremely successful cash crop. About 24,000 hectares is located in Southern California. Internationally avocado exports are dominated by Mexico. 

The avocado first officially found its way to Australia in seed form in 1840 and was planted in the Botanical Gardens in Sydney. Today some hundreds of year later avocado orchards can be found throughout Queensland, New South Wales, South Australia, Western Australia, Victoria and Tasmania. 

Avocado is a dense, evergreen tree, shedding many leaves in early spring. The tree grows up to 20 m with alternatively arranged leaves, 12 – 25 cm long. Leaves are glossy, elliptic and dark green with paler veins. They normally remain on the tree for 2-3 years. 

The flowers are greenish-yellow, 5 -10 mm wide. Avocado flowers carry both male and female reproductive organs. Each flower opens twice over a two day period. Flowering normally lasts for 3 – 4 weeks, longer in cooler growing areas. Trees are partially self pollinating and often propagated through grafting to maintain a predictable quality and quantity of the fruit. The pear shaped fruit is 7 -20 cm long, weighs between 100 – 1000 g, and has a large central seed, 5-6.4 cm long. The avocado is unique in the way it ripens. It matures on the tree but does not ripen until it is picked. This characteristic has the advantage of holding the crop on the tree and making the time of harvest less critical. Fruit picked too early shrivels and lacks quality. An average avocado tree produces about 150 – 500 avocados annually. The avocado tree does not tolerate freezing temperatures and can be grown in subtropical or tropical climates.

Avocado propagated by seed can bear fruit, it takes roughly 4-6 years to do so and the offspring (new plants) is unlikely to resemble the parent cultivar in fruit quality. Avocado plants are vulnerable to bacterial, viral, fungal and nutritional diseases. Disease can affect all parts of the plant, causing spotting, rotting, pitting and discoloration.

The main varieties grown in the world are Hass, Fuerte, Reed, Sharwill, Shepard with the most dominating being Hass which accounts for 75% of the Australian market. Hass produces fruit year round and accounts for 80% of cultivated avocados in the world. Hass trees have medium sized, ovate fruit with black, pebbled skin. The flesh has a nutty, rich flavour with 19% oil. All Hass avocado trees are descended from a single “mother tree” raised by a mail carrier named Rudolph Hass of California. 

A few individual avocado seedling trees growing in backyards are estimated to be about 100 years old. In spite of the long life of a few avocado trees, there are a number of causes that shorten the useful life of avocado orchards. Care must be taken to prevent from pest and diseases which can be harmful for avocado growth and development. Avocados are extremely susceptible to the roo rot fungus. No avocado rootstock is completely resistant to this disease. 

The knowledge of the average consumer with regards to the nutritional value of avocado is still very poor. Until recently, the avocado was consumed with caution as the level of fat in fruits created some kind of misconception among the people that it was unhealthy to consume. However, with the propaganda launched by the horticultural industries and health organisations regarding its nutritional value and its ability to control heart diseases a better awareness was created among people.

Uses

The avocado is one of the most valuable foods nature has given man. For those who concerned about eliminating meat from their diet, this offers not merely a substitute but a food which is much superior in value for human maintenance.

• The avocado fruit of horticultural cultivars does have a markedly higher fat content than most other fruits. Most of the fat in avocados is monounsaturated fat, which is considered healthy in the human diet. A whole medium avocado contains approximately 25 % of the recommended daily amount of saturated fat. Avocado also have 60% more potassium than bananas. They are also rich in B vitamins as well as vitamin E and K. They contain no cholesterol.

• Avocado is very popular in vegetarian cuisine, as substitute for meats in sandwiches and salads because of its high fat content. In Australia, it is commonly served in sandwiches, on toast or with chicken. 

• In Sri Lanka, avocados are made into juice by mixing with sugar, milk or water served with vanilla ice cream.

Avocado Juice

NUTRITIVE VALUE – AVOCADO RAW (EDIBLE PARTS) – PER 100G

Energy - 160 kcal
Carbohydrates - 8.53 g
Sugars - 0.66 g
Fiber - 6.7 g
Total Fat - 14.66 g
Saturated - 2.13 g
Monounsaturated - 9.80 g
Protein - 2 g
Calcium - 12 mg
Iron - 0.55 mg
Magnesium - 29 mg
Phosphorus - 52 mg
Potassium - 485 mg
Sodium - 7 mg
Zinc - 0.64 mg
Copper - 0.19 mg
Manganese - 0.14 mg
Vitamin B1 - 0.067 mg
Vitamin B2 - 0.130
Vitamin B3 - 1.73 mg
Vitamin B6 - 0.257
Vitamin C - 10 mg
Vitamin A - micro g 146
Vitamin E - micro g 2.07

(Source: USDA Nutrient database)

• Avocado flesh is an excellent source of minerals such as iron, copper, manganese and magnesium. It contains more potassium than bananas. 

• Avocados have the highest protein content of any fruit.

• We tend to think about carotenoids as most concentrated in bright orange or red vegetables like carrots or tomatoes. While these vegetables are fantastic sources of carotenoids, avocado-despite its dark green skin and largely greenish inner pulp - is now known to contain a spectacular array of carotenoids. Researchers believe that avocado's amazing carotenoid diversity is a key factor in the anti-inflammatory properties of this vegetable. The list of carotenoids found in avocado include well-known carotenoids like beta-carotene, alpha-carotene and lutein, but also many lesser known carotenoids including neochrome, neoxanthin, chrysanthemaxanthin, beta-cryptoxanthin, zeaxanthin, and violaxanthin.

• Avocado is an alkalinizing food (the mineral end products of metabolism have an alkalinizing effect in the blood and other bodily fluids). The human body works to maintain a slightly alkaline pH, an alkalinizing diet is the most healthful way of eating. Meat, dairy and most raw nuts create acidity in the body. 

• Avocados are very good source of soluble and insoluble dietary fibre. 100 g of fruit provides 6.7 g or about 18% of recommended daily intake. Dietary fibres help lower blood cholesterol levels. 

• Avocados are also used in high quality cooking oils and in the manufacture of cosmetics. The Australian consumption of avocado is around 1.6 kg per capita, well below the Mexican level of 10 kg per capita.