History, Description and Uses of Cashew
Cashew, (Anacardium occidentale), evergreen shrub or tree of the sumac family (Anacardiaceae), cultivated for its characteristically curved edible seeds, which are commonly called cashew “nuts” though they are not true nuts. The domesticated cashew tree is native to the New World but commercially cultivated mainly in Brazil and India.
The cashew tree (Anacardium occidentale L.) is a medium-sized tropical tree usually cultivated for its fruit (cashew nut) and pseudofruit (cashew apple). It is also a multipurpose species that provides a broad range of services. About 30-40% cashew kernels are discarded during the process of roasting and are then fed to livestock.
The seeds, rich in oil and distinctively flavoured, are commonly used in South and Southeast Asian cuisine and are a characteristic ingredient of numerous chicken and vegetarian dishes of southern India. In Western countries they are eaten mainly as a premium-quality protein-rich snack food.
Description of Cashew
Cashew nuts are actually seeds that adhere to the bottom of the cashew apple, the fruit of the cashew tree, which is native to the coastal areas of northeastern Brazil.
Cashew apples, while not known in the U.S., are regarded as delicacies in Brazil and the Carribean. The seed we know as the kidney-shaped cashew “nut” is delicate in flavor and firm, but slightly spongy, in texture.
You have probably noticed that cashews in the shell are not available in stores. This is because these nuts are always sold pre-shelled since the interior of their shells contains a caustic resin, known as cashew balm, which must be carefully removed before they are fit for consumption. This caustic resin is actually used in industry to make varnishes and insecticides.
Cashews, known scientifically as Anacardium occidentale, belong to the same family as the mango and pistachio nut.
History of Cashew
The cashew tree is native to northeastern coastal areas of Brazil. In the 16th century, Portuguese explorers took cashew trees from this South American country and introduced them into other tropical regions such as India and some African countries, where they are now also cultivated.
The cashew tree has always been a prized resource owing to its precious wood, cashew balm and cashew apple, but the cashew nut itself did not gain popularity until the beginning of the 20th century.
The tree produces wood that is useful in local economies for such practical items as shipping crates, boats, and charcoal as well as for a gum that is similar to gum arabic. The resin within the shells of the fruit is used as an insecticide and in the production of plastics; it also is important in traditional medicines.
The cashew apple is used locally in beverages, jams, and jellies, though most cultivation is directed toward production of the valuable seed crop. Parts of the cashew must be handled with care by susceptible individuals because it is related to poison ivy and poison sumac and can cause an allergic reaction in some people.
Today, the leading commercial producers of cashews are India, Brazil, Mozambique, Tanzania and Nigeria.
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Uses of Cashew
The cashew tree is a multipurpose species, and cashew products have a wide range of uses. The kernel of the cashew nut, the pseudofruit (cashew apple) and the leaves are edible. Almost all parts of the cashew tree are reported to have ethnomedicinal properties.
Cashew nuts (kernels) must be extracted from their poisonous shell with caution in order not to be contaminated by the toxic substances embedded in the mesocarp. Once extracted from the nut, the kernels are roasted to destroy the remaining toxins. The kernels are a nutritious food as they contain large amounts of fats, protein, carbohydrates, vitamins and minerals.
Discarded cashew nuts are nuts unfit for human consumption. In the literature they are often referred to as cashew nut meal or cashew nut reject meal. They are used to feed livestock.
Cashew apples (pseudofruit) are too fragile to be suitable for transport and relished only in areas of production, such as Brazil, Mozambique and Indonesia. They can be eaten fresh in salads, pressed to make juices, cooked in syrup or made into jams to preserve them.
Cashew pulp is the residue of the separation of the nut from the pseudofruit, and cashew bagasse (cashew pomace, cashew apple waste) is the residue of the juice extraction from the pseudofruit. Both products are suitable for livestock feeding. It should be noted that the term “cashew pulp” is ambiguous and sometimes used for the bagasse.
Cashew nut oil meal, or cashew nut oil cake, is the residue of the oil extraction from kernels. It is suitable for livestock feeding.
Cashew nut testa are the red skins that are manually or mechanically removed in the final step of preparing cashew nuts for confectionery. These skins may contain pieces of broken kernels and can be used as feed.
Cashew tree leaves can be cut and eaten fresh or cooked.
Cashew tree timber provides good firewood and can make valuable charcoal. The nut shells can be burnt to produce heat to be used in the processing of Cashew Nut Shell Liquid.
Cashew Nut Shell Liquid (CNSL), also known as cashew shell oil, is contained in the fruit mesocarp. It is a mixture of 70% anacardic acid (a salicylic acid analog, and a strong skin irritant) with 18% cardol, and 5% cardanol.
The two latter components are caustic phenolic substances that readily polymerize and are used for epoxy resins, varnishes, and many high-tech materials that can withstand high temperatures, such as brake linings. CNSL is also used as a pesticide against termites in timber, and the bark gum is repellent to insects.
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The plant may grow to 12 metres (40 feet) in height where the soil is fertile and the humidity high. The leathery leaves are spirally arranged and elliptical in shape. The curved fruit, which is not a true nut, is shaped like a large thick bean and can reach more than 2.5 cm (1 inch) long.
It appears as though one of its ends has been forcibly sunk into a pear-shaped swollen stem (hypocarp), called the cashew apple. The cashew apple, which is an accessory fruit (e.g., not a true fruit), is about three times as large as the true fruit and is reddish or yellow. The true fruit has two walls, or shells.
The outer shell is smooth, thin, and somewhat elastic and is olive green until maturity, when it becomes pale brown. The inner shell is harder and must be cracked like the shells of nuts to obtain the edible seed inside. A brown oily resin is produced between the two shells and can blister human skin.
The cashew apples are picked by hand, and the curved fruits are first detached and then sun-dried. In some localities the dried fruits are roasted amid burning logs, where the heat causes the outer shells to burst open and release the caustic resin.
The resin quickly catches fire, giving off fumes that can be injurious to the eyes and skin. In improved methods of roasting, the poisonous properties are dispelled in roasting cylinders. Later the inner shells are broken open by hand and the kernels heated to remove the seed coat.
Read Also: Health Benefits of Cashew Nuts
Gneneral Culture of Cashew
1) Soils and Climate
Tolerant of sandy, poor soils, Soil pH 4.5-6.5, intolerant of poor soil drainage.
Drought tolerant if soils are deep, and can grow in areas receiving only 30-50″ of rain per year
High rainfall and humidity favor diseases that destroy the flowers and reduce fruit set. No cold tolerance
2) Propagation
Propagation is most often by seed, planted directly in the field where the tree is to be sited.
Rootstocks – generally none, but cashew seedlings can be used for rootstocks for grafted trees.
3) Planting Design, Training, Pruning
Planting Design: 20-35 ft between trees and rows. Cashews form open, spreading canopies naturally, and very little information on pruning exists.
Cashew Harvest and PostHarvest Handling
1) Maturity
The cashew apple and nut abscise from trees naturally when ripe. Maturation occurs over a period of several weeks during the dry season.
2) Harvest Method
Nuts are collected from the ground by hand. Frequent passes though the planting must be made if apples are to be utilized, as they are highly perishable. Rain at harvest may increase rot and stimulate nut germination.
3) Postharvest Handling
The presence of caustic cashew nut shell liquid (CNSL) in the shells makes cashew processing more difficult and hazardous than for other nut crops. After harvest, the nuts are dried in the sun or in simple tray driers and stored for processing later.
Dried nuts can be stored for about 2 years at room temperature after reaching water contents of 5-10%. Nuts are re-hydrated partially by soaking or storing in high humidity since this facilitates extraction of whole kernels and CNSL.
Nuts are separated by size before roasting to ensure uniformity of the roasting process. After roasting, nuts are shelled either by hand or in machines.
4) Storage
Vacuum packed, roasted nuts can be stored for up to one year, and carbon dioxide packing extends life an additional year.
Read Also: Complete Guide on How to Grow and Care for Mango
The Cashew’s Contibution to Diet
The cashew apple may be consumed fresh, but contains high quantities of tannins yielding a bitter taste and dry mouth feel. It is more often cooked, partially dried, or candied, as in the Dominican Republic and India.
The alcoholic drink, Feni, is made from fermented cashew apple juice in India. The wine made from the juice is said to be the finest made from tropical fruits. Per capita consumption of cashew is 0.8 lbs/year in the USA.
Dietary value, per 100 gram edible portion:
| Cashew nut | Cashew apple | |
| Water (%) | 3-7 | 86 |
| Calories | 578 | — |
| Protein (%) | 18-22 | 0.1 |
| Fat (%) | 46 | 0.3 |
| Carbohydrates (%) | 27 | 9-15 |
| Crude Fiber (%) | 1.1 | 0.75 |
| % of US RDA* | ||
| Vitamin A | 0 | 0 |
| Thiamin, B1 | 45 | — |
| Riboflavin, B2 | 12 | — |
| Niacin | 12 | — |
| Vitamin C | 0 | 200-600 |
| Calcium | 0.2 | 0.5 |
| Phosphorus | 5.8 | 2 |
| Iron | 50 | 5 |
| Sodium | 4.6 | <0.1 |
| Potassium | 12 | 0.1 |
* Percent of recommended daily allowance set by FDA, assuming a 154 lb male adult, 2700 calories per day.
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