RAW CASHEW NUT PROCESSING

Cashew nut processing allows for the development of an important by-product, which can increase its added value. The liquid inside the shell (CNSL) represents 15 percent of the gross weight and has some attractive possible medicinal and industrial uses. CNSL is one of the few natural resins that is highly heat resistant and is used in braking systems and in paint manufacture. It contains a compound known as anacardium , which is used to treat dermatological disorders. The main markets for CNSL are the United States, the European Union (mainly the United Kingdom), Japan and the Republic of Korea. Together these account for over ninety percent of world trade, most of which is supplied by India and Brazil.

Cashew (Anacardium occidentale L.) a native of Eastern Brazil introduced to India just as other commercial crops like Rubber, Coffee, Tea etc. by the Portuguese nearly five centuries back. The first introduction of cashew in India was made in Goa from where it spread to other parts of the country. In the beginning it was mainly considered as a crop for afforestation and soil binding to check erosions. The nuts, apple and other by products of this crop are of commercial importance. Though its commercial exploitation began from the early 60’s, marginal lands and denuded forests were the areas set apart for the plantation development. Due to the absence of high yielding varieties and multiplication techniques, indiscript seeds and seedlings were used for planting purposes. Because of its adaptive ability in wide range of agro climatic conditions it has become a crop of high economy and attained the status of an export oriented commodity bringing considerable foreign exchange to the country.

Cashew (botanical name Anacardium occidental) was introduced in India by the Portuguese four centuries ago, mainly to prevent soil erosion. Cashew ranks second among the nine tree nuts which figure prominently in international trade circles, first being almond. The cashew adapts to various types of soils and climatic conditions and is hardy and draught resistant tree.

For several centuries the cashew trees was considered merely as a sturdy perennial tree which yielded soft wood and bore the delicious juicy cashew apple. The peculiarity of the cashew apple is that it has nut outside. In the earlier days, the nut was thrown away after the apple was eaten. The nut was rejected since it has a hard shell cover which contains a corrosive liquid (cashewnut shell liquid) which burns the skin on contact. As time passed, interest developed in the nut and various methods of extracting the kernel from the nut proved successful.

Cashew nut has been cultivated in several countries for a long time but the credit for launching into commercial production and export of cashew kernels goes to India.

Cashewnut Shell Liquid

Cashew nut shell liquid (CNSL) is a bye product of the cashew industry in India, which is a major earner of foreign exchange. It is contained in the soft honey comb structure between the outer shell and the kernel of the cashew nut. The cashew nut tree (Ana cardium Occidentale Linm, Hindi, Kaju) belongs to the natural order Anacardiaceae, even as Bhilawan tree and grows at altitudes below 1000 ft along the west and Eastern coasts of India. It is extensively cultivated in Brazil East Africa, Tanzania, Mozambiques Madagascar, Philippines and other tropical regions.

The cashew fruit has a kidney-shaped nut 1 to 1.5 inches long. The nut is attached to the end of fleshy receptable or enlarged or rhomboid-to-oval having 2-4 1/2″ length and is bright yellow to red with a waxy skin. Pericarp of the nut consists of a coriaceous epicarp, spongy mesocarp and story endocarp. The mesocarp consists of a honey-comp net work of cells which gives cashew nut shell liquid.

Cashew Testa

Cashew testa is the outer skin of cashew kernel which contains about 25% of tannin material and 11% of non tannins. The tannins consist of D-catechin, gallic acid and leuco-cyanidin, significant tannin procursor, while the non-tannins consist of quinic and caffeic acids. These tanning materials have shown similar properties to that of imported wattlebark tannin used in leather industry. The latter is being imported from East African countries to the extent of 12-15 thousand tons per annum costing nearly 2 crores. The availability of cashew testa is estimated around 2000-2500 tons per year in Quiling region alone where 75% of the factories process cashew nuts. Recently a tannin extraction plant of the Kerala State Development corporation Ltd., has been started at Kottiyam about 8 k.m. from Quilon. The corporation with its 34 cashew processing factories, is the first to start a bye product plant of this nature. It is considered to be the biggest unit in the cashew industry, accounting for more than one fourth of the total processing capacity in the state of Kerala. It is estimated however that 3-4 thousand tons of cashew tesa would be available within the country and from which 500-600 tons of cashew tannin extract costing about 10 lakhs of rupees could be made. The residue of the tannin which is not soluble in water but soluble in mild alkalies. The extracts may find use in oil drilling mud and in the “Boiler compounds” generally used in railway steam boilers.

Cashew Kernel

The cashew Kernel covered with testa is contained in a shell 1/8″ thick is contained in a shell 1/8″ thick which forms about 67 percent of the whole cashew nut, the remainder being the kernel. Cashew kernel yields about 42.2% of a glyceride oil of the following fatty acid composition.

Oleic Acid 59.6%
Linoleic Acid 19.62%
Palmitoleic Acid 11.14%
Palmitic Acid 0.89%
Stearic Acid 8.75%

The composition of the cashew kernel is very similar to that of sweet almond and constitutes a very nutritive and concentrated food. The kernel contains larger percentage of protein (20 percent) and is rich in calcium, phosphorus, iron and Vitamin A, Vitamins B1 and B2 are also present to a small extent. Recently cashew nut neutral lipids glycolipids and phospholipids were isolated by silic acid chromatography. Each lipid class has characteristic fatty acid distributions with phospholipids being higher in linoleic acids.