A process for extracting cashew nut shell oil has been developed at Laurenco Marques, Portuguese Africa by Sociedade Imperial De Caju E Oleos LDA, a Portuguese body corporate and has been patented in India in September 1961 (Indian Patent 78612, September 25, 1961)15. The invention disclosed in the above patent relates to an improved unitary continuous industrial method for extraction of shell oil from cashew nuts which is valuable from industrial and therapeutic point of view and for separation of cashew kernels having exquisite flavour and vitamin content without any contamination by the oil (which is acrid and produces painful inflammation of the skin) and untarnished by treatment. This method is claimed to have greater advantages in respect of producing quality products at cheaper rates and higher production levels than the primitive extraction methods which entailed more labour, higher costs and lower output.

Steps Involved in Manufacturing

• Wetting of the cashew nuts by dipping in a hot water vat at 20-25°C to strike a moisture balance between the shell and kernel of the cashew nut and removal of superficial moisture from the nuts and then steaming of the nuts to open up the pores of the shells,
• Subjecting the conditioned nuts dipping in a vat containing cashew nut shell oil where temperature is kept at 170°C to 185°C or preferably at 180°C, for a predetermined period when most of the oil issues out of the shells,
• Vibrating the nuts discharged from the oil bath and subsequent centrifugation in order to remove the adhered oil,
• Incision of the shell walls of the nuts and centrifugation of the seed against a breaking wall,
• Separation of the kernel from the cracked cashew shells and peeling of the skin by heating with hot air and mechanical rubbing of the kernel and effecting the removal of the peel under the action of an air stream; and
• Classifying the peeled nuts and subsequent packing under inert gas in tightly closed containers.