Steps involved in Cashew Processing: An Overview

Cashew processing involves various steps that transform the raw cashew nut into a finished product. This process includes cleaning, roasting, shelling, drying, peeling, grading, conditioning and packaging. The cleaning step removes any foreign material or debris that may be present in the cashew nuts. Roasting is essential to impart flavor and aroma to the nuts, while reducing their moisture content. Shelling removes the outer hard shell and drying reduces the moisture content further. Peeling involves removing the thin inner skin or testa from the kernel. Grading involves sorting the nuts based on their size and quality. Conditioning involves maintaining moisture content at a desired level. Finally, the cashews are packaged and stored appropriately to preserve their quality. Cashew nut processing has undergone significant advancements in recent years to improve efficiency as well as enhance the quality of the final product.

Read: November Issue of Food Infotech Magazine.

Cashew (Anacardium occidentale L.) is native to Eastern Brazil and is an important tropical cash crop. Five centuries ago, Portuguese travellers introduced it in India. It was spread mainly by elephants that ate the fruit and left the seed because it is too hard to digest. During 2013-14, the global cashew production from an area of 5.31 million hectares was nearly 2.67 million tons (Cashew Handbook, 2014), and half of the contributions had come from Asian countries. India is the fourth largest producer of cashew nuts, next to Vietnam, Nigeria and Ivory Coast. In India, It is grown along the coastal regions of Maharashtra, Goa, Karnataka and Kerala on the West Coast and Tamil Nadu, Andhra Pradesh, Odisha and West Bengal on the East Coast.

Processing of Cashew Nuts

Processing of cashew refers to the post-harvest process that helps to extract the edible part (Kernel) from the raw seed. It can be done by both mechanical and manual methods. In India, it can be done mostly by manual method. It involves several processes like cleaning, roasting, shelling, drying, peeling, grading, conditioning and packaging. (Bhaskara Rao et al., 1993)

Cleaning

Cashews are collected from different farms. So the chance of foreign matter in the cashew is very high, which will greatly impact the final process. So the dust and other foreign matter should be cleaned from the cashew before going for further processes.

Roasting

Roasting is the application of heat in the nut to release the Cashew Nut Shell Liquid (CNSL) that helps easily extract cashew kernels from the shells during shelling (Azam-Ali et al., 2001). Roasting can be done by three methods (Balasubramanian., 2000). They are as under:
1) Drum Roasting
2) Oil Bath Roasting
3) Steam Roasting

Drum Roasting

An open pan roaster is improved and developed into a drum roaster, one of the oldest widely-used methods. The rotating drum is tilted and will be heated initially and to an extent. The drum is tilted from the fire to prevent the excess burning of nuts. The nuts are ignited and the liquid in the shells of cashew nuts gets burnt. The drum is rotated for 3-5 minutes, and it is rotated mostly by hand (Saraoj, P. L. et al. 2015). Roasted nuts will be collected at the lower end of the drum. After roasting, the nuts will be collected and covered with ash to remove the excess oil content in the shell.

Oil Bath Roasting

This is an outdated method in India, where the conditioned nuts are passed through a rectangular vessel 2-3 feet wide and 3 feet deep (Saraoj, P. L., et al. 2015) bath of CNSL at the temperature of 170°-200°C. Cashew shells will be used as fuel for the furnace. The nuts will be conveyed with the help of a screw conveyor and belt conveyor.

Steam Roasting

The raw nuts are steam cooked at 5.6-7.0 Kg/Cm² for 20-25 minutes (Saraoj, P. L. et al. 2015). Then the conditioned nuts will be shelled using hand or leg-operated shelling machines. This type of roasting is used on a large scale. This method helps in the easy removal of shells.

Shelling

Shelling or Decortication is the process of removal of shells from the nuts to produce whole and clean kernels. Shelling can be done by both mechanical and manual methods. In India, shelling is mostly done by manual methods.

Manual Shelling

Manual shelling involves the removal of shells by using a mallet or a light hammer. The nuts will be knocked 3-4 times so that the kernel can be obtained without breaking. The expected outturn is 90%. The output range is 15-20kg per 8hr of a day (Saraoj, P. L. et al. 2015). The main disadvantage of this method is this method of shelling requires skilled labour.

Mechanical Shelling

Mechanical shelling involves removing shells using a foot-operated shell cutter, mainly used commercially. It consists of a pair of blades. The nut is inserted in between the blades. The clearance between the blade is adjusted according to the nut size. Using the lever, the outer shell of the nut is broken, and the kernel is removed using a sharp needle. The main challenge in mechanical shelling is the removal of kernels without breakage. Around 14-22 kg of nuts can be obtained in 8 hours (Karthik C et al., 2020). The main disadvantage of this method is the high chance of contamination and the requirement of skilled labor.

Drying

After shelling, the kernels should be dried to bring down the moisture content. Drying can be done either mechanically or by using non-conventional energy sources. Borma driers are the most commonly used driers. Air will be heated indirectly from the furnace and sent through the mesh by a blower. Cashew shells will be used as fuel for the furnace. The temperature ranges from 70-100°C. The moisture of the kernel after drying should be 2-4% (d.b).

Peeling

The peeling process involves removing adhering testa from the kernel after drying. After drying, the kernels should be cooled for 24-48 hours (Saraoj, P. L. et al. 2015). Peeling can be done by gentle removal by using fingers or scraping with the help of bamboo sticks and stainless steel blades. Nuts with testa will be considered low quality. So the testa will be cleaned properly.

Grading

The roasted, shelled, dried, and peeled nuts will be graded according to size. Grading is mainly done for export purposes. Grading of cashew is done under the Govt. of India specifications under the Export (quality control and Inspection) Act 1963. Twenty-three different export grades of kernels have been recognized under the act. W-210 (440–460/kg) is the grade of the largest kernels, and W-500 (1000–1100/kg) is the grade of the smallest kernels. (Gopinathan Nair., 2002)

Conditioning

Conditioning is an important step in cashew nut processing. Conditioning should be done before packaging cashew. If the cashew is sealed in metal cans and the moisture is more than 5%, microbes will easily grow in the nuts.

Packaging

Cashew nuts tend to rancidity. So it should be packed so that the permeability of oxygen and moisture is low. It will be packed under a vacuum or completely filled with inert gases on a larger scale. Carbon dioxide or Nitrogen is used for filling. The filling can be done with the help of a VITAPACK machine and the packs will be sealed. After packaging, the nuts will go for HACCP analysis to ensure the export conditions.

Conclusion

Cashew processing involves several stages, each requiring specific skills and equipment to produce high-quality cashew nuts. Despite the challenges, the demand for cashews continues to grow globally and cashew processing can be a profitable business venture, particularly in developing countries. However, it requires significant infrastructure, equipment and skilled labour investment. The industry is poised for growth as consumers become more health-conscious and the demand for organic and natural products increases. As a result, cashew processing businesses that continue to innovate and adapt to changing market trends and consumer preferences are likely to succeed. Overall, the cashew processing industry has a promising future and it remains a vital source of income for many people.

References:

1. Bhaskara Rao, E. V. V., Swamy, K. R. M., Yadukumar, N., & Dixit, S. (1993). Cashew Production Technology PP 36.

2. Azam-Ali, S. H., & Judge, E. C. (2001). Small-scale cashew nut processing. Coventry (UK): ITDG Schumacher Centre for Technology and Development Bourton on Dunsmore, 1-70.

3. Balasubramanian, P. P. (2000). Cashew—the premier crop of Indian commerce. In State Level Seminar on Cashew-Selected Articles on Cashew (pp. 3-11).

4. Saraoj, P. L. (2015). Advances in Cashew Production Technology. ICAR – Directorate Of Cashew Research, Puttur, Karnataka, 117-121.

5. Karthik, C. S., Pariari, A., Bhutia, K. C., & Bhutia, S. O. (2020). Processing Methodologies for Few Plantation Crops in India (Arecanut, Betelvine, Cashew, Cocoa and Oil Palm). Innovations in Food Technology: Current Perspectives and Future Goals, 29-39.

6. Gopinathan Nair K (2002) Indian cashew industry. Directorte of Cashew Nut and Cocoa Development, Kochi, pp 142-146.

About the Authors:
1. Saran V.
NIFTEM – Thanjavur,
Tamil Nadu, India.

2. Dr. N. Venkatachalapathy
NIFTEM – Thanjavur,
Tamil Nadu, India.
Email ID: venkat@iifpt.edu.in