Drying Characteristics and Nutritive Analysis of Coffee Beans under Different Drying Methods

Ayuni Nasrin Binti Mohd Sukiri; Adeline Shu Ting Tan; Chi Huey Ng; Arham Abdullah; Wan Ahmad Amir Zal Wan Ismail; Jidon Janaun.

Transactions on Science and Technology, 8(3-3), 439 - 444.

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Heating is a post-harvest treatment for palm fruitlets that halts enzymatic activities that causes the rise of free fatty acid (FFA) in palm oil-related end-products and prevent deterioration of materials due to microbial contamination. Microwave heating has been extensively utilized for this process. However, due to limited access to electricity in rural areas, solar drying is proposed as an alternate method to perform the process. A proven solar drying system (UMS Eco-Solar Dryer) developed by Universiti Malaysia Sabah was used to perform the drying of palm fruitlet. This study focused on identifying the drying characteristics of palm fruitlet upon reaching its equilibrium moisture content (EMC) in an indirect type solar dryer under natural convection. Cumulative moisture loss of 17.05% was identified at EMC in 168 hours. An experimental drying curve of the drying process was established at the temperature range of 32.6 to 50.5 °C. The average air velocity measured at the drying chamber inlet was 0.26 m/s. Four mathematical models were used to describe the drying curve. Quadratic and logarithm equations are the best model to describe the constant rate period and falling rate period respectively.

KEYWORDS: Solar dryer; indirect; natural convection; palm fruitlet drying; drying characteristics

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  1. Belitz, H., Grosch, W. & Schieberle, P. 2009. Food Chemistry (4th edition). Berlin Heidelberg: Springer-Verlag.
  2. De Melo Pereira, G. V., De Carvalho Neto, D. P., Magalhaes Junior, A. I., Vasquez, Z. S., Medeiros, A. B. P., Vandenberghe, L. P. S. & Soccol, C. R. 2019. Exploring the impacts of postharvest processing on the aroma formation of coffee beans - A review. Food Chemistry, 272, 441–452.
  3. Dong, W., Hu, R., Chu, Z., Zhao, J. & Tan, L. 2017. Effect of different drying techniques on bioactive components, fatty acid, composition and volatile profile of Robusta coffee beans. Food Chemistry, 234, 121–130.
  4. Flament, I. 2002. Coffee Flavour Chemistry (1st edition). England: John Wiley & Sons, Ltd.
  5. International Coffee Organization. 2017. Historical data on the global coffee trade (http://www.ico.org/historical/1990 onwards/PDF/1a-total-production.pdf). Last accessed on 12 October 2020.
  6. Pochont, N., Mohammad, M., Pradeep, B. & Kumar, V. 2020. A comparative study of drying kinetics and quality of Indian red chilli in solar hybrid greenhouse drying and open sun drying. Materialstoday: Proceedings, 21, 286–290.
  7. Rodríguez, Ó., Santacatalina, J. V., Simal, S., Garcia-Perez, J., Femenia, A. & Rosselló, C. 2014. Influence of power ultrasound application drying kinetic of apple and its antioxidant and microstructural properties. Journal of Food Engineering, 129, 21–29.
  8. Sekyere, C., Forson, F. & Adam, F. 2016. Experimental investigation of the drying characteristics of a mixed mode natural convection solar crop dryer with back up heater. Renewable Energy, 92, 532–542.
  9. Sfredo, M., Finzer, J. R. & Limaverde, J. 2005. Heat and mass transfer in coffee fruits drying. Journal of Food Engineering, 70, 15–25.
  10. Suherman, S., Widuri, H., Patricia, S., Susanto, E. E. & Sutrisna, R. J. 2020. Energy analysis of a hybrid solar dryer for drying coffee beans. International Journal of Renewable Energy Development, 9(1), 131–139.
  11. Vega-Galvez, A., Ah-Hen, K., Chacana, M., Vergara, J., Martinez-Monzo, J., Garcia-Segovia, P., Lemus-Mondaca, R. & Di Scala, K. 2012. Effect of temperature and air velocity on drying kinetics, antioxidant capacity, total phenolic content, colour, texture and microstructure of apple (var. Granny Smith) slices. Food Chemistry, 132(1), 51–59.