Improving Coffee Bean Drying Performance Using Polydryer (Dryer Assisted with Superabsorbent Polymer)

Superabsorbent polymer is a material that can swell hundreds to thousands of times after absorbing moisture. Studies that combined the use of this material in coffee bean drying have not yet been widely disclosed. In this study, a dryer assisted with superabsorbent polymer (Polydryer) was applied to improve the drying performance of coffee beans. The materials for superabsorbent polymer hydrogel (polygel) were cassava starch and acrylic acid. Based on this study, the use of polygel and heater was able to alleviate humidity while signifying the temperature inside the drying chamber. This condition certainly aided the drying process because it provided a greater driving force for free and bound water to diffuse from the inner coffee bean particle to the environment. Normal and intermittent drying modes were also carried out to compare the drying performance. The normal operation mode required 14 h to attain a product moisture content of below 12%. Meanwhile, the intermittent drying mode, where the heater operated merely in the initial stage, took 72 h to reach the maximal 12% product moisture content. Further improvement of the Polydryer was done by using three chambers arranged in series and operating in the normal mode, resulting in a more efficient drying system with a swifter process of 7 h. The results indicated that coffee bean drying using the Polydryer was effective and can be used to substitute conventional methods, especially during the night-time and rainy season. Besides, the dried coffee beans were free of insects, rot, mold, and foreign matter and were in a specialty grade category.