The Utilization of Ethanol as Antisolvent to Enhance the Glucomannan Content of Tuber of Amorphophallus muelleri Blume

Abstract

Porang (Amorphophallus muelleri Blume) is widely found in Indonesia. The high Glucomannan (GM) content in Porang (Amorphophallus muelleri Blume) compared to other tubers becomes the main advantage of Porang. Glucomannan is a low-calorie fibre polysaccharide with a β-1,4 bond composed of D-glucose and D-mannose. However, its Calcium Oxalate (CaC2O4) content is an issue and should be minimized when consumed. The research focused on increasing the GM content of raw Porang tuber donated from PT ABS., Bogor. Initially, the raw material was roughly sliced and soaked in NaCl solution (10% or 15 %-w), washed with gently warm water (approx. 40 °C), and air dried to result in Crude Konjac Flour (CKF).
Further purification of CKF will produce Konjac Glucomannan (KGM). The KGM has a higher content of glucomannan. Ethanol (EtOH) was used as an antisolvent in the purification step. The final product of KGM was analyzed regarding GM, calcium oxide, moisture, and ash content. A 15%-w of NaCl solution followed by warm water washing could reduce the 59% content of Calcium Oxalate. Meanwhile, further purification using 50% EtOH increased 627.85% GM content from their initial value in Porang tubers. Hence, the treatment combination of NaCl-warm water washing and EtOH purification maximally removes calcium oxide and increases the GM content in the KGM.