Effects of Wet Extraction Parameters on Glucomannan Purity and Calcium Oxalate Reduction in Porang ( Amorphophallus oncophyllus ) Tuber Flour

Porang tuber is one of the commodities containing high glucomannan, which increases the body’s immunity and reduces cholesterol, blood sugar, and body weight. However, porang tubers contain calcium oxalate, which hurts the human body. The study aimed to define the effect of soaking ratio, solvent concentration, and processing time on the purification technique to obtain high‐purity flour and determine the best characteristics of porang flour. The porang tubers were extracted using the wet method, which consisted of the immersion ratio of adding sodium metabisulfite (Na 2 S 2 O 5 ) and sodium chloride (NaCl) with ethanol solvent at different extraction times. The research resulted in the treatment significantly affecting all observed parameters except fat content in porang glucomannan flour. In addition, the best characteristics were obtained from the treatment of a 1:3 soaking ratio, 96% ethanol concentration, and 120 min of extraction time, which showed a flour whiteness value of 99.38, oxalate of 0.10%, viscosity of 52,758.5 cP, and glucomannan content of 88% on dry basis. Considering the results of all parameters mentioned above, treating a 1:3 soaking ratio, 96% ethanol concentration, and 120 min of extraction time improves the yield and quality of glucomannan flour by decreasing calcium oxalate content by 0.37% from 0.47% to 0.10%. Porang flour with these characteristics is suitable as a thickener or a source of thickening food additives.