Abstract :
Objective: Porang or konjac is one type of tubers that are widely used in industry, food, cosmetics, and medical. Porang and Konjac contain glucomannan, a polysaccharide consisting of D-glucose and D-manosa.Materials and Methods: One way to determine the content is using phenol-concentrated sulfuric acid reagent with visible spectrophotometric method. Before determinate how much glucomannan in porang, the color stability test and method validation were performed. Results: From the color stability test, the absorbance was observed after 180 min. For the validation result, the selected wavelength was 492.0 nm, and the equation of regression was y = 0.0266x+0.0019 (r = 0.9992 > r table = 0.834) and Vxo 2.16%, while the precision gave the coefficient of variation 0.54% and accuracy gave average recovery for porang powder (99.60 ± 0.86% w/w) and konjac powder (100.48 ± 0.56% w/w). Conclusion: The determination of glucomannan was carried out in two samples, which were taken from Indonesia (porang powder) and China (konjac powder). The result showed that the concentration of glucomannan in porang powder was 52.33 ± 0.74% (w/w) and in konjac powder was 61.24 ± 0.60% (w/w).
Keyword :
Glucomannan (D-glucose and D-mannose), konjac powder (Amorphophallus konjac), phenol-sulfuric acid reagent, porang powder (Amorphophallus oncophyllus), validation method, visible spectrophotometry