Enhancing the Physicochemical Properties of Porang Glucomannan Flour (Amorphophallus muelleri Blume) by Green Oxidants: Hydrogen Peroxide and Gaseous Ozone

Native glucomannan exhibits low solubility, therefore limiting its applications. Green oxidants such as hydrogen peroxide (H2O2) and gaseous ozone are commonly used to enhance the solubility of polysaccharides. This study aimed to investigate the impact of the two oxidants including varying the H2O2 concentrations (0.5%, 1%, 2%, and 4%) and gaseous ozone exposure times (30, 60, and 90 min) on the physicochemical characteristics (flow behavior, Fourier transform infrared spectroscopy (FTIR), whiteness, transparency, solubility, swelling power, water holding capacity, oil holding capacity, peroxide residue, and morphological properties) of oxidized porang glucomannan flour. Increasing H2O2 concentration and gaseous ozone exposure time reduced the viscosity and the pseudoplastic shear-thinning parameters. The FTIR results showed a peak at wavenumber of 1616 or 1612 cm−1 which is the identity peak of carboxyl groups, indicating that the oxidation reaction occurred. The peroxide and gaseous ozone oxidation increased the whiteness (78.88–83.05% and 79.26–79.46%), solubility (2.97–5.52% and 3.06–4.22%), water-holding capacity (25.46–29.02 and 24.42–24.87), and oil-holding capacity (2.21–2.42 and 2.15–2.26) while reducing swelling power (29.69–26.89% and 29.77–28.07%) values, respectively. The gel transparency increased with H2O2 oxidation (65.78–68.45%) but decreased with gaseous ozone oxidation (63.07–59.41%). The peroxide residue ranged from 0.0014 to 0.0115%, which is below the hazardous concentration and considered safe. Morphological analysis indicated that oxidation by H2O2 and gaseous ozone altered the surface of glucomannan particles to be damaged, brittle, and eroded. Overall, the properties of oxidized glucomannan produced by peroxide oxidation were superior to those obtained by gaseous ozone oxidation.