Impact of Varying Sodium Metabisulfite Levels on the Physicochemical Properties of

Porang ( Amorphophallus muelleri Blume) is an underutilized tuber with significant potential for food and non-food industries due to its high glucomannan content. However, postharvest management is challenging due to rapid discoloration and breakdown. This study aims to evaluate the impact of varying sodium metabisulfite concentration (1000, 1500, 2000 ppm) and soaking time (10, 15, 20 minutes) on the physicochemical and structural properties of porang chips and their derived flour. A split-plot design with three replications was employed, with significant differences assessed using Tukey's HSD test (95% Cl). The results showed that while higher concentrations significantly increased whiteness, they concurrently posed a critical food safety risk due to elevated sulfite residue. The optimal treatment was 1500 ppm Na₂S₂O₅ for 15 minutes, wich successfully yielded high quality (72.88% whiteness and 17.79% glucomannan) while maintaining a safe sulfite residue (40.57 mg/kg) well below the regulatory threshold (70 mg/kg) (SNI, 2020; BPOM, 2013). FTIR and SEM analyses further demonstrated that sodium metabisulfite effectively maintained the glucomannan structure and enhanced microstructural integrity. These findings suggested that mild sulfite pretreatment is an advantageous and effective approach for improving the characteristics and functional quality of porang chips intended for industrial utilization.