An alkaline de-esterification method was developed to modify the functional properties of pectin extracted from soybean hull waste. The process yielded pectin with degrees of esterification (DE) ranging from 40 to 0.40, which was then incorporated into symmetrical supercapacitors using carbon active material derived from in situ resource utilization (ISRU) methods for space exploration applications. Physical characterization via Fourier transform infrared spectroscopy, H1 nuclear magnetic resonance spectroscopy, and static light scattering revealed that precipitation pH significantly influenced DE, molecular weight, and yield. In electrochemical testing using coin cells with blocking electrodes, pectin with 27 DE demonstrated superior ionic conductivity of 17.51 S m−1, substantially higher than reported biopolymer alternatives. While initial supercapacitor cells using ISRU carbon showed modest capacity (∼1 F g−1) and specific energy (∼0.1–1 Wh kg−1), devices incorporating commercial carbon electrodes achieved markedly improved performance (2–5 Wh kg−1). The pectin-based hydrogel electrolytes exhibited promising characteristics including high specific power (1,000–11,000 W kg−1) and exceptional stability over 10,000 galvanostatic charge-discharge cycles with maintained coulombic efficiency, establishing their potential for future energy storage applications.