Pectin Recovery from Ri6 Durian ( Durio zibethinus ) Rind via Hot Citric-Acid Extraction

Abstract Ri6 Durian ( Durio zibethinus ) is highly nutritious, yet its peel, which constitutes a substantial portion of the fruit, is commonly discarded. This rind not only makes up a large mass fraction but is also a rich source of pectin. This study examined how extraction parameters, including acid concentration (0.1, 0.3, 0.5, and 0.8 M citric acid; pH 1.5, 1.6, 1.9, and 2.2), solid-to-solvent ratio (1:10, 1:20, 1:30, and 1:40 g/mL), temperature (70–90 °C), and extraction time (30–120 min), affect pectin yield from the rind. The best conditions (1:20 g/mL raw material to solvent, 0.5 M citric acid at pH 1.6, 80 °C, 60 min) yielded a pectin recovery of 23%. The extracted pectin displayed high purity (anhydrouronic acid, 78.26 ± 0.54%) and a low degree of esterification (30.44 ± 1.57%). Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and thermogravimetric analysis (TGA) confirmed the product’s structural, morphological and thermal stability integrity. An early-stage techno-economic assessment (TEA) using lab-scale data indicated strong economic feasibility, with unit production costs significantly below market price (831 USD/t vs. 8,000 USD/t). Sensitivity analysis confirmed robustness across realistic scenarios. These findings underscore the significant potential for sustainable biorefinery development and circular economy applications utilizing durian processing residues in Southeast Asia.