Evaluation of I-optimal and Box–Behnken designs for green extraction of pectins using NADES from carrot pomace

This study investigates the use of natural deep eutectic solvents (NADES) for environmentally friendly extraction of pectic polysaccharides from carrot pomace, a low-cost agro-industrial byproduct. Two response surface methodologies, Box-Behnken design (BBD) and I-optimal design (IOD), were compared to optimize the extraction using a ternary NADES system composed of choline chloride, glucose, and citric acid (ChCl/Glc/CA). The IOD model showed superior predictive performance (R² = 0.95 for yield; R² = 0.81 for uronic acid content) and greater validity across a broader parameter range. Under optimal conditions, the IOD extraction yielded 20.1 % crude pectin with 73.5 % uronic acid, while BBD produced 20.4 % with 71.0 % uronic acid. Ion-exchange purification resulted in 72.7 % pectin fraction from the IOD extract (80.7 % galacturonic acid) and 93.3 % from the BBD extract (80.9 % galacturonic acid). Both fractions showed similar structural characteristics. The BBD-derived pectin was predominantly low-methyl-esterified homogalacturonan with minor rhamnogalacturonan I regions, while IOD-derived pectin showed slightly higher acidity and structural heterogeneity, suggesting stronger polymer-solvent interactions. These findings demonstrate the efficiency and selectivity of NADES-based extraction and support IOD as a robust strategy for modeling green biopolymer recovery processes from agricultural residues.