Optimization of Pectin Extraction from Ramie by Orthogonal Methodology and Its Partial Physicochemical Properties

Pectin was extracted from Ramie [Boehmeria nivea (L.) Gaud] through ammonium oxalate extraction method. The influences of single factors (ammonium oxalate concentration, extraction time, solid–liquid ratio, and reaction temperature) on the yield of ramie pectin were studied. Orthogonal experiment was then performed to optimize the combination of the given conditions using pectin yield as the measuring indicator. Finally, the partial physicochemical properties of ramie pectin extracted in the optimal conditions were analyzed. Results showed that the optimal conditions for single-element experiment were 3.5 h (extraction time), 1:25 (solid–liquid ratio), 0.85% (concentration of ammonium oxalate) and 95 °C (extraction temperature), and that the optimal combination conditions for orthogonal experiment was 4 h, 1:30, 0.95% and 90 °C. The ramie pectin yield extracted in optimal conditions reached 15.81%, and its protein content, galacturonic acid content, and esterification degree were 0.659 mg/g, 49.92%, and 53.11%, respectively. Therefore, the proposed method was successfully applied to obtain ramie pectin and may provide scientific basis for improving the multi-utilization value of ramie.