Characterization of Pectin Extracted from Orange Peel Powder using Microwave-Assisted and Acid Extraction Methods

Pectin extracted from dried orange peel powder by microwave extraction method (MAE) and conventional acid extraction method (CE) were compared based on their yield, color, solubility in cold and hot water, equivalent weight, degree of esterification (DE), methoxyl percentage, and gelling properties. The raw orange peel powder of 98.95 µm size had moisture 8.33%, carbohydrate 80.06%, crude protein 5.6%, fat 2.3%, ash 3.62%, L* value 66.26 ± 0.05, a* value 11.89 ± 0.02, and b* value 60.56 ± 0.15, and poor flowability. The pectin yield in MAE (15.79%) was significantly higher than CE (8.78%); time taken for processing operation was 90 s and 15 min in MAE and CE, respectively. The equivalent weight of MAE and CE pectin were 485 mg/mL and 381 mg/mL, respectively. DE and methoxyl content of MAE and CE pectin were 42.85%, 35.48%, and 6.99% and 5.75%, respectively. The CIE L*, a* and b*, values of the MAE and CE pectin powders were 41.27, 7.11, and 31.41, and 37.54, 10.96, 24.34, respectively. Complex viscosity, storage modulus, and loss modulus of CE pectin was higher than that of MAE but were not significantly different (p > 0.05). The pectin gel obtained through both the methods showed a good stability.