Optimization of microwave assisted extraction of pectin from sour orange peel and its physicochemical properties

• Pectin is extracted from sour orange peel using microwave assisted extraction.
• Box–Behnken design was used to model the yield and degree of esterification.
• Physicochemical properties of pectin extracted were investigated.
• Maximum extraction yield of pectin was achieved at 700 W for 3 min and pH 1.5.
• Sour orange peel pectin is classed as low methoxyl pectin.

Microwave assisted extraction technique was used to extract pectin from sour orange peel. Box–Behnken design was used to study the effect of irradiation time, microwave power and pH on the yield and degree of esterification (DE) of pectin. The results showed that the optimum conditions for the highest yield of pectin (29.1%) were obtained at pH of 1.50, microwave power of 700 W, and irradiation time of 3 min. DE values of pectin ranged from 1.7% to 37.5%, indicating that the obtained pectin was low in methoxyl. Under optimal conditions, the galacturonic acid content and emulsifying activity were 71.0 ± 0.8% and 40.7%, respectively. In addition, the emulsion stability value ranged from 72.1% to 83.4%. Viscosity measurement revealed that the solutions of pectin at low concentrations showed nearly Newtonian flow behavior, and as the concentration increased, pseudoplastic flow became dominant.