Eggplant peel as a high potential source of high methylated pectin: Ultrasonic extraction optimization and characterization

Eggplant peel as a new source was used for pectin extraction using ultrasonic method. The extraction process factors were optimized using Box-Behnken design (BBD) and under optimal conditions (ultrasound power of 50 W, irradiation time of 30 min and pH of 1.5), the predicted extraction yield (35.36 g/100 g) was validated by the experimental results (33.64 ± 1.12 g/100 g). The eggplant peel pectin (EPP) was examined in terms of chemical, physicochemical, functional and structural features. The results indicated that the EPP was rich in galacturonic acid (66.08g/100 g), high in degree of esterification (61.22%) and total phenolic content, and low in ash and protein content. Also, EPP had a suitable value of water and oil holding capacity, emulsifying properties, antioxidant activity, and foam capacity. In addition, FT-IR and 1H NMR spectroscopy proved the existence of pectin structure in the obtained samples and XRD pattern suggested a high crystallinity in EPP.