Characterization of pectin extracted from pomelo peel using pulsed ultrasound assisted extraction and acidic hot water extraction process

Abstract

In the present study, the characteristic properties namely XRD, FTIR, DSC, TGA and FESEM analyses of pectin extracted from pomelo fruit peel using pulsed ultrasound assisted extracted (PUUAE) were compared with those of pectin obtained with the conventional acidic hot water extraction (AHWE) process. The pectin extracted from PUUAE process has been analysed to possess better properties in comparison with the pectin obtained from the AHWE process. Pectin obtained from these two methods had been of high methoxyl pectin with almost similar structure. XRD analysis confirmed that AHWE based pectin possessed lower crystallinity than the PUUAE based pectin. The XRD spectra of PUUAE pectin affirmed sharper and stronger peaks than those of the AHWE based pectin and especially at 18.33° and 29.04° Further, the FTIR study revealed stronger absorption areas for PUUAE based pectin than those pertinent in the AHWE based pectin. This inferred that the pectin extracted with PUUAE had higher degree of esterification than that obtained with the AHWE process. Moreover, the DSC and TGA analyses indicated that PUUAE pectin had higher thermal stability in comparison to AHWE based pectin. The exothermic transition for the PUUAE based pectin was found to occur at higher temperature (245.7 °C) in comparison to the AHWE based pectin sample (239 °C). The TGA study conveyed double-stage decomposition for the PUUAE pectin sample (two DTGA peak temperatures (first at 230 °C and the second at 317 °C)) in comparison to the data obtained for the AHWE based pectin sample (a single peak only appears at 182 °C). The FESEM study affirmed a smoother surface with more structural integrity for PUUAE based pectin than that pertinent in the AHWE pectin sample. Therefore, the obtained characteristics can be inferred to the view that the PUUAE process is effective for the production of high quality pectin from pomelo peel (PP) for relevant functional applications.