Kinetic study of a conventional and ultrasound-assisted extraction of pectin from different plant-based side streams: Impact on pectin extraction yield, purity and molecular pectin structure

The time-dependency of both a conventional and ultrasound-assisted extraction (UAE) was studied for three biomasses, carrot pomace (CP), broccoli stems (BS) and pumpkin pomace (PP). Both extraction processes were performed completely analogous without and with ultrasound waves to unequivocally evaluate the effect of ultrasonication. Besides the pectin extraction yield (considering the yield and pectin purity), the composition and molecular structure of the extracted materials were also studied as a function of time. For all biomasses, UAE resulted in a(n) (slight) increase of the final pectin extraction yield, giving rise to the extraction of an additional 4.2, 5.8 and 10.7% of the amount of pectin initially present for CP, BS and PP, respectively. Prolonged extraction times resulted in pectin structures comparable to conventional extraction (with a higher protein content). Compared to conventional extraction, shorter UAE processes (1, 5 and 2.5 min for CP, BS and PP, respectively) resulted in comparable pectin extraction yields and slightly more branched pectin structures with a higher protein content. Both observations show the potential of UAE for the intensification of the industrial pectin extraction. The three biomasses differed mainly in the amount of non-pectic compounds co-extracted, and the sensitivity by which the UAE process was accelerated. [Display omitted] •Ultrasound-assisted extraction resulted in a slightly increased final pectin yield.•Shorter extraction processes could be used with ultrasound-assisted extraction.•Pectin structure differed only slightly between conventional and UAE processes.•Shorter processes, feasible with UAE, resulted in a more branched pectin structure.•Biomasses with a different composition resulted in different extents of co-extraction.