Influence of ultrasound-assisted extraction on the pectin extraction yield and structural characteristics: A case study on carrot pomace (Daucus carota)

For the ultrasound-assisted extraction (UAE) of pectin from carrot pomace, the influence of different extraction parameters on the pectin yield and structure was studied. Therefore, an Orthogonal Minimally Aliased Response Surface (OMARS) design and a constant extraction temperature were used. This study showed that pH had the most pronounced effect on the pectin yield and molecular structure, and that a low pH is crucial to liberate pectin from the cell wall matrix. Besides, it was shown that an increased pectin yield can be achieved with an increased ultrasound intensity, provided that the pH is sufficiently low. The optimal UAE conditions resulted in a pectin yield of 57.2 %, while the control extraction, which used the same extraction conditions without the application of ultrasound waves, only resulted in a pectin yield of 37.4 %, showing a significant increase with ultrasonication. Due to the temperature-control during the ultrasonication process, this increased yield can be attributed to the ultrasound waves as such, and not to the accompanying temperature increase. Additionally, shorter extraction times can be used to obtain pectin yields comparable to a conventional acid extraction process. These increased yields and shorter extraction processes show the potential of UAE as an alternative extraction technology.