Ultrasound-assisted enzymatic extraction of orange peel pectinand its characterisation

Abstract

Citrus processing waste (CPW) accumulates in vast amounts worldwide during fruit processing and its disposal through landfilling is environmentally damaging. However, CPW is also a renewable source of economically and medically relevant compounds such as pectin. There is a need for new methods of extracting pectin from CPW, as conventional methods are unsustainable. Therefore, this study proposed anew environmentally friendly method, which combines ultrasound cavitation with cellulase preparation, Celluclast) into one extraction procedure (UAE), and compared it to conventional acid extraction. The yield and productivity of each method were measured and the extracts were analysed for composition and structural characteristics. UAE and acid extraction pectin yields (26.9 vs. 22.1%) and productivity (0.10vs. 0.09%/min) values were comparable. The extracts consisted mainly of galacturonic acid and galactose residues, but the ratio was different for each method; 1: 0.34 and 0.84: 1 for acid and UAE-extracted pectin, respectively. FTIR was used to estimate the degree of esterification of the pectin extracts; 8% and55% for acid and UAE-extracted pectin, respectively. TGA revealed a higher ash content in UAE pectin, while XRD revealed similar degrees of polymer crystallinity. Viscosimetry revealed that the acid pectin had a higher molecular weight (70.22 kDa) compared to UAE pectin (197.78 kDa). In conclusion, the UAE procedure is a viable alternative to acid extraction.