Structural, physicochemical, and emulsifying properties of pectin obtained by aqueous extraction from red pitaya (Hylocereus polyrhizus) peel

Abstract

This work aimed to carry out a straightforward aqueous extraction of pectin from red pitaya peels (RPP), in a drive to promote the circular economy of the settlements where the fruit of this endemic species grows. The average pectin yield was 11.59 g/100 g dry basis, the degree of esterification was 60.35±1.35% (classified as high methoxyl), the galacturonic acid content was 54.36±1.03%, and the protein content of 5.86 ± 0.25%. The RPP pectin was analyzed in terms of physicochemical, functional, and structural features. The FTIR spectrum confirmed that the unveiled pectin structure was consistent with that reported for commercial pectins from different botanical sources. Pectin aqueous dispersions exhibited power-law shear thinning behaviour. Corn oil (10 mL) in 150 mL aqueous pectin solutions (0.12, 0.15, 0.30, 0.60 and 0.90%, w/v) emulsions exhibited increasing emulsifying activity and emulsifying stability with increased pectin concentration. It was concluded that the RPP pectin is an alternative potential new source of pectin for use in the formation and stabilization of oil-in-water food emulsions.