Emulsion

Engineering

Small-angle X-ray scattering

Materials science

Chromatography

Scattering

Pectin

Chemical engineering

Food science

Physics

Extraction (chemistry)

Atomic force microscopy

Nanotechnology

Organic chemistry

Optics

Molecular dynamics

Alkali metal

Computational chemistry

Composite material

Rheology

Crystallography

Chemistry

Nanostructure

Carbohydrate Polymers

Structure and properties of pectin can be affected by extraction methods. In this study, grapefruit peel pectins extracted by HCl (at pH 1 [P1], 2 [P2], and 3 [P3]) and NaOH (at pH 9 [P9], 10 [P10], and 11 [P11]) were prepared and characterized. Atomic force microscopy (AFM) provided direct evidence of complex nano-structural patterns of pectins and revealed cross-linked networks of P10 and P11. Small-angle X-ray scattering (SAXS) demonstrated that P1, P2, and P3 possessed a relatively extended conformation, whereas P9, P10, and P11 displayed a three-dimensional structure and folded conformation. The compact and extended conformations of P3 contributed to its high viscosity in solution and the stability of the formed emulsion (75%). Porous surface and larger three-dimensional nanostructure (Dmax: 23 nm) of P10 facilitated its ion-binding capacity. Our results provide valuable insight into relationship between extraction methods and structure-properties of pectin, facilitating design of functional pectins.

The structure–property relationships of acid- and alkali-extracted grapefruit peel pectins