Emulsion stability of sugar beet pectin increased by genipin crosslinking

This work aimed to enhance the emulsifying properties of sugar beet pectin (SBP) by adopting a crosslinking strategy that covalently bridged the amino groups (–NH2) of lysine residues of the proteinaceous moiety using genipin (GP) as the crosslinker. Compared to control-SBP (C-SBP), GP crosslinked SBP (G-SBP) was larger in molecular weight (from 3.04 × 105 g/mol to 1.31 × 106 g/mol) and mean radius of gyration (from 34.8 nm to 39.2 nm), and showed a more compact conformation, as supported by analysis of high-performance size exclusion chromatography coupled with multiple angle light scattering (SEC-MALLS) and atomic force microscopy (AFM). G-SBP was featured by a new absorbance peak at ~595 nm, resulting in a distinct blue color of the aqueous solution. G-SBP suffered a slight decrease in interfacial properties and emulsifying activities in comparison to C-SBP, leading to a lower specific surface area and a larger volume-weighted mean diameter (d4,3) for the fresh emulsion. Nevertheless, the G-SBP stabilized emulsion was more stable than the C-SBP stabilized emulsion during storage for 21 d with d4,3 increasing from 0.541 μm and 0.425 μm to 0.625 μm and 1.66 μm for G-SBP and C-SBP, respectively. The improved emulsifying stability of G-SBP can be ascribed to the combination of the following two aspects: 1) G-SBP exerted a lager viscosity-enhancing effect to slow down droplet collision and flocculation; 2) the carbohydrate moiety of G-SBP formed a dense and compact hydrated layer providing strong steric stabilization for the oil droplets to resist flocculation and coalescence. Altogether, this work demonstrates that GP is a favorable agent to crosslink the side chains of SBP and modify its emulsification performance.