Effect of pH and ionic strength on the emulsifying properties of two Octenylsuccinate starches in comparison with gum Arabic

Octenylsuccinate starches were obtained by combining esterification reaction and β-amylase hydrolysis treatment with (HOSE) and without (OSE) acid pretreatment. In the present study, the emulsions stabilized by gum Arabic (GA), OSE and HOSE starches were systematically compared in terms of molecular structure and emulsion properties. The molecular structure of three emulsifiers was analyzed using size exclusion chromatography, showing that the GA had a relative smaller molecular size distribution compared to OSE and HOSE starches. Emulsifying activity index (EAI), emulsifying stability index (ESI), droplet size (d4,3) of emulsions at different emulsifier to oil ratios were determined to evaluate the emulsion properties of three emulsifiers under a wide range of pH and NaCl concentration. The GA stabilized emulsion showed the lowest droplet size at high emulsifier concentrations, but clear phase separation was observed after 7 days of storage at relatively low emulsifier concentrations (1:9 and 0.5:9.5). The emulsions stabilized by the HOSE starch showed excellent emulsion stability under a wide range of pH and NaCl concentration, and produced the small droplets with better storage stability, particularly at relatively low emulsifier concentrations (1:9 and 0.5:9.5).