High internal phase emulsions stabilized by starch nanocrystals

Abstract There is increasing interest in the development of Pickering emulsions stabilized by food grade (nano) particles, due to their promising applications in food formulations. The work reports for the first time that starch nanocrystals (SNCs) prepared by sulfuric acid hydrolysis from native waxy maize starch exhibit a great potential to act as sole effective stabilizer for oil-in-water high internal phase emulsions (HIPEs). Relative to the native starch, the SNCs had more irregular and agglomerated morphology, and significantly higher crystallinity and hydrophobicity. The particle size and ζ -potential of the SNCs considerably varied with pH and/or ionic strength. The formation, microstructure and properties of stable HIPEs were characterized by visual observations, optical microscopy and dynamic oscillary measurements. The results indicated that at a given particle concentration in the continuous phase (1.0 wt%), stable and gel-like HIPEs were formed at oil internal phase ( ϕ ) values of 0.75–0.85; increasing the particle concentration led to the formation of gel-like HIPEs with stronger stiffness; in the absence of NaCl, stable and gel-like HIPEs were formed only at pH values of 5.0–10.0, and increasing the pH persistently decreased the emulsion size (and accordingly, increased the gel stiffness); increasing the ionic strength from 0 to 400 mM resulted in a progressive impairment of the emulsification performance, as well as of the formation of stable HIPEs. The findings would be of great relevance for the development of HIPEs stabilized by SNCs appropriate to be applied in the food formulations.