Effects of octenyl succinic anhydride groups distribution on the storage and shear stability of Pickering emulsions formulated by modified rice starch.

The modified rice starches by octenyl succinic anhydride (OS-RSs) with the same degree of substitution of 0.033 were prepared in aqueous solution using 3% or 20% (w/w) NaOH as a catalyst (OS-RS 3 or OS-RS 20). The results indicated that 20% of NaOH could destroy the structure of starch more seriously and led to more OS groups travelling to interior of starch granules. Furthermore, the storage stability and rheological properties of Pickering emulsions formulated by RS, OS-RS 3 and OS-RS 20 were investigated. Emulsion index of OS-RS 20 were always lower than OS-RS 3 during the storage time, while G', G" and viscosity of O/W Pickering emulsion formulated by OS-RS 20 particles were greater than those of OS-RS 3. OS-RS 3 with more hydrophobic groups in the granule surface could form more compact oil/water layers which contributed greater to the storage stability of Pickering emulsion due to the formation of more compact oil/water layers. However, OS-RS 20 with homogeneous distribution of OS groups in the whole particles resulted in the formation of a tighter droplet network structure that was more resistant to external impacts, which showed OS-RS 20 could improve the shear stability of Pickering emulsion.