Design and synthesis of modified and resistant starch-based oil-in-water emulsions

In this study, rice starch was modified by different modifications that included debranching (DB), esterification with octenyl succinic anhydride (OSA), debranching followed by OSA modification (DBOS) and OSA modification followed by debranching (OSDB). Following modification, the resistant starch content and emulsifying properties of the modified starches markedly increased in comparison with the native starch with the DBOS starch having the highest resistant starch content and the best emulsifying properties. This can be attributed to its higher degree of OSA substitution resulting in an enhanced amphiphilic character and better emulsion stability. Microstructure, physical stability and rheological properties of oil-in-water emulsions using these modified rice starches were also investigated and it was observed that emulsions stabilized by OSA and DBOS starches exhibited smaller oil droplets, were more stable to creaming and possessed stronger three-dimensional structure when compared with the other modified starch-based emulsions. Since the DBOS starch was found to demonstrate the highest resistant starch content and better emulsifying properties than the other starches, it was then chosen for optimization of its concentration to give the best emulsion characteristics and stability. The emulsions stabilized by the DBOS starch at a concentration of 4% or 5% (w/w) were found to be more stable and very little phase separation was observed after a storage period of 30 days.