The use of a microhydrodynamic model, kinetic analysis and optimization tools for the development of corn starch nanosuspensions via wet-stirred media milling

Abstract

Starch micro and nanoparticles have emerged as popular stabilizers in food and pharmaceutical formulations. Wet-stirred media milling (WSMM) to develop such particles has not been widely reported, in contrast to chemical hydrolysis. Therefore, this contribution aimed to analyze the effects of: 1) Sodium dodecyl sulfate (SDS) and post-milling operations on the stability of starch nanosuspensions; 2) the bead diameter (d_b) (0.15, 0.50 mm) and starch concentration (c_S) (1, 3.5, 7 % w/v) on the type and stability of nanosuspensions, breakage kinetics and microhydrodynamic parameters; 3) spray-drying of nanosuspensions on the structural changes and redispersion of powders. Stable nanosuspensions with an average size of 161±5 nm could be obtained, from an initial size of 14.08±0.08 μm. The use of SDS as a stabilizer prevented aggregation during milling and allowed the formation of amylose-SDS complexes, supported by DSC and X-ray techniques. The microhydrodynamic analysis showed that increasing c_S decreased the compression forces applied to particles. Moreover, the intensity of collisions was improved with a larger d_b. Spray-dried nanosuspensions formulated with a c_S of 7 % (w/v), different SDS concentrations (0, 0.07 and 1 % w/v), and a d_b of 0.15 mm were analyzed. Submicron particles could only be obtained with 1 % (w/v) of SDS: from 366 to 271 nm after milling and spray-drying, respectively. Under these conditions, the granules were fully fragmented, which was confirmed by X-ray and TEM techniques. These results showed that WSMM could be implemented as a solvent-free methodology to obtain biopolymer-based nanoparticles.