Preparation of starch derivatives using reactive extrusion and evaluation of modified starches as shell materials for encapsulation of flavoring agents by spray drying

Acetylated, n-octenylsuccinylated (n-OSA) and phosphorylated waxy maize starches were prepared using reactive extrusion in a single-screw extruder. The starches were hydrolyzed with hydrochloric acid (3.4% dry basis, at 50 °C for 6 h) before they were esterified. n-OSA starch and acetylated starch were conventionally modified in a slurry and further hydrolyzed using a single-screw extruder. Starch phosphate was prepared by a conventional method in a slurry and by extrusion. Chemical modifications of n-OSA and acetylated starches were confirmed using Infrared Spectroscopy. The degree of substitution (DS), viscosity profile, water solubility index (WSI), and water absorption index (WAI) were measured to the modified starches. The viscosity of the modified starches was reduced after extrusion and the WSI and WAI increased. Microcapsules were produced by spray drying. n-OSA starch exhibited good emulsifying capabilities and a total oil retention (% w/w) of 94.75%, better than the control oil retention (commercial N-LOK) of 89.16%. Starch phosphates and acetates registered oil retentions of 55.75% and 61.31%, respectively. The modified starches prepared using reactive extrusion showed good characteristics as shell materials for encapsulation by spray drying.