Starch thickening through structure and attractive electrostatics: Patchy charged colloidosomes

Advances in modified starches are needed to meet consumer and regulatory demands for label friendly, resilient thickeners. Starch-based patchy charged colloidosomes (PCCs) thicken uniquely through a combination of mechanisms providing an advantage over other modified starches. PCCs are hollow spheres composed of positively charged and negatively charged starch granules. PCCs were fabricated in three ratios of positive to negative starch granules: 1:9, 3:7, and 1:1. A positive colloidosome and a negative colloidosome were fabricated as non-patchy controls. Negatively charged starch granules were extracted from amaranth flour and positively charged starch was obtained by chemical modification with 2,3-epoxypropyltrimethylammonium chloride (ETMAC). PCCs were fabricated using a scalable, bottom-up, oil in water emulsion template. The physical arrangement of starch granules into hollow, spherical structures (~17–90 μm in diameter) increased solution viscosity through specific volume increase (4–7×). The PCCs were water-permeable and solutions thickened as the continuous phase decreased. In combination with the structural thickening, attraction between the positive and negative charges in the starch colloidosomes further contributed to enhanced viscosity. The hollow arrangement increased viscosity by 3–10× depending on charge ratio. The advantage of PCCs lies in their multi-mechanism thickening that leverages structure and electrostatic attractions to improve resilience to external stresses.