Modulating Functionality of Starch-Based Patchy Particles by Manipulating Architecture and Environmental Factors

Starch as a food-grade thickener has been commonly used in food products to modulate textural properties. Improving viscosity-enhancing ability, so as to be able to use less starch for the same texture, has been considered as an approach to reduce the dietary consumption of carbohydrates. We have positively charged amaranth starch (∼1 μm) and negatively charged corn starch (>10 μm) and physically fused the particles together to create a starch with a heterogeneous pattern. This starch has a negatively charged main body, due to the larger corn particles, and positively charged patches from the amaranth starch. These patchy particles self-assembled through electrostatic interactions into a shear-reversible thickener. The impact of patchiness and charge density on material functionality was investigated. The degree of patchiness was controlled by manipulating the ratio between the two starches, and results showed that viscosity was reduced when the patchiness was higher. With the same patchy area, a higher charge density did not contribute to higher water-holding capacity. The more charged particles were able to enhance the viscosity, however, due to the stronger interparticle electrostatic interaction. The effects of environmental factors including pH level and ionic strength were also investigated, and the results showed that at extreme pH levels, or in the presence of Na+ or Ca2+, the charges on the starch particles were screened, and this inhibited interaction and reduced viscosity. The present work demonstrates that the texture of starch slurries can be fine-tuned by manipulating the degree of patchiness and the charge density of patchy particles. It also evaluates the application potential in food products with different pH levels and ionic strengths.