Swelling of food powders: Particle-size dependent swelling kinetics – experimental investigation and model-based evaluation

Swelling of food powders upon contact with water is a phenomenon with high relevance for powder reconstitution. Detailed knowledge about swelling kinetics of food powders and factors influencing these kinetics is key to improving product formulations and process conditions. This study focuses on the impact of particle size on swelling kinetics. Two food powders (gelatin powder and soy protein isolate) were studied regarding their maximum water uptake and swelling speed. Gelatin powder was analyzed using NMR (nuclear magnetic resonance) relaxometry, while soy protein isolate was investigated by laser diffraction. Kinetic models were used to determine swelling rate and maximum and equilibrium water uptake. For a non-dissolving material (gelatin powder), the swelling rate was found to decrease with increasing particle size, while the equilibrium water uptake was independent of size. For dissolving material (soy protein isolate), both the swelling rate and the maximum water uptake decreased with increasing size. The equilibrium water uptake was not correlated to particle size. • Investigation of particle size influence on swelling kinetics • Methods: laser diffraction and NMR relaxometry • Particle size influences swelling kinetics of food powders • Swelling rate decreases with size, equilibrium water uptake is independent of size • Maximum volume increase of partially dissolving material is size-dependent