(38c) Insights into Vibrational Rheology for Determining the Stickiness of Food Powders

Food powders are complex systems with diverse ingredient formulations, entailing numerous physicochemical interactions among particles, containers, and the surrounding environment. Industrial processes that handle such powders often encounter challenges related to their rheological properties. These properties are susceptible to environmental factors like relative humidity and temperature, which can lead to stickiness and caking phenomena, compromising storage and processing quality. Understanding and predicting stickiness in food powders is crucial for various stages of production and consumption. However, the field currently lacks standardized measurement techniques and predictability. Despite advancements in assessing powder stickiness over the past decades, persistent challenges remain in controlling environmental conditions during testing, accounting for surface phenomena sensitivity, and considering the kinetics of the process.

This study introduces a novel method for assessing powder stickiness by examining its kinetics, particularly focusing on the onset of stickiness ₍t_s) in amorphous food powders through rheology. The method utilizes a rheometer equipped with a shaker and a cell for in-situ moisture control, facilitating fast and automated assessment of powder flow behavior. By using rheology to identify the point at which the powder's elasticity and viscosity significantly increase, our method provides insights into the onset of stickiness.

In contrast to traditional devices requiring temperature adjustments and lengthy equilibration, our powder cell, equipped with humidity control, enables in-situ examination of water uptake at ambient temperature. Method validation extends across various powders, including glass beads, maltodextrins, and soluble coffee. Vibration within the system continuously reorganizes particles, improving measurement accuracy, ensuring homogeneity, and heightening sensitivity to surface properties.

Results demonstrate that powder stickiness is a complex kinetic phenomenon involving various surface and volume mechanisms, such as moisture diffusivity, plasticization, liquid bridge formation, and cohesion, dependent on both the powder's chemical (functionality, surface chemistry) and physical (particle size distribution, rugosity, and morphology) nature.

Our approach offers valuable insights for understanding and quantifying stickiness kinetics in food powders, potentially enhancing food processing and quality control. It operates efficiently, minimizing powder attrition, making it suitable for ambient conditions, and bridging the gap between the behavior of powder and environmental conditions in the food industry.