Investigation of correlations between powder functionalities and powder surface properties for milk protein ingredients

Milk protein powders are widely used ingredient in processed food products, meanwhile, characterization of powder functionalities is of technical challenge to the manufacturers of ingredients and consumer foods. Rapid evaluation methods or indicators are needed to fill the mentioned technological gap. This study aimed to investigate correlations between a series of powder functionalities and powder surface properties, which may be characterized using a relative rapid method. Six types of milk protein powder with 2 different batches were used as samples in this study. The powder wettability was determined based on a modified International Dairy Federation method. Powder flowability was determined using the Warren Spring cohesion measured by rheometer. The dispersibility was indicated by the median particle size at a designated dispersing time point. Regarding the surface properties, the contact angle of powder samples was determined by the sessile drop method using both water and diiodomethane as reference liquids. Subsequently, surface free energy was computed through the Owens, Wendt, Rabel, and Kaelble model. Pearson correlation analysis revealed meaningful correlations between surface properties (e.g., surface free energy, cohesion work, and adhesion work) and powder functionality attributes (e.g., wettability and flowability). This study suggests that the wettability and flowability of milk protein powders can be indicated by powder surface energy-related parameter, such as work of cohesion.