Tabletability of whey protein isolates

Whey protein isolates (WPIs) have recently been shown to be suitable as excipients for the formulation of oral controlled-release tablets. This contribution investigates the tabletability of six commercial WPI samples. The influence of primary (e.g., composition) and secondary (e.g., particle size, shape, porosity and density) properties on compactibility, compressibility and flowability of the isolates was studied. WPI tabletability strongly depended on particle size and shape. Isolates presenting the lowest particle size showed the highest compactibility. A decrease in particle size may thus induce an increase in the bridging surface area, leading to stronger tablets with higher mechanical strength. Water content and particle porosity were shown not to affect WPI tabletability. According to inert gas adsorption measurements, WPI samples were found to be mostly non-porous. All of the isolates showed good flow properties. Consequently, most of the WPIs studied could be suitable as excipients for manufacturing direct compression tablets.