Quantification of the compactibility of several protein isolates: Relationship between isolate physical-chemical properties and compaction properties

Despite their growing interest in the conception of several nutraceutical delivery systems including tablets, no work seem to deal with the tabletability of proteins. In this study, seven commercial isolates have been selected (soy and whey proteins) and the influence of their primary properties (protein type, protein content, humidity, and ash content) and secondary properties (particle size, shape and tap density) on their compactibility and compressibility were studied. Whey proteins seemed to show a better tabletability than soy proteins. Isolate density and humidity strongly affected proteins compactibility: powders with high density showed very low compactibility and a decrease of isolate water content strongly lowered powder compactibility, suggesting that liquid bridges may increase protein-protein interactions during compaction. Laser diffraction measurements/ microscopic observations showed that isolate particles would have the same size/shape, consequently, these properties did not show any influence on protein tabletability. At last, surprisingly, no clear relationship between compactibility and compressibility has been showed.