Potentially bioactive and caffeine-loaded peptidic sub-micron and nanoscalar particles

Whey proteins were hydrolyzed with pepsin to antioxidant peptides, cross-linked by transglutaminase and then particulated through ethanol addition. Reducing power assay indicated that cross-linking enhanced the antioxidant activity of hydrolysate. Particles prepared from non-hydrolyzed protein, peptides and cross-linked peptides were all of bimodal size distribution comprised from sub-micron (>100 nm) and nanoscalar (<100 nm) populations. The enzymatic cross-linking resulted in generation of more monodisperse particles and increased the volume fraction of nano-sized population. Scanning electron microscopy revealed an almost spherical morphology for samples and Fourier transform infrared spectroscopy confirmed the cross-linking of peptides. Heat-scanning of samples by a differential scanning calorimeter indicated that cross-linking did not affect the thermal behavior of particles. However, a reinforcing effect on particles was suggested for cross-linking based on the in vitro tests carried out at various digestion media. Cross-linking slowed down the release rate of entrapped caffeine from particles in a simulated gastric fluid.