Whey proteins analysis in aqueous medium and in artificial gastric and intestinal fluids

Abstract

Whey proteins isolates (WPI) were treated in aqueous medium at various pH values. Zeta potential, turbidity and particle size measurement were determined as a function of pH. FTIR analysis was performed in ATR mode (attenuated total reflectance). Digestibility was assessed by treating whey proteins with artificial gastric and intestinal fluids. Proteolytic enzymes such as pepsin from porcine stomach mucosa was added in the gastric fluid. Pancreatin and trypsin from porcine and bile salts were added in the intestinal fluid. SDS-PAGE revealed hydrolysis of α-lactalbumin and bovine serum albumin by pepsin while β-lactoglobulin was not hydrolyzed by gastric fluid. All the proteins of WPI were easily hydrolyzed in the intestinal fluid. The zeta potential of WPI went from positive values to negative values as the pH was increased. Turbidity values indicated the presence of particles in the solution which were confirmed by the measurement of particle size. FTIR analysis determined the fingerprint of WPI macromolecule.