Effect of high-pressure treatment on the electrospray ionization mass spectrometry (ESI-MS) profiles of whey proteins

The effects of different high-pressure (HP) treatments (pressures ranging between 450 and 650 MPa) on beta-lactoglobulin and alpha-lactalbumin and on two commercial whey protein isolates (WPI) were examined by electrospray ionization mass spectrometry (ESIMS). HP treatment resulted in substantial changes in the charge-state distribution (CSD) of pure fl-lactoglobulin, attributable to exposure of side chains of buried amino acids to solvent, whereas the CSD of pure a-lactalbumin was largely insensitive to HP treatment. The changes in the CSD of these proteins effected by HP treatment differed between the two commercial WPI samples examined, perhaps due to the different production methodologies employed by the two suppliers. These findings illustrate the important role of interactions between the various components in WPI in the response of whey proteins to HP treatment and underscore the difficulty of obtaining consistent rheological and nutraceutical properties by HP treatment of WPI particularly when different sources of WPI are employed. The information provided by ESIMS may be useful in monitoring the effects of HP treatment to verify that such consistency is achieved. (C) 2007 Elsevier Ltd. All rights reserved.