Influence of pH and heat treatment of whey on the functional properties of whey protein concentrates in yoghurt

Our aim was to investigate how two conditions of whey processing, pH and heat treatment, affect the physical properties of stirred yoghurts fortified to 45 g protein kg(-1) with whey protein concentrates (WPC). Cheddar whey was heated at pH 6.4 or pH 5.8 at 72 degrees C for 15 s, eventually heated further at 82 or 88 degrees C for 78 s, ultrafiltered, and spray dried. Resulting WPC contained 38% protein; the denaturation level of the whey protein was 10-53%. There were significant (P < 0.05) differences in physical properties of WPC fortified yoghurts: water-holding capacity ranged from 33% to 46% and elastic modulus ranged from 63 to 145 Pa depending on whey processing. WPC with low denaturation level produced yoghurts with high elastic modulus and water-holding capacity. Minimizing the heat treatment during whey processing maximized the functional properties of WPC to be used in yoghurt. (c) 2006 Elsevier Ltd. All rights reserved.