Characterisation of different treated whey protein concentrates by means of low-resolution nuclear magnetic resonance

In order to slow down the evolution and to minimise the extent of syneresis in dairy products the effect of new process steps and recipes on the structure of the final products were studied. The objective of this paper was to detect structural changes with regard to the water-immobilisation of differently treated whey protein concentrates (WPC) by means of nuclear magnetic resonance (NMR). The first measurements with pure WPC show obvious variations for the differently treated samples and the original native sample (a). (b) Denatured and (c) denatured and additionally sheared WPCs show not only an observably higher viscosity, but also shorter relaxation times. The fraction of the immobilised phase is about twice as high as in native WPC samples. These data reveal an improved water-holding capacity. (d) WPC samples mixed with cream and afterwards emulsified show a different behaviour with regard to their water-holding capacity during the evolution of the shearing process. The results suggest that for each treatment and/or change of the recipe the optimal shearing time has to be determined in order to achieve minimal relaxation times. These are obviously correlated with the highest water-holding capacity. The presented data indicate that NMR measurements are a useful technique to detect and analyse changes of the mobility of water and to identify fractions of differently bound/immobilised water phases of WPCs in dependence on the corresponding pretreatment and recipe, respectively. (C) 2004 Elsevier Ltd. All rights reserved.