Diffusing wave spectroscopy and rheological studies of rennet-induced gelation of skim milk in the presence of pectin and κ-carrageenan

The effect of the presence of kappa-carrageenan on casein micelle stability and their rennet-induced aggregation was studied using diffusing wave spectroscopy and rheology measurements. Different concentrations of kappa-carrageenan, below the gelation regime, were added to skim milk at pH 6.7. No changes in casein stability and on the aggregation kinetics of casein micelles were observed at kappa-carrageenan concentrations <0.015% (w/v). The effect of mixing different concentrations of high methoxyl pectin (HMP) (0.04, 0.12 and 0.18%, w/v) with 0.015% (w/v) kappa-carrageenan in skim milk was then studied. It was observed that kappa-carrageenan protects the system from HMP-induced destabilization. The study of the synergistic effect of kappa-carrageenan and HMP on the structuring of casein micelles in milk opens new avenues for the development and control of processes where different mechanisms of aggregation and destabilization occur simultaneously. (C) 2009 Elsevier Ltd. All rights reserved.