Effect of κ-carrageenan on rheological properties, microstructure, texture and oxidative stability of water-in-oil spreads

The effect of kappa-carrageenan concentration (0-7.5 g kg(-1)) on the rheology, microstructure, texture and oxidative stability of water-in-oil (W/O) spreads (600 g fat kg(-1) emulsion) was examined over 60 days storage time. Results showed that increasing the kappa-carrageenan concentration to 7.5 g kg(-1) significantly increased the viscosity of the aqueous phase (to 42.7 mPa s at 60 degrees C) resulting in gelation of the aqueous phase on cooling. The microstructure of the spreads was disrupted by higher levels of kappa-carrageenan, resulting in a less homogeneous distribution of the aqueous phase. Melt temperature (where tan delta > 1) decreased significantly from 62 to 56.2 degrees C with increasing kappa-carrageenan concentration from 0 to 7.5 g kg(-1). The firmness and the G' at 6 degrees C for all samples were significantly increased after 60 days storage with only small effects due to kappa-carrageenan levels. Oxidation of the fat phase was evident by the significant increases in peroxide values of all spreads on storage, with kappa-carrageenan exhibiting no antioxidant behaviour. While increased kappa-carrageenan levels modified the microstructure of W/O spreads in terms of the droplet size of the aqueous phase and its distribution few changes were evident in the continuous fat phase. (C) 2009 Elsevier Ltd. All rights reserved.